1 files changed, 886 insertions, 28 deletions

diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
index 3a68cf38a6b3..143b3e72c25e 100644
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -17,19 +17,34 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+#include <linux/bitmap.h>
 #include <linux/bottom_half.h>
+#include <linux/bug.h>
+#include <linux/cache.h>
+#include <linux/compat.h>
 #include <linux/cpu.h>
 #include <linux/cpu_pm.h>
 #include <linux/kernel.h>
+#include <linux/linkage.h>
+#include <linux/irqflags.h>
 #include <linux/init.h>
 #include <linux/percpu.h>
+#include <linux/prctl.h>
 #include <linux/preempt.h>
+#include <linux/prctl.h>
+#include <linux/ptrace.h>
 #include <linux/sched/signal.h>
+#include <linux/sched/task_stack.h>
 #include <linux/signal.h>
+#include <linux/slab.h>
+#include <linux/sysctl.h>
 
 #include <asm/fpsimd.h>
 #include <asm/cputype.h>
 #include <asm/simd.h>
+#include <asm/sigcontext.h>
+#include <asm/sysreg.h>
+#include <asm/traps.h>
 
 #define FPEXC_IOF	(1 << 0)
 #define FPEXC_DZF	(1 << 1)
@@ -39,6 +54,8 @@
 #define FPEXC_IDF	(1 << 7)
 
 /*
+ * (Note: in this discussion, statements about FPSIMD apply equally to SVE.)
+ *
  * In order to reduce the number of times the FPSIMD state is needlessly saved
  * and restored, we need to keep track of two things:
  * (a) for each task, we need to remember which CPU was the last one to have
@@ -99,10 +116,741 @@
  */
 static DEFINE_PER_CPU(struct fpsimd_state *, fpsimd_last_state);
 
