KVM: VMX: Access @flags as a 32-bit value in __vmx_vcpu_run()

Access @flags using 32-bit operands when saving and testing @flags for
VMX_RUN_VMRESUME, as using 8-bit operands is unnecessarily fragile due
to relying on VMX_RUN_VMRESUME being in bits 0-7.  The behavior of
treating @flags a single byte is a holdover from when the param was
"bool launched", i.e. is not deliberate.

Cc: Alexey Dobriyan <adobriyan@gmail.com>
Reviewed-by: Jim Mattson <jmattson@google.com>
Link: https://lore.kernel.org/r/20221119003747.2615229-1-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

diff --git a/arch/x86/kvm/vmx/vmenter.S b/arch/x86/kvm/vmx/vmenter.S
index 766c6b3ef5ed95f5d4546cd4254aec8d275de2a7..cd2f75360bf37dba8a1cf5b84810af3eb52f49ac 100644 (file)
--- a/arch/x86/kvm/vmx/vmenter.S
+++ b/arch/x86/kvm/vmx/vmenter.S
@@ -69,8 +69,8 @@ SYM_FUNC_START(__vmx_vcpu_run)
         */
        push %_ASM_ARG2
 
-       /* Copy @flags to BL, _ASM_ARG3 is volatile. */
-       mov %_ASM_ARG3B, %bl
+       /* Copy @flags to EBX, _ASM_ARG3 is volatile. */
+       mov %_ASM_ARG3L, %ebx
 
        lea (%_ASM_SP), %_ASM_ARG2
        call vmx_update_host_rsp
@@ -106,7 +106,7 @@ SYM_FUNC_START(__vmx_vcpu_run)
        mov (%_ASM_SP), %_ASM_AX
 
        /* Check if vmlaunch or vmresume is needed */
-       testb $VMX_RUN_VMRESUME, %bl
+       test $VMX_RUN_VMRESUME, %ebx
 
        /* Load guest registers.  Don't clobber flags. */
        mov VCPU_RCX(%_ASM_AX), %_ASM_CX
@@ -128,7 +128,7 @@ SYM_FUNC_START(__vmx_vcpu_run)
        /* Load guest RAX.  This kills the @regs pointer! */
        mov VCPU_RAX(%_ASM_AX), %_ASM_AX
 
-       /* Check EFLAGS.ZF from 'testb' above */
+       /* Check EFLAGS.ZF from 'test VMX_RUN_VMRESUME' above */
        jz .Lvmlaunch
 
        /*