Instead of exchanging the guest and host rcx, have separate storage
for each. This allows us to avoid using the xchg instruction, which
is is a little slower than normal operations.
Signed-off-by: Avi Kivity <a...@redhat.com>
---
arch/x86/kvm/vmx.c | 7 +++++--
1 files changed, 5 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 0d56fe0..d9fd4e6 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -3991,6 +3991,7 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu)
asm(
/* Store host registers */
"push %%"R"dx; push %%"R"bp;"
+ "push %%"R"cx \n\t" /* placeholder for guest rcx */
"push %%"R"cx \n\t"
"cmp %%"R"sp, %c[host_rsp](%0) \n\t"
"je 1f \n\t"
@@ -4032,7 +4033,8 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu)
".Llaunched: " __ex(ASM_VMX_VMRESUME) "\n\t"
".Lkvm_vmx_return: "
/* Save guest registers, load host registers, keep flags */
- "xchg %0, (%%"R"sp) \n\t"
+ "mov %0, %c[wordsize](%%"R"sp) \n\t"
+ "pop %0 \n\t"
"mov %%"R"ax, %c[rax](%0) \n\t"
"mov %%"R"bx, %c[rbx](%0) \n\t"
"pop"Q" %c[rcx](%0) \n\t"
@@ -4076,7 +4078,8 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu)
[r14]"i"(offsetof(struct vcpu_vmx,
vcpu.arch.regs[VCPU_REGS_R14])),
[r15]"i"(offsetof(struct vcpu_vmx,
vcpu.arch.regs[VCPU_REGS_R15])),
#endif
- [cr2]"i"(offsetof(struct vcpu_vmx, vcpu.arch.cr2))
+ [cr2]"i"(offsetof(struct vcpu_vmx, vcpu.arch.cr2)),
+ [wordsize]"i"(sizeof(ulong))
: "cc", "memory"
, R"ax", R"bx", R"di", R"si"
#ifdef CONFIG_X86_64
--
1.7.1
--
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