+/* Default VL for tasks that don't set it explicitly: */
+static int sve_default_vl = -1;
+
+#ifdef CONFIG_ARM64_SVE
+
+/* Maximum supported vector length across all CPUs (initially poisoned) */
+int __ro_after_init sve_max_vl = -1;
+/* Set of available vector lengths, as vq_to_bit(vq): */
+static __ro_after_init DECLARE_BITMAP(sve_vq_map, SVE_VQ_MAX);
+static void __percpu *efi_sve_state;
+
+#else /* ! CONFIG_ARM64_SVE */
+
+/* Dummy declaration for code that will be optimised out: */
+extern __ro_after_init DECLARE_BITMAP(sve_vq_map, SVE_VQ_MAX);
+extern void __percpu *efi_sve_state;
+
+#endif /* ! CONFIG_ARM64_SVE */
+
+/*
+ * Call __sve_free() directly only if you know task can't be scheduled
+ * or preempted.
+ */
+static void __sve_free(struct task_struct *task)
+{
+	kfree(task->thread.sve_state);
+	task->thread.sve_state = NULL;
+}
+
+static void sve_free(struct task_struct *task)
+{
+	WARN_ON(test_tsk_thread_flag(task, TIF_SVE));
+
+	__sve_free(task);
+}
+
+
+/* Offset of FFR in the SVE register dump */
+static size_t sve_ffr_offset(int vl)
+{
+	return SVE_SIG_FFR_OFFSET(sve_vq_from_vl(vl)) - SVE_SIG_REGS_OFFSET;
+}
+
+static void *sve_pffr(struct task_struct *task)
+{
+	return (char *)task->thread.sve_state +
+		sve_ffr_offset(task->thread.sve_vl);
+}
+
+static void change_cpacr(u64 val, u64 mask)
+{
+	u64 cpacr = read_sysreg(CPACR_EL1);
+	u64 new = (cpacr & ~mask) | val;
+
+	if (new != cpacr)
+		write_sysreg(new, CPACR_EL1);
+}
+
+static void sve_user_disable(void)
+{
+	change_cpacr(0, CPACR_EL1_ZEN_EL0EN);
+}
+
+static void sve_user_enable(void)
+{
+	change_cpacr(CPACR_EL1_ZEN_EL0EN, CPACR_EL1_ZEN_EL0EN);
+}
+
+/*
+ * TIF_SVE controls whether a task can use SVE without trapping while
+ * in userspace, and also the way a task's FPSIMD/SVE state is stored
+ * in thread_struct.
+ *
+ * The kernel uses this flag to track whether a user task is actively
+ * using SVE, and therefore whether full SVE register state needs to
+ * be tracked.  If not, the cheaper FPSIMD context handling code can
+ * be used instead of the more costly SVE equivalents.
+ *
+ *  * TIF_SVE set:
+ *
+ *    The task can execute SVE instructions while in userspace without
+ *    trapping to the kernel.
+ *
+ *    When stored, Z0-Z31 (incorporating Vn in bits[127:0] or the
+ *    corresponding Zn), P0-P15 and FFR are encoded in in
+ *    task->thread.sve_state, formatted appropriately for vector
+ *    length task->thread.sve_vl.
+ *
+ *    task->thread.sve_state must point to a valid buffer at least
+ *    sve_state_size(task) bytes in size.
+ *
+ *    During any syscall, the kernel may optionally clear TIF_SVE and
+ *    discard the vector state except for the FPSIMD subset.
+ *
+ *  * TIF_SVE clear:
+ *
+ *    An attempt by the user task to execute an SVE instruction causes
+ *    do_sve_acc() to be called, which does some preparation and then
+ *    sets TIF_SVE.
+ *
+ *    When stored, FPSIMD registers V0-V31 are encoded in
+ *    task->fpsimd_state; bits [max : 128] for each of Z0-Z31 are
+ *    logically zero but not stored anywhere; P0-P15 and FFR are not
+ *    stored and have unspecified values from userspace's point of
+ *    view.  For hygiene purposes, the kernel zeroes them on next use,
+ *    but userspace is discouraged from relying on this.
+ *
+ *    task->thread.sve_state does not need to be non-NULL, valid or any
+ *    particular size: it must not be dereferenced.
+ *
+ *  * FPSR and FPCR are always stored in task->fpsimd_state irrespctive of
+ *    whether TIF_SVE is clear or set, since these are not vector length
+ *    dependent.
+ */
+
+/*
+ * Update current's FPSIMD/SVE registers from thread_struct.
+ *
+ * This function should be called only when the FPSIMD/SVE state in
+ * thread_struct is known to be up to date, when preparing to enter
+ * userspace.
+ *
+ * Softirqs (and preemption) must be disabled.
+ */
+static void task_fpsimd_load(void)
+{
+	WARN_ON(!in_softirq() && !irqs_disabled());
+
+	if (system_supports_sve() && test_thread_flag(TIF_SVE))
+		sve_load_state(sve_pffr(current),
+			       &current->thread.fpsimd_state.fpsr,
