From: Laurent Vivier <[email protected]>
This patch lets GCC to determine which registers to save when we
switch to/from a VCPU in the case of intel x86_64.
* Original code saves following registers:
rax, rbx, rcx, rdx, rsi, rdi, rbp,
r8, r9, r10, r11, r12, r13, r14, r15
* Patched code:
- informs GCC that we modify following registers
using the clobber description:
rbx, rdi, rsi,
r8, r9, r10, r11, r12, r13, r14, r15
- doesn't save rax because it is an output operand (vmx->fail)
- cannot put rcx in clobber description because it is an input operand,
but as we modify it and we want to keep its value (vcpu), we must
save it (pop/push)
- rbp is saved (pop/push) because GCC seems to ignore its use in the clobber
description.
- rdx is saved (pop/push) because it is reserved by GCC (REGPARM) and
cannot be put in the clobber description.
- line "mov (%%rsp), %3 \n\t" has been removed because %3
is rcx and rcx is restored just after.
- line ASM_VMX_VMWRITE_RSP_RDX() is moved out of the ifdef/else/endif
Signed-off-by: Laurent Vivier <[email protected]>
Signed-off-by: Avi Kivity <[email protected]>
---
drivers/kvm/vmx.c | 21 +++++++++------------
1 files changed, 9 insertions(+), 12 deletions(-)
diff --git a/drivers/kvm/vmx.c b/drivers/kvm/vmx.c
index 50c151e..3a58a2a 100644
--- a/drivers/kvm/vmx.c
+++ b/drivers/kvm/vmx.c
@@ -2265,16 +2265,12 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
asm(
/* Store host registers */
#ifdef CONFIG_X86_64
- "push %%rax; push %%rbx; push %%rdx;"
- "push %%rsi; push %%rdi; push %%rbp;"
- "push %%r8; push %%r9; push %%r10; push %%r11;"
- "push %%r12; push %%r13; push %%r14; push %%r15;"
+ "push %%rdx; push %%rbp;"
"push %%rcx \n\t"
- ASM_VMX_VMWRITE_RSP_RDX "\n\t"
#else
"pusha; push %%ecx \n\t"
- ASM_VMX_VMWRITE_RSP_RDX "\n\t"
#endif
+ ASM_VMX_VMWRITE_RSP_RDX "\n\t"
/* Check if vmlaunch of vmresume is needed */
"cmp $0, %1 \n\t"
/* Load guest registers. Don't clobber flags. */
@@ -2333,12 +2329,8 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
"mov %%r15, %c[r15](%3) \n\t"
"mov %%cr2, %%rax \n\t"
"mov %%rax, %c[cr2](%3) \n\t"
- "mov (%%rsp), %3 \n\t"
- "pop %%rcx; pop %%r15; pop %%r14; pop %%r13; pop %%r12;"
- "pop %%r11; pop %%r10; pop %%r9; pop %%r8;"
- "pop %%rbp; pop %%rdi; pop %%rsi;"
- "pop %%rdx; pop %%rbx; pop %%rax \n\t"
+ "pop %%rcx; pop %%rbp; pop %%rdx \n\t"
#else
"xchg %3, (%%esp) \n\t"
"mov %%eax, %c[rax](%3) \n\t"
@@ -2376,7 +2368,12 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
[r15]"i"(offsetof(struct kvm_vcpu, regs[VCPU_REGS_R15])),
#endif
[cr2]"i"(offsetof(struct kvm_vcpu, cr2))
- : "cc", "memory");
+ : "cc", "memory"
+#ifdef CONFIG_X86_64
+ , "rbx", "rdi", "rsi"
+ , "r8", "r9", "r10", "r11", "r12", "r13", "r14", "r15"
+#endif
+ );
vcpu->interrupt_window_open =
(vmcs_read32(GUEST_INTERRUPTIBILITY_INFO) & 3) == 0;
--
1.5.3.7
--
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