KVM: ARM: Hypervisor initialization

Sets up KVM code to handle all exceptions taken to Hyp mode.

When the kernel is booted in Hyp mode, calling an hvc instruction with r0
pointing to the new vectors, the HVBAR is changed to the the vector pointers.
This allows subsystems (like KVM here) to execute code in Hyp-mode with the
MMU disabled.

We initialize other Hyp-mode registers and enables the MMU for Hyp-mode from
the id-mapped hyp initialization code. Afterwards, the HVBAR is changed to
point to KVM Hyp vectors used to catch guest faults and to switch to Hyp mode
to perform a world-switch into a KVM guest.

Also provides memory mapping code to map required code pages, data structures,
and I/O regions  accessed in Hyp mode at the same virtual address as the host
kernel virtual addresses, but which conforms to the architectural requirements
for translations in Hyp mode. This interface is added in arch/arm/kvm/arm_mmu.c
and comprises:
 - create_hyp_mappings(from, to);
 - create_hyp_io_mappings(from, to, phys_addr);
 - free_hyp_pmds();

Reviewed-by: Will Deacon <will.deacon@arm.com>
Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <c.dall@virtualopensystems.com>

1 files changed, 62 insertions, 0 deletions

diff --git a/arch/arm/kvm/interrupts.S b/arch/arm/kvm/interrupts.S
index 1dc8926e26d2..d10a8075409a 100644
--- a/arch/arm/kvm/interrupts.S
+++ b/arch/arm/kvm/interrupts.S
@@ -15,5 +15,67 @@
  * along with this program; if not, write to the Free Software
  * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
  */
+
+#include <linux/linkage.h>
+#include <linux/const.h>
+#include <asm/unified.h>
+#include <asm/page.h>
 #include <asm/asm-offsets.h>
 #include <asm/kvm_asm.h>
+#include <asm/kvm_arm.h>
+
+	.text
+
+__kvm_hyp_code_start:
+	.globl __kvm_hyp_code_start
+
+/********************************************************************
+ * Flush per-VMID TLBs
+ */
+ENTRY(__kvm_flush_vm_context)
+	bx	lr
+ENDPROC(__kvm_flush_vm_context)
+
+/********************************************************************
+ *  Hypervisor world-switch code
+ */
+ENTRY(__kvm_vcpu_run)
+	bx	lr
+
+/********************************************************************
+ *  Call function in Hyp mode
+ *
+ *
+ * u64 kvm_call_hyp(void *hypfn, ...);
+ *
+ * This is not really a variadic function in the classic C-way and care must
+ * be taken when calling this to ensure parameters are passed in registers
+ * only, since the stack will change between the caller and the callee.
+ *
+ * Call the function with the first argument containing a pointer to the
+ * function you wish to call in Hyp mode, and subsequent arguments will be
+ * passed as r0, r1, and r2 (a maximum of 3 arguments in addition to the
+ * function pointer can be passed).  The function being called must be mapped
+ * in Hyp mode (see init_hyp_mode in arch/arm/kvm/arm.c).  Return values are
+ * passed in r0 and r1.
+ *
+ * The calling convention follows the standard AAPCS:
+ *   r0 - r3: caller save
+ *   r12:     caller save
+ *   rest:    callee save
+ */
+ENTRY(kvm_call_hyp)
+	hvc	#0
+	bx	lr
+
+/********************************************************************
+ * Hypervisor exception vector and handlers
+ */
+
+	.align 5
+__kvm_hyp_vector:
+	.globl __kvm_hyp_vector
+	nop
+
+__kvm_hyp_code_end:
+	.globl	__kvm_hyp_code_end