+			       sve_vq_from_vl(current->thread.sve_vl) - 1);
+	else
+		fpsimd_load_state(&current->thread.fpsimd_state);
+
+	if (system_supports_sve()) {
+		/* Toggle SVE trapping for userspace if needed */
+		if (test_thread_flag(TIF_SVE))
+			sve_user_enable();
+		else
+			sve_user_disable();
+
+		/* Serialised by exception return to user */
+	}
+}
+
+/*
+ * Ensure current's FPSIMD/SVE storage in thread_struct is up to date
+ * with respect to the CPU registers.
+ *
+ * Softirqs (and preemption) must be disabled.
+ */
+static void task_fpsimd_save(void)
+{
+	WARN_ON(!in_softirq() && !irqs_disabled());
+
+	if (!test_thread_flag(TIF_FOREIGN_FPSTATE)) {
+		if (system_supports_sve() && test_thread_flag(TIF_SVE)) {
+			if (WARN_ON(sve_get_vl() != current->thread.sve_vl)) {
+				/*
+				 * Can't save the user regs, so current would
+				 * re-enter user with corrupt state.
+				 * There's no way to recover, so kill it:
+				 */
+				force_signal_inject(
+					SIGKILL, 0, current_pt_regs(), 0);
+				return;
+			}
+
+			sve_save_state(sve_pffr(current),
+				       &current->thread.fpsimd_state.fpsr);
+		} else
+			fpsimd_save_state(&current->thread.fpsimd_state);
+	}
+}
+
+/*
+ * Helpers to translate bit indices in sve_vq_map to VQ values (and
+ * vice versa).  This allows find_next_bit() to be used to find the
+ * _maximum_ VQ not exceeding a certain value.
+ */
+
+static unsigned int vq_to_bit(unsigned int vq)
+{
+	return SVE_VQ_MAX - vq;
+}
+
+static unsigned int bit_to_vq(unsigned int bit)
+{
+	if (WARN_ON(bit >= SVE_VQ_MAX))
+		bit = SVE_VQ_MAX - 1;
+
+	return SVE_VQ_MAX - bit;
+}
+
+/*
+ * All vector length selection from userspace comes through here.
+ * We're on a slow path, so some sanity-checks are included.
+ * If things go wrong there's a bug somewhere, but try to fall back to a
+ * safe choice.
+ */
+static unsigned int find_supported_vector_length(unsigned int vl)
+{
+	int bit;
+	int max_vl = sve_max_vl;
+
+	if (WARN_ON(!sve_vl_valid(vl)))
+		vl = SVE_VL_MIN;
+
+	if (WARN_ON(!sve_vl_valid(max_vl)))
+		max_vl = SVE_VL_MIN;
+
+	if (vl > max_vl)
+		vl = max_vl;
+
+	bit = find_next_bit(sve_vq_map, SVE_VQ_MAX,
+			    vq_to_bit(sve_vq_from_vl(vl)));
+	return sve_vl_from_vq(bit_to_vq(bit));
+}
+
+#ifdef CONFIG_SYSCTL
+
+static int sve_proc_do_default_vl(struct ctl_table *table, int write,
+				  void __user *buffer, size_t *lenp,
+				  loff_t *ppos)
+{
+	int ret;
+	int vl = sve_default_vl;
+	struct ctl_table tmp_table = {
+		.data = &vl,
+		.maxlen = sizeof(vl),
+	};
+
+	ret = proc_dointvec(&tmp_table, write, buffer, lenp, ppos);
+	if (ret || !write)
+		return ret;
+
+	/* Writing -1 has the special meaning "set to max": */
+	if (vl == -1) {
+		/* Fail safe if sve_max_vl wasn't initialised */
+		if (WARN_ON(!sve_vl_valid(sve_max_vl)))
+			vl = SVE_VL_MIN;
+		else
+			vl = sve_max_vl;
+
+		goto chosen;
+	}
+
+	if (!sve_vl_valid(vl))
+		return -EINVAL;
+
+	vl = find_supported_vector_length(vl);
+chosen:
+	sve_default_vl = vl;
+	return 0;
+}
+
+static struct ctl_table sve_default_vl_table[] = {
+	{
+		.procname	= "sve_default_vector_length",
+		.mode		= 0644,
+		.proc_handler	= sve_proc_do_default_vl,
+	},
+	{ }
+};
+
+static int __init sve_sysctl_init(void)
+{
+	if (system_supports_sve())
+		if (!register_sysctl("abi", sve_default_vl_table))
+			return -EINVAL;
+
+	return 0;
+}
+
+#else /* ! CONFIG_SYSCTL */
+static int __init sve_sysctl_init(void) { return 0; }
+#endif /* ! CONFIG_SYSCTL */
+
+#define ZREG(sve_state, vq, n) ((char *)(sve_state) +		\
+	(SVE_SIG_ZREG_OFFSET(vq, n) - SVE_SIG_REGS_OFFSET))
+
+/*
+ * Transfer the FPSIMD state in task->thread.fpsimd_state to
+ * task->thread.sve_state.
+ *
+ * Task can be a non-runnable task, or current.  In the latter case,
+ * softirqs (and preemption) must be disabled.
+ * task->thread.sve_state must point to at least sve_state_size(task)
+ * bytes of allocated kernel memory.
+ * task->thread.fpsimd_state must be up to date before calling this function.
+ */
+static void fpsimd_to_sve(struct task_struct *task)
+{
+	unsigned int vq;
+	void *sst = task->thread.sve_state;
+	struct fpsimd_state const *fst = &task->thread.fpsimd_state;
