2020-07-04 20:47:48

by David P. Reed

Subject: [PATCH v3 1/3] Correct asm VMXOFF side effects

Tell gcc that VMXOFF instruction clobbers condition codes
and memory when executed.
Also, correct original comments to remove kernel-doc syntax
per Randy Dunlap's request.

Suggested-by: Randy Dunlap <[email protected]>
Signed-off-by: David P. Reed <[email protected]>
---
arch/x86/include/asm/virtext.h | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/virtext.h b/arch/x86/include/asm/virtext.h
index 9aad0e0876fb..0ede8d04535a 100644
--- a/arch/x86/include/asm/virtext.h
+++ b/arch/x86/include/asm/virtext.h
@@ -30,7 +30,7 @@ static inline int cpu_has_vmx(void)
}


-/** Disable VMX on the current CPU
+/* Disable VMX on the current CPU
*
* vmxoff causes a undefined-opcode exception if vmxon was not run
* on the CPU previously. Only call this function if you know VMX
@@ -38,7 +38,7 @@ static inline int cpu_has_vmx(void)
*/
static inline void cpu_vmxoff(void)
{
- asm volatile ("vmxoff");
+ asm volatile ("vmxoff" ::: "cc", "memory");
cr4_clear_bits(X86_CR4_VMXE);
}

@@ -47,7 +47,7 @@ static inline int cpu_vmx_enabled(void)
return __read_cr4() & X86_CR4_VMXE;
}

-/** Disable VMX if it is enabled on the current CPU
+/* Disable VMX if it is enabled on the current CPU
*
* You shouldn't call this if cpu_has_vmx() returns 0.
*/
@@ -57,7 +57,7 @@ static inline void __cpu_emergency_vmxoff(void)
cpu_vmxoff();
}

-/** Disable VMX if it is supported and enabled on the current CPU
+/* Disable VMX if it is supported and enabled on the current CPU
*/
static inline void cpu_emergency_vmxoff(void)
{
--
2.26.2

2020-07-05 05:50:02

by Randy Dunlap

Subject: Re: [PATCH v3 1/3] Correct asm VMXOFF side effects

On 7/4/20 1:38 PM, David P. Reed wrote:
> Tell gcc that VMXOFF instruction clobbers condition codes
> and memory when executed.
> Also, correct original comments to remove kernel-doc syntax
> per Randy Dunlap's request.

Looks good. Thanks. For the comment changes:
Acked-by: Randy Dunlap <[email protected]>

> Suggested-by: Randy Dunlap <[email protected]>
> Signed-off-by: David P. Reed <[email protected]>
> ---
> arch/x86/include/asm/virtext.h | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/include/asm/virtext.h b/arch/x86/include/asm/virtext.h
> index 9aad0e0876fb..0ede8d04535a 100644
> --- a/arch/x86/include/asm/virtext.h
> +++ b/arch/x86/include/asm/virtext.h
> @@ -30,7 +30,7 @@ static inline int cpu_has_vmx(void)
> }
>
>
> -/** Disable VMX on the current CPU
> +/* Disable VMX on the current CPU
> *
> * vmxoff causes a undefined-opcode exception if vmxon was not run
> * on the CPU previously. Only call this function if you know VMX
> @@ -38,7 +38,7 @@ static inline int cpu_has_vmx(void)
> */
> static inline void cpu_vmxoff(void)
> {
> - asm volatile ("vmxoff");
> + asm volatile ("vmxoff" ::: "cc", "memory");
> cr4_clear_bits(X86_CR4_VMXE);
> }
>
> @@ -47,7 +47,7 @@ static inline int cpu_vmx_enabled(void)
> return __read_cr4() & X86_CR4_VMXE;
> }
>
> -/** Disable VMX if it is enabled on the current CPU
> +/* Disable VMX if it is enabled on the current CPU
> *
> * You shouldn't call this if cpu_has_vmx() returns 0.
> */
> @@ -57,7 +57,7 @@ static inline void __cpu_emergency_vmxoff(void)
> cpu_vmxoff();
> }
>
> -/** Disable VMX if it is supported and enabled on the current CPU
> +/* Disable VMX if it is supported and enabled on the current CPU
> */
> static inline void cpu_emergency_vmxoff(void)
> {
>


--
~Randy