Nit (because I really suck at case-insensitive searches), please capitalize
"KVM: VMX:" in the shortlog.
On Fri, Nov 18, 2022, Alexey Dobriyan wrote:
> __vmx_vcpu_run_flags() returns "unsigned int" and uses only 2 bits of it
> so using "unsigned long" is very much pointless.
And __vmx_vcpu_run() and vmx_spec_ctrl_restore_host() take an "unsigned int" as
well, i.e. actually relying on an "unsigned long" value won't actually work.
On a related topic, this code in __vmx_vcpu_run() is unnecessarily fragile as it
relies on VMX_RUN_VMRESUME being in bits 0-7.
/* Copy @flags to BL, _ASM_ARG3 is volatile. */
mov %_ASM_ARG3, %bl
...
/* Check if vmlaunch or vmresume is needed */
testb $VMX_RUN_VMRESUME, %bl
The "byte" logic is another holdover, from when "flags" was just "launched" and
was passed in as a boolean. I'll send a proper patch to do:
diff --git a/arch/x86/kvm/vmx/vmenter.S b/arch/x86/kvm/vmx/vmenter.S
index 0b5db4de4d09..5bd39f63497d 100644
--- 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
/*
> Signed-off-by: Alexey Dobriyan <adobriyan@xxxxxxxxx>
> ---
Reviewed-by: Sean Christopherson <seanjc@xxxxxxxxxx>