+	unsigned int i;
+
+	if (!system_supports_sve())
+		return;
+
+	vq = sve_vq_from_vl(task->thread.sve_vl);
+	for (i = 0; i < 32; ++i)
+		memcpy(ZREG(sst, vq, i), &fst->vregs[i],
+		       sizeof(fst->vregs[i]));
+}
+
+/*
+ * Transfer the SVE state in task->thread.sve_state to
+ * task->thread.fpsimd_state.
+ *
+ * Task can be a non-runnable task, or current.  In the latter case,
+ * softirqs (and preemption) must be disabled.
+ * task->thread.sve_state must point to at least sve_state_size(task)
+ * bytes of allocated kernel memory.
+ * task->thread.sve_state must be up to date before calling this function.
+ */
+static void sve_to_fpsimd(struct task_struct *task)
+{
+	unsigned int vq;
+	void const *sst = task->thread.sve_state;
+	struct fpsimd_state *fst = &task->thread.fpsimd_state;
+	unsigned int i;
+
+	if (!system_supports_sve())
+		return;
+
+	vq = sve_vq_from_vl(task->thread.sve_vl);
+	for (i = 0; i < 32; ++i)
+		memcpy(&fst->vregs[i], ZREG(sst, vq, i),
+		       sizeof(fst->vregs[i]));
+}
+
+#ifdef CONFIG_ARM64_SVE
+
+/*
+ * Return how many bytes of memory are required to store the full SVE
+ * state for task, given task's currently configured vector length.
+ */
+size_t sve_state_size(struct task_struct const *task)
+{
+	return SVE_SIG_REGS_SIZE(sve_vq_from_vl(task->thread.sve_vl));
+}
+
+/*
+ * Ensure that task->thread.sve_state is allocated and sufficiently large.
+ *
+ * This function should be used only in preparation for replacing
+ * task->thread.sve_state with new data.  The memory is always zeroed
+ * here to prevent stale data from showing through: this is done in
+ * the interest of testability and predictability: except in the
+ * do_sve_acc() case, there is no ABI requirement to hide stale data
+ * written previously be task.
+ */
+void sve_alloc(struct task_struct *task)
+{
+	if (task->thread.sve_state) {
+		memset(task->thread.sve_state, 0, sve_state_size(current));
+		return;
+	}
+
+	/* This is a small allocation (maximum ~8KB) and Should Not Fail. */
+	task->thread.sve_state =
+		kzalloc(sve_state_size(task), GFP_KERNEL);
+
+	/*
+	 * If future SVE revisions can have larger vectors though,
+	 * this may cease to be true:
+	 */
+	BUG_ON(!task->thread.sve_state);
+}
+
+
+/*
+ * Ensure that task->thread.sve_state is up to date with respect to
+ * the user task, irrespective of when SVE is in use or not.
+ *
+ * This should only be called by ptrace.  task must be non-runnable.
+ * task->thread.sve_state must point to at least sve_state_size(task)
+ * bytes of allocated kernel memory.
+ */
+void fpsimd_sync_to_sve(struct task_struct *task)
+{
+	if (!test_tsk_thread_flag(task, TIF_SVE))
+		fpsimd_to_sve(task);
+}
+
+/*
+ * Ensure that task->thread.fpsimd_state is up to date with respect to
+ * the user task, irrespective of whether SVE is in use or not.
+ *
+ * This should only be called by ptrace.  task must be non-runnable.
+ * task->thread.sve_state must point to at least sve_state_size(task)
+ * bytes of allocated kernel memory.
+ */
+void sve_sync_to_fpsimd(struct task_struct *task)
+{
+	if (test_tsk_thread_flag(task, TIF_SVE))
+		sve_to_fpsimd(task);
+}
+
+/*
+ * Ensure that task->thread.sve_state is up to date with respect to
+ * the task->thread.fpsimd_state.
+ *
+ * This should only be called by ptrace to merge new FPSIMD register
+ * values into a task for which SVE is currently active.
+ * task must be non-runnable.
+ * task->thread.sve_state must point to at least sve_state_size(task)
+ * bytes of allocated kernel memory.
+ * task->thread.fpsimd_state must already have been initialised with
+ * the new FPSIMD register values to be merged in.
+ */
+void sve_sync_from_fpsimd_zeropad(struct task_struct *task)
+{
+	unsigned int vq;
+	void *sst = task->thread.sve_state;
+	struct fpsimd_state const *fst = &task->thread.fpsimd_state;
+	unsigned int i;
+
+	if (!test_tsk_thread_flag(task, TIF_SVE))
+		return;
+
+	vq = sve_vq_from_vl(task->thread.sve_vl);
+
+	memset(sst, 0, SVE_SIG_REGS_SIZE(vq));
+
+	for (i = 0; i < 32; ++i)
+		memcpy(ZREG(sst, vq, i), &fst->vregs[i],
+		       sizeof(fst->vregs[i]));
