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KVM: VMX: Let the compiler save/load RDX during vCPU-run

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Per commit c20363006a ("KVM: VMX: Let gcc to choose which registers
to save (x86_64)"), the only reason RDX is saved/loaded to/from the
stack is because it was specified as an input, i.e. couldn't be marked
as clobbered (ignoring the fact that "saving" it to a dummy output
would indirectly mark it as clobbered).

Now that RDX is no longer an input, clobber it.

Reviewed-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2019-01-25 07:40:54 -08:00 committed by Paolo Bonzini
parent ccf447434e
commit 6f7c6d23b7
1 changed files with 4 additions and 4 deletions
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8
arch/x86/kvm/vmx/vmx.c
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@ -6377,7 +6377,7 @@ static void __vmx_vcpu_run(struct kvm_vcpu *vcpu, struct vcpu_vmx *vmx)
asm(
/* Store host registers */
"push %%" _ASM_DX "; push %%" _ASM_BP ";"
"push %%" _ASM_BP " \n\t"
"sub $%c[wordsize], %%" _ASM_SP "\n\t" /* placeholder for guest RCX */
"push %%" _ASM_CX " \n\t"
"sub $%c[wordsize], %%" _ASM_SP "\n\t" /* temporarily adjust RSP for CALL */
@ -6481,7 +6481,7 @@ static void __vmx_vcpu_run(struct kvm_vcpu *vcpu, struct vcpu_vmx *vmx)
"xor %%esi, %%esi \n\t"
"xor %%edi, %%edi \n\t"
"xor %%ebp, %%ebp \n\t"
"pop %%" _ASM_BP "; pop %%" _ASM_DX " \n\t"
"pop %%" _ASM_BP " \n\t"
: ASM_CALL_CONSTRAINT, "=S"((int){0})
: "c"(vmx), "S"(evmcs_rsp),
[launched]"i"(offsetof(struct vcpu_vmx, __launched)),
@ -6509,10 +6509,10 @@ static void __vmx_vcpu_run(struct kvm_vcpu *vcpu, struct vcpu_vmx *vmx)
[wordsize]"i"(sizeof(ulong))
: "cc", "memory"
#ifdef CONFIG_X86_64
, "rax", "rbx", "rdi"
, "rax", "rbx", "rdx", "rdi"
, "r8", "r9", "r10", "r11", "r12", "r13", "r14", "r15"
#else
, "eax", "ebx", "edi"
, "eax", "ebx", "edx", "edi"
#endif
);
}