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Message-ID: <506a2e59-eea5-8c1e-ee1b-fbb7a401bd8d@linuxfoundation.org>
Date:   Thu, 12 May 2022 11:31:43 -0600
From:   Shuah Khan <skhan@...uxfoundation.org>
To:     Vishal Annapurve <vannapurve@...gle.com>, x86@...nel.org,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-kselftest@...r.kernel.org
Cc:     pbonzini@...hat.com, vkuznets@...hat.com, wanpengli@...cent.com,
        jmattson@...gle.com, joro@...tes.org, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com,
        hpa@...or.com, shauh@...nel.org, yang.zhong@...el.com,
        drjones@...hat.com, ricarkol@...gle.com, aaronlewis@...gle.com,
        wei.w.wang@...el.com, kirill.shutemov@...ux.intel.com,
        corbet@....net, hughd@...gle.com, jlayton@...nel.org,
        bfields@...ldses.org, akpm@...ux-foundation.org,
        chao.p.peng@...ux.intel.com, yu.c.zhang@...ux.intel.com,
        jun.nakajima@...el.com, dave.hansen@...el.com,
        michael.roth@....com, qperret@...gle.com, steven.price@....com,
        ak@...ux.intel.com, david@...hat.com, luto@...nel.org,
        vbabka@...e.cz, marcorr@...gle.com, erdemaktas@...gle.com,
        pgonda@...gle.com, nikunj@....com, seanjc@...gle.com,
        diviness@...gle.com, Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [RFC V2 PATCH 1/8] selftests: kvm: Fix inline assembly for
 hypercall

On 5/10/22 6:08 PM, Vishal Annapurve wrote:
> Fix inline assembly for hypercall to explicitly set
> eax with hypercall number to allow the implementation
> to work even in cases where compiler would inline the
> function.
> 

Please explain what happens without this change as well.

> Signed-off-by: Vishal Annapurve <vannapurve@...gle.com>
> ---
>   tools/testing/selftests/kvm/lib/x86_64/processor.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/kvm/lib/x86_64/processor.c b/tools/testing/selftests/kvm/lib/x86_64/processor.c
> index 9f000dfb5594..4d88e1a553bf 100644
> --- a/tools/testing/selftests/kvm/lib/x86_64/processor.c
> +++ b/tools/testing/selftests/kvm/lib/x86_64/processor.c
> @@ -1461,7 +1461,7 @@ uint64_t kvm_hypercall(uint64_t nr, uint64_t a0, uint64_t a1, uint64_t a2,
>   
>   	asm volatile("vmcall"
>   		     : "=a"(r)
> -		     : "b"(a0), "c"(a1), "d"(a2), "S"(a3));
> +		     : "a"(nr), "b"(a0), "c"(a1), "d"(a2), "S"(a3));
>   	return r;
>   }
>   
> 

With the above change to commit log:

Reviewed-by: Shuah Khan <skhan@...uxfoundation.org>

thanks,
-- Shuah

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