+}
+
+int sve_set_vector_length(struct task_struct *task,
+			  unsigned long vl, unsigned long flags)
+{
+	if (flags & ~(unsigned long)(PR_SVE_VL_INHERIT |
+				     PR_SVE_SET_VL_ONEXEC))
+		return -EINVAL;
+
+	if (!sve_vl_valid(vl))
+		return -EINVAL;
+
+	/*
+	 * Clamp to the maximum vector length that VL-agnostic SVE code can
+	 * work with.  A flag may be assigned in the future to allow setting
+	 * of larger vector lengths without confusing older software.
+	 */
+	if (vl > SVE_VL_ARCH_MAX)
+		vl = SVE_VL_ARCH_MAX;
+
+	vl = find_supported_vector_length(vl);
+
+	if (flags & (PR_SVE_VL_INHERIT |
+		     PR_SVE_SET_VL_ONEXEC))
+		task->thread.sve_vl_onexec = vl;
+	else
+		/* Reset VL to system default on next exec: */
+		task->thread.sve_vl_onexec = 0;
+
+	/* Only actually set the VL if not deferred: */
+	if (flags & PR_SVE_SET_VL_ONEXEC)
+		goto out;
+
+	if (vl == task->thread.sve_vl)
+		goto out;
+
+	/*
+	 * To ensure the FPSIMD bits of the SVE vector registers are preserved,
+	 * write any live register state back to task_struct, and convert to a
+	 * non-SVE thread.
+	 */
+	if (task == current) {
+		local_bh_disable();
+
+		task_fpsimd_save();
+		set_thread_flag(TIF_FOREIGN_FPSTATE);
+	}
+
+	fpsimd_flush_task_state(task);
+	if (test_and_clear_tsk_thread_flag(task, TIF_SVE))
+		sve_to_fpsimd(task);
+
+	if (task == current)
+		local_bh_enable();
+
+	/*
+	 * Force reallocation of task SVE state to the correct size
+	 * on next use:
+	 */
+	sve_free(task);
+
+	task->thread.sve_vl = vl;
+
+out:
+	if (flags & PR_SVE_VL_INHERIT)
+		set_tsk_thread_flag(task, TIF_SVE_VL_INHERIT);
+	else
+		clear_tsk_thread_flag(task, TIF_SVE_VL_INHERIT);
+
+	return 0;
+}
+
+/*
+ * Encode the current vector length and flags for return.
+ * This is only required for prctl(): ptrace has separate fields
+ *
+ * flags are as for sve_set_vector_length().
+ */
+static int sve_prctl_status(unsigned long flags)
+{
+	int ret;
+
+	if (flags & PR_SVE_SET_VL_ONEXEC)
+		ret = current->thread.sve_vl_onexec;
+	else
+		ret = current->thread.sve_vl;
+
+	if (test_thread_flag(TIF_SVE_VL_INHERIT))
+		ret |= PR_SVE_VL_INHERIT;
+
+	return ret;
+}
+
+/* PR_SVE_SET_VL */
+int sve_set_current_vl(unsigned long arg)
+{
+	unsigned long vl, flags;
+	int ret;
+
+	vl = arg & PR_SVE_VL_LEN_MASK;
+	flags = arg & ~vl;
+
+	if (!system_supports_sve())
+		return -EINVAL;
+
+	ret = sve_set_vector_length(current, vl, flags);
+	if (ret)
+		return ret;
+
+	return sve_prctl_status(flags);
+}
+
+/* PR_SVE_GET_VL */
+int sve_get_current_vl(void)
+{
+	if (!system_supports_sve())
+		return -EINVAL;
+
+	return sve_prctl_status(0);
+}
+
+/*
+ * Bitmap for temporary storage of the per-CPU set of supported vector lengths
+ * during secondary boot.
+ */
+static DECLARE_BITMAP(sve_secondary_vq_map, SVE_VQ_MAX);
+
+static void sve_probe_vqs(DECLARE_BITMAP(map, SVE_VQ_MAX))
+{
+	unsigned int vq, vl;
+	unsigned long zcr;
+
+	bitmap_zero(map, SVE_VQ_MAX);
+
+	zcr = ZCR_ELx_LEN_MASK;
+	zcr = read_sysreg_s(SYS_ZCR_EL1) & ~zcr;
+
+	for (vq = SVE_VQ_MAX; vq >= SVE_VQ_MIN; --vq) {
+		write_sysreg_s(zcr | (vq - 1), SYS_ZCR_EL1); /* self-syncing */
+		vl = sve_get_vl();
+		vq = sve_vq_from_vl(vl); /* skip intervening lengths */
+		set_bit(vq_to_bit(vq), map);
+	}
+}
+
+void __init sve_init_vq_map(void)
+{
+	sve_probe_vqs(sve_vq_map);
+}
+
+/*
+ * If we haven't committed to the set of supported VQs yet, filter out
+ * those not supported by the current CPU.
+ */
+void sve_update_vq_map(void)
+{
+	sve_probe_vqs(sve_secondary_vq_map);
+	bitmap_and(sve_vq_map, sve_vq_map, sve_secondary_vq_map, SVE_VQ_MAX);
+}
+
+/* Check whether the current CPU supports all VQs in the committed set */
+int sve_verify_vq_map(void)
+{
+	int ret = 0;
+
+	sve_probe_vqs(sve_secondary_vq_map);
+	bitmap_andnot(sve_secondary_vq_map, sve_vq_map, sve_secondary_vq_map,
+		      SVE_VQ_MAX);
+	if (!bitmap_empty(sve_secondary_vq_map, SVE_VQ_MAX)) {
+		pr_warn("SVE: cpu%d: Required vector length(s) missing\n",
+			smp_processor_id());
+		ret = -EINVAL;
+	}
+
+	return ret;
+}
+
+static void __init sve_efi_setup(void)
+{
+	if (!IS_ENABLED(CONFIG_EFI))
+		return;
