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KVM: VMX: Avoid atomic operation in vmx_vcpu_run

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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 <avi@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
This commit is contained in:
Avi Kivity 2011-01-06 18:09:12 +02:00 committed by Marcelo Tosatti
parent 1c696d0e1b
commit 40712faeb8
1 changed files with 5 additions and 2 deletions
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7
arch/x86/kvm/vmx.c
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@ -4022,6 +4022,7 @@ 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"
@ -4063,7 +4064,8 @@ 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"
@ -4107,7 +4109,8 @@ 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