linux-kernel - Re: [PATCH Part1 RFC v4 22/36] x86/sev: move MSR-based VMGEXITs for CPUID to helper

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Message-ID: <YR4oP+PDnmJbvfKR@zn.tnic>
Date:   Thu, 19 Aug 2021 11:45:35 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Brijesh Singh <brijesh.singh@....com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        linux-efi@...r.kernel.org, platform-driver-x86@...r.kernel.org,
        linux-coco@...ts.linux.dev, linux-mm@...ck.org,
        linux-crypto@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Joerg Roedel <jroedel@...e.de>,
        Tom Lendacky <thomas.lendacky@....com>,
        "H. Peter Anvin" <hpa@...or.com>, Ard Biesheuvel <ardb@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Sergio Lopez <slp@...hat.com>, Peter Gonda <pgonda@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        David Rientjes <rientjