Re: [XEN PATCH 1/1] xen/x86: drop wrappers of SVM instructions

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 02/04/2025 3:54 pm, Alexander M. Merritt wrote:
> The new toolchain baseline knows the SVM instructions.
>
> Resolves: xen-project/xen#204
>
> Signed-off-by: Alexander M. Merritt <alexander@xxxxxxxxx>

Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, with a couple of
notes.

> ---
>  xen/arch/x86/hvm/svm/svm.h           | 14 +++-----------
>  xen/arch/x86/include/asm/asm-defns.h | 12 ------------
>  2 files changed, 3 insertions(+), 23 deletions(-)
>
> diff --git a/xen/arch/x86/hvm/svm/svm.h b/xen/arch/x86/hvm/svm/svm.h
> index beeaaab4f7..5c5e91a1ac 100644
> --- a/xen/arch/x86/hvm/svm/svm.h
> +++ b/xen/arch/x86/hvm/svm/svm.h
> @@ -23,25 +23,17 @@ void __update_guest_eip(struct cpu_user_regs *regs, 
> unsigned int inst_len);
>  
>  static inline void svm_vmload_pa(paddr_t vmcb)
>  {
> -    asm volatile (
> -        ".byte 0x0f,0x01,0xda" /* vmload */
> -        : : "a" (vmcb) : "memory" );
> +    asm volatile ( "vmload" : : "a" (vmcb) : "memory" );

We tend to prefer :: for empty sections.

>  }
>  
>  static inline void svm_vmsave_pa(paddr_t vmcb)
>  {
> -    asm volatile (
> -        ".byte 0x0f,0x01,0xdb" /* vmsave */
> -        : : "a" (vmcb) : "memory" );
> +    asm volatile ( "vmsave" : : "a" (vmcb) : "memory" );
>  }
>  
>  static inline void svm_invlpga(unsigned long linear, uint32_t asid)
>  {
> -    asm volatile (
> -        ".byte 0x0f,0x01,0xdf"
> -        : /* output */
> -        : /* input */
> -        "a" (linear), "c" (asid) );
> +    asm volatile ( "invlpga" : /* output */ : /* input */ "a" (linear), "c" 
> (asid) );

And here, the output/input comments are useless and can be dropped.

I can fix both on commit if you're happy?

~Andrew