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authorMarc Zyngier <maz@kernel.org>2020-07-31 19:38:23 +0200
committerCatalin Marinas <catalin.marinas@arm.com>2020-08-21 12:39:56 +0200
commitd49f7d7376d0c0daf8680984a37bd07581ac7d38 (patch)
tree393b2ffb2e6cf8f7594a37955a15e60571238f33 /arch/arm64
parentLinux 5.9-rc1 (diff)
downloadlinux-d49f7d7376d0c0daf8680984a37bd07581ac7d38.tar.xz
linux-d49f7d7376d0c0daf8680984a37bd07581ac7d38.zip
arm64: Move handling of erratum 1418040 into C code
Instead of dealing with erratum 1418040 on each entry and exit, let's move the handling to __switch_to() instead, which has several advantages: - It can be applied when it matters (switching between 32 and 64 bit tasks). - It is written in C (yay!) - It can rely on static keys rather than alternatives Signed-off-by: Marc Zyngier <maz@kernel.org> Tested-by: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org> Reviewed-by: Stephen Boyd <swboyd@chromium.org> Acked-by: Will Deacon <will@kernel.org> Link: https://lore.kernel.org/r/20200731173824.107480-2-maz@kernel.org Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'arch/arm64')
-rw-r--r--arch/arm64/kernel/entry.S21
-rw-r--r--arch/arm64/kernel/process.c34
2 files changed, 34 insertions, 21 deletions
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 2646178c8329..55af8b504b65 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -170,19 +170,6 @@ alternative_cb_end
stp x28, x29, [sp, #16 * 14]
.if \el == 0
- .if \regsize == 32
- /*
- * If we're returning from a 32-bit task on a system affected by
- * 1418040 then re-enable userspace access to the virtual counter.
- */
-#ifdef CONFIG_ARM64_ERRATUM_1418040
-alternative_if ARM64_WORKAROUND_1418040
- mrs x0, cntkctl_el1
- orr x0, x0, #2 // ARCH_TIMER_USR_VCT_ACCESS_EN
- msr cntkctl_el1, x0
-alternative_else_nop_endif
-#endif
- .endif
clear_gp_regs
mrs x21, sp_el0
ldr_this_cpu tsk, __entry_task, x20
@@ -294,14 +281,6 @@ alternative_else_nop_endif
tst x22, #PSR_MODE32_BIT // native task?
b.eq 3f
-#ifdef CONFIG_ARM64_ERRATUM_1418040
-alternative_if ARM64_WORKAROUND_1418040
- mrs x0, cntkctl_el1
- bic x0, x0, #2 // ARCH_TIMER_USR_VCT_ACCESS_EN
- msr cntkctl_el1, x0
-alternative_else_nop_endif
-#endif
-
#ifdef CONFIG_ARM64_ERRATUM_845719
alternative_if ARM64_WORKAROUND_845719
#ifdef CONFIG_PID_IN_CONTEXTIDR
diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index 84ec630b8ab5..b63ce4c54cfe 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -516,6 +516,39 @@ static void entry_task_switch(struct task_struct *next)
}
/*
+ * ARM erratum 1418040 handling, affecting the 32bit view of CNTVCT.
+ * Assuming the virtual counter is enabled at the beginning of times:
+ *
+ * - disable access when switching from a 64bit task to a 32bit task
+ * - enable access when switching from a 32bit task to a 64bit task
+ */
+static void erratum_1418040_thread_switch(struct task_struct *prev,
+ struct task_struct *next)
+{
+ bool prev32, next32;
+ u64 val;
+
+ if (!(IS_ENABLED(CONFIG_ARM64_ERRATUM_1418040) &&
+ cpus_have_const_cap(ARM64_WORKAROUND_1418040)))
+ return;
+
+ prev32 = is_compat_thread(task_thread_info(prev));
+ next32 = is_compat_thread(task_thread_info(next));
+
+ if (prev32 == next32)
+ return;
+
+ val = read_sysreg(cntkctl_el1);
+
+ if (!next32)
+ val |= ARCH_TIMER_USR_VCT_ACCESS_EN;
+ else
+ val &= ~ARCH_TIMER_USR_VCT_ACCESS_EN;
+
+ write_sysreg(val, cntkctl_el1);
+}
+
+/*
* Thread switching.
*/
__notrace_funcgraph struct task_struct *__switch_to(struct task_struct *prev,
@@ -530,6 +563,7 @@ __notrace_funcgraph struct task_struct *__switch_to(struct task_struct *prev,
entry_task_switch(next);
uao_thread_switch(next);
ssbs_thread_switch(next);
+ erratum_1418040_thread_switch(prev, next);
/*
* Complete any pending TLB or cache maintenance on this CPU in case