+
+	/*
+	 * alloc_percpu() warns and prints a backtrace if this goes wrong.
+	 * This is evidence of a crippled system and we are returning void,
+	 * so no attempt is made to handle this situation here.
+	 */
+	if (!sve_vl_valid(sve_max_vl))
+		goto fail;
+
+	efi_sve_state = __alloc_percpu(
+		SVE_SIG_REGS_SIZE(sve_vq_from_vl(sve_max_vl)), SVE_VQ_BYTES);
+	if (!efi_sve_state)
+		goto fail;
+
+	return;
+
+fail:
+	panic("Cannot allocate percpu memory for EFI SVE save/restore");
+}
+
+/*
+ * Enable SVE for EL1.
+ * Intended for use by the cpufeatures code during CPU boot.
+ */
+int sve_kernel_enable(void *__always_unused p)
+{
+	write_sysreg(read_sysreg(CPACR_EL1) | CPACR_EL1_ZEN_EL1EN, CPACR_EL1);
+	isb();
+
+	return 0;
+}
+
+void __init sve_setup(void)
+{
+	u64 zcr;
+
+	if (!system_supports_sve())
+		return;
+
+	/*
+	 * The SVE architecture mandates support for 128-bit vectors,
+	 * so sve_vq_map must have at least SVE_VQ_MIN set.
+	 * If something went wrong, at least try to patch it up:
+	 */
+	if (WARN_ON(!test_bit(vq_to_bit(SVE_VQ_MIN), sve_vq_map)))
+		set_bit(vq_to_bit(SVE_VQ_MIN), sve_vq_map);
+
+	zcr = read_sanitised_ftr_reg(SYS_ZCR_EL1);
+	sve_max_vl = sve_vl_from_vq((zcr & ZCR_ELx_LEN_MASK) + 1);
+
+	/*
+	 * Sanity-check that the max VL we determined through CPU features
+	 * corresponds properly to sve_vq_map.  If not, do our best:
+	 */
+	if (WARN_ON(sve_max_vl != find_supported_vector_length(sve_max_vl)))
+		sve_max_vl = find_supported_vector_length(sve_max_vl);
+
+	/*
+	 * For the default VL, pick the maximum supported value <= 64.
+	 * VL == 64 is guaranteed not to grow the signal frame.
+	 */
+	sve_default_vl = find_supported_vector_length(64);
+
+	pr_info("SVE: maximum available vector length %u bytes per vector\n",
+		sve_max_vl);
+	pr_info("SVE: default vector length %u bytes per vector\n",
+		sve_default_vl);
+
+	sve_efi_setup();
+}
+
+/*
+ * Called from the put_task_struct() path, which cannot get here
+ * unless dead_task is really dead and not schedulable.
+ */
+void fpsimd_release_task(struct task_struct *dead_task)
+{
+	__sve_free(dead_task);
+}
+
+#endif /* CONFIG_ARM64_SVE */
+
+/*
+ * Trapped SVE access
+ *
+ * Storage is allocated for the full SVE state, the current FPSIMD
+ * register contents are migrated across, and TIF_SVE is set so that
+ * the SVE access trap will be disabled the next time this task
+ * reaches ret_to_user.
+ *
+ * TIF_SVE should be clear on entry: otherwise, task_fpsimd_load()
+ * would have disabled the SVE access trap for userspace during
+ * ret_to_user, making an SVE access trap impossible in that case.
+ */
+asmlinkage void do_sve_acc(unsigned int esr, struct pt_regs *regs)
+{
+	/* Even if we chose not to use SVE, the hardware could still trap: */
+	if (unlikely(!system_supports_sve()) || WARN_ON(is_compat_task())) {
+		force_signal_inject(SIGILL, ILL_ILLOPC, regs, 0);
+		return;
+	}
+
+	sve_alloc(current);
+
+	local_bh_disable();
+
+	task_fpsimd_save();
+	fpsimd_to_sve(current);
+
+	/* Force ret_to_user to reload the registers: */
+	fpsimd_flush_task_state(current);
+	set_thread_flag(TIF_FOREIGN_FPSTATE);
+
+	if (test_and_set_thread_flag(TIF_SVE))
+		WARN_ON(1); /* SVE access shouldn't have trapped */
+
+	local_bh_enable();
+}
+
 /*
  * Trapped FP/ASIMD access.
  */
-void do_fpsimd_acc(unsigned int esr, struct pt_regs *regs)
+asmlinkage void do_fpsimd_acc(unsigned int esr, struct pt_regs *regs)
 {
 	/* TODO: implement lazy context saving/restoring */
 	WARN_ON(1);
@@ -111,7 +859,7 @@ void do_fpsimd_acc(unsigned int esr, struct pt_regs *regs)
 /*
  * Raise a SIGFPE for the current process.
  */
-void do_fpsimd_exc(unsigned int esr, struct pt_regs *regs)
+asmlinkage void do_fpsimd_exc(unsigned int esr, struct pt_regs *regs)
 {
 	siginfo_t info;
 	unsigned int si_code = 0;
@@ -144,8 +892,8 @@ void fpsimd_thread_switch(struct task_struct *next)
 	 * the registers is in fact the most recent userland FPSIMD state of
 	 * 'current'.
 	 */
-	if (current->mm && !test_thread_flag(TIF_FOREIGN_FPSTATE))
-		fpsimd_save_state(&current->thread.fpsimd_state);
+	if (current->mm)
+		task_fpsimd_save();
 
