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Commit 40712fae authored by Avi Kivity's avatar Avi Kivity Committed by Marcelo Tosatti
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KVM: VMX: Avoid atomic operation in vmx_vcpu_run 



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: default avatarAvi Kivity <avi@redhat.com>
Signed-off-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
parent 1c696d0e

arch/x86/kvm/vmx.c

+5 −2
Original line number Diff line number Diff line
@@ -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