Per commit c20363006af6 ("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, mark it as clobbered and zero it
out to prevent speculative use.
Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
---
arch/x86/kvm/vmx/vmx.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index f0084726d0c3..b509e22dbcbe 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -6376,7 +6376,7 @@ 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 */
@@ -6470,9 +6470,10 @@ static void __vmx_vcpu_run(struct kvm_vcpu *vcpu, struct vcpu_vmx *vmx)
"xor %%eax, %%eax \n\t"
"xor %%ebx, %%ebx \n\t"
+ "xor %%edx, %%edx \n\t"
"xor %%esi, %%esi \n\t"
"xor %%edi, %%edi \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)),
@@ -6500,10 +6501,10 @@ 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
);
}
--
2.20.1