 	if (next->mm) {
 		/*
@@ -159,16 +907,16 @@ void fpsimd_thread_switch(struct task_struct *next)
 
 		if (__this_cpu_read(fpsimd_last_state) == st
 		    && st->cpu == smp_processor_id())
-			clear_ti_thread_flag(task_thread_info(next),
-					     TIF_FOREIGN_FPSTATE);
+			clear_tsk_thread_flag(next, TIF_FOREIGN_FPSTATE);
 		else
-			set_ti_thread_flag(task_thread_info(next),
-					   TIF_FOREIGN_FPSTATE);
+			set_tsk_thread_flag(next, TIF_FOREIGN_FPSTATE);
 	}
 }
 
 void fpsimd_flush_thread(void)
 {
+	int vl, supported_vl;
+
 	if (!system_supports_fpsimd())
 		return;
 
@@ -176,6 +924,42 @@ void fpsimd_flush_thread(void)
 
 	memset(&current->thread.fpsimd_state, 0, sizeof(struct fpsimd_state));
 	fpsimd_flush_task_state(current);
+
+	if (system_supports_sve()) {
+		clear_thread_flag(TIF_SVE);
+		sve_free(current);
+
+		/*
+		 * Reset the task vector length as required.
+		 * This is where we ensure that all user tasks have a valid
+		 * vector length configured: no kernel task can become a user
+		 * task without an exec and hence a call to this function.
+		 * By the time the first call to this function is made, all
+		 * early hardware probing is complete, so sve_default_vl
+		 * should be valid.
+		 * If a bug causes this to go wrong, we make some noise and
+		 * try to fudge thread.sve_vl to a safe value here.
+		 */
+		vl = current->thread.sve_vl_onexec ?
+			current->thread.sve_vl_onexec : sve_default_vl;
+
+		if (WARN_ON(!sve_vl_valid(vl)))
+			vl = SVE_VL_MIN;
+
+		supported_vl = find_supported_vector_length(vl);
+		if (WARN_ON(supported_vl != vl))
+			vl = supported_vl;
+
+		current->thread.sve_vl = vl;
+
+		/*
+		 * If the task is not set to inherit, ensure that the vector
+		 * length will be reset by a subsequent exec:
+		 */
+		if (!test_thread_flag(TIF_SVE_VL_INHERIT))
+			current->thread.sve_vl_onexec = 0;
+	}
+
 	set_thread_flag(TIF_FOREIGN_FPSTATE);
 
 	local_bh_enable();
@@ -191,14 +975,23 @@ void fpsimd_preserve_current_state(void)
 		return;
 
 	local_bh_disable();
-
-	if (!test_thread_flag(TIF_FOREIGN_FPSTATE))
-		fpsimd_save_state(&current->thread.fpsimd_state);
-
+	task_fpsimd_save();
 	local_bh_enable();
 }
 
 /*
+ * Like fpsimd_preserve_current_state(), but ensure that
+ * current->thread.fpsimd_state is updated so that it can be copied to
+ * the signal frame.
+ */
+void fpsimd_signal_preserve_current_state(void)
+{
+	fpsimd_preserve_current_state();
+	if (system_supports_sve() && test_thread_flag(TIF_SVE))
+		sve_to_fpsimd(current);
+}
+
+/*
  * Load the userland FPSIMD state of 'current' from memory, but only if the
  * FPSIMD state already held in the registers is /not/ the most recent FPSIMD
  * state of 'current'
@@ -213,7 +1006,7 @@ void fpsimd_restore_current_state(void)
 	if (test_and_clear_thread_flag(TIF_FOREIGN_FPSTATE)) {
 		struct fpsimd_state *st = &current->thread.fpsimd_state;
 
-		fpsimd_load_state(st);
+		task_fpsimd_load();
 		__this_cpu_write(fpsimd_last_state, st);
 		st->cpu = smp_processor_id();
 	}
@@ -233,7 +1026,12 @@ void fpsimd_update_current_state(struct fpsimd_state *state)
 
 	local_bh_disable();
 
-	fpsimd_load_state(state);
+	if (system_supports_sve() && test_thread_flag(TIF_SVE)) {
+		current->thread.fpsimd_state = *state;
+		fpsimd_to_sve(current);
+	}
+	task_fpsimd_load();
+
 	if (test_and_clear_thread_flag(TIF_FOREIGN_FPSTATE)) {
 		struct fpsimd_state *st = &current->thread.fpsimd_state;
 
@@ -252,6 +1050,33 @@ void fpsimd_flush_task_state(struct task_struct *t)
 	t->thread.fpsimd_state.cpu = NR_CPUS;
 }
 
+static inline void fpsimd_flush_cpu_state(void)
+{
+	__this_cpu_write(fpsimd_last_state, NULL);
+}
+
+/*
+ * Invalidate any task SVE state currently held in this CPU's regs.
+ *
+ * This is used to prevent the kernel from trying to reuse SVE register data
+ * that is detroyed by KVM guest enter/exit.  This function should go away when
+ * KVM SVE support is implemented.  Don't use it for anything else.
+ */
+#ifdef CONFIG_ARM64_SVE
+void sve_flush_cpu_state(void)
+{
+	struct fpsimd_state *const fpstate = __this_cpu_read(fpsimd_last_state);
+	struct task_struct *tsk;
+
+	if (!fpstate)
+		return;
+
+	tsk = container_of(fpstate, struct task_struct, thread.fpsimd_state);
+	if (test_tsk_thread_flag(tsk, TIF_SVE))
+		fpsimd_flush_cpu_state();
+}
+#endif /* CONFIG_ARM64_SVE */
+
 #ifdef CONFIG_KERNEL_MODE_NEON
 
 DEFINE_PER_CPU(bool, kernel_neon_busy);
@@ -286,11 +1111,13 @@ void kernel_neon_begin(void)
 	__this_cpu_write(kernel_neon_busy, true);
 
 	/* Save unsaved task fpsimd state, if any: */
-	if (current->mm && !test_and_set_thread_flag(TIF_FOREIGN_FPSTATE))
-		fpsimd_save_state(&current->thread.fpsimd_state);
+	if (current->mm) {
+		task_fpsimd_save();
+		set_thread_flag(TIF_FOREIGN_FPSTATE);
+	}
 
 	/* Invalidate any task state remaining in the fpsimd regs: */
-	__this_cpu_write(fpsimd_last_state, NULL);
+	fpsimd_flush_cpu_state();
 
 	preempt_disable();
 
@@ -321,8 +1148,11 @@ void kernel_neon_end(void)
 }
 EXPORT_SYMBOL(kernel_neon_end);
 
+#ifdef CONFIG_EFI
+
 static DEFINE_PER_CPU(struct fpsimd_state, efi_fpsimd_state);
 static DEFINE_PER_CPU(bool, efi_fpsimd_state_used);
+static DEFINE_PER_CPU(bool, efi_sve_state_used);
 
 /*
  * EFI runtime services support functions
@@ -348,10 +1178,24 @@ void __efi_fpsimd_begin(void)
 
 	WARN_ON(preemptible());
 
-	if (may_use_simd())
+	if (may_use_simd()) {
 		kernel_neon_begin();
-	else {
-		fpsimd_save_state(this_cpu_ptr(&efi_fpsimd_state));
+	} else {
+		/*
+		 * If !efi_sve_state, SVE can't be in use yet and doesn't need
+		 * preserving:
+		 */
+		if (system_supports_sve() && likely(efi_sve_state)) {
+			char *sve_state = this_cpu_ptr(efi_sve_state);
+
+			__this_cpu_write(efi_sve_state_used, true);
+
+			sve_save_state(sve_state + sve_ffr_offset(sve_max_vl),
+				       &this_cpu_ptr(&efi_fpsimd_state)->fpsr);
+		} else {
+			fpsimd_save_state(this_cpu_ptr(&efi_fpsimd_state));
+		}
+
 		__this_cpu_write(efi_fpsimd_state_used, true);
 	}
 }
@@ -364,12 +1208,26 @@ void __efi_fpsimd_end(void)
 	if (!system_supports_fpsimd())
 		return;
 
-	if (__this_cpu_xchg(efi_fpsimd_state_used, false))
-		fpsimd_load_state(this_cpu_ptr(&efi_fpsimd_state));
-	else
+	if (!__this_cpu_xchg(efi_fpsimd_state_used, false)) {
 		kernel_neon_end();
+	} else {
+		if (system_supports_sve() &&
+		    likely(__this_cpu_read(efi_sve_state_used))) {
+			char const *sve_state = this_cpu_ptr(efi_sve_state);
+
+			sve_load_state(sve_state + sve_ffr_offset(sve_max_vl),
+				       &this_cpu_ptr(&efi_fpsimd_state)->fpsr,
+				       sve_vq_from_vl(sve_get_vl()) - 1);
+
+			__this_cpu_write(efi_sve_state_used, false);
+		} else {
+			fpsimd_load_state(this_cpu_ptr(&efi_fpsimd_state));
+		}
+	}
 }
 
+#endif /* CONFIG_EFI */
+
 #endif /* CONFIG_KERNEL_MODE_NEON */
 
 #ifdef CONFIG_CPU_PM
@@ -378,9 +1236,9 @@ static int fpsimd_cpu_pm_notifier(struct notifier_block *self,
 {
 	switch (cmd) {
 	case CPU_PM_ENTER:
-		if (current->mm && !test_thread_flag(TIF_FOREIGN_FPSTATE))
-			fpsimd_save_state(&current->thread.fpsimd_state);
-		this_cpu_write(fpsimd_last_state, NULL);
+		if (current->mm)
+			task_fpsimd_save();
+		fpsimd_flush_cpu_state();
 		break;
 	case CPU_PM_EXIT:
 		if (current->mm)
@@ -438,6 +1296,6 @@ static int __init fpsimd_init(void)
 	if (!(elf_hwcap & HWCAP_ASIMD))
 		pr_notice("Advanced SIMD is not implemented\n");
 
-	return 0;
+	return sve_sysctl_init();
 }
-late_initcall(fpsimd_init);
+core_initcall(fpsimd_init);