On world switch, we save the pointer to the current vcpu on the top
of the stack. This tends to complicate the exit path a bit as we then
need to dig into the stack to restore it (we've already pushed a number
of registers on top of it at that time), not to mention error prone.
A obvious way to simplify this is to use the HTPIDR register, which is an
architected method to store per-CPU data in HYP mode, and this is
exactly what this patch does.
Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx>
---
arch/arm/kvm/interrupts.S | 21 +++++++++++++--------
1 files changed, 13 insertions(+), 8 deletions(-)
diff --git a/arch/arm/kvm/interrupts.S b/arch/arm/kvm/interrupts.S
index 7fb0ab9..ac680b80 100644
--- a/arch/arm/kvm/interrupts.S
+++ b/arch/arm/kvm/interrupts.S
@@ -502,11 +502,18 @@ ENDPROC(__kvm_flush_vm_context)
mcr p15, 4, r2, c1, c1, 0
.endm
+.macro load_vcpu reg
+ mrc p15, 4, \reg, c13, c0, 2 @ HTPIDR
+.endm
+
@ Arguments:
@ r0: pointer to vcpu struct
ENTRY(__kvm_vcpu_run)
hvc #0 @ switch to hyp-mode
+ @ Save the vcpu pointer
+ mcr p15, 4, r0, c13, c0, 2 @ HTPIDR
+
@ Now we're in Hyp-mode and lr_usr, spsr_hyp are on the stack
mrs r2, sp_usr
push {r2} @ Push r13_usr
@@ -535,8 +542,6 @@ ENTRY(__kvm_vcpu_run)
VFPFMXR FPEXC, r2 @ VMSR
#endif
- push {r0} @ Push the VCPU pointer
-
@ Configure Hyp-role
configure_hyp_role 1, r0
@@ -707,7 +712,7 @@ after_vfp_restore:
@ the vcpu pointer and stuff off the stack and keep our fingers crossed
beq 99f
mov r0, #\exception_code
- pop {r1} @ Load VCPU pointer
+ load_vcpu r1 @ Load VCPU pointer
.if \exception_code == ARM_EXCEPTION_DATA_ABORT
mrc p15, 4, r2, c5, c2, 0 @ HSR
mrc p15, 4, r3, c6, c0, 0 @ HDFAR
@@ -831,13 +836,12 @@ host_switch_to_hyp:
mov pc, lr
guest_trap:
- ldr r1, [sp, #12] @ Load VCPU pointer
+ load_vcpu r1 @ Load VCPU pointer
str r0, [r1, #VCPU_HSR]
add r1, r1, #VCPU_USR_REG(3)
stmia r1, {r3-r12}
sub r1, r1, #(VCPU_USR_REG(3) - VCPU_USR_REG(0))
pop {r3, r4, r5}
- add sp, sp, #4 @ We loaded the VCPU pointer above
stmia r1, {r3, r4, r5}
sub r1, r1, #VCPU_USR_REG(0)
@@ -891,7 +895,7 @@ guest_trap:
@ inject an undefined exception to the guest.
#ifdef CONFIG_VFPv3
switch_to_guest_vfp:
- ldr r0, [sp, #12] @ Load VCPU pointer
+ load_vcpu r0 @ Load VCPU pointer
push {r3-r7}
@ NEON/VFP used. Turn on VFP access.
@@ -912,10 +916,11 @@ switch_to_guest_vfp:
.align
hyp_irq:
push {r0}
- ldr r0, [sp, #4] @ Load VCPU pointer
+ load_vcpu r0 @ Load VCPU pointer
add r0, r0, #(VCPU_USR_REG(1))
stmia r0, {r1-r12}
- pop {r0, r1} @ r1 == vcpu pointer
+ pop {r0}
+ load_vcpu r1 @ Load VCPU pointer again
str r0, [r1, #VCPU_USR_REG(0)]
mov r0, #ARM_EXCEPTION_IRQ
--
1.7.8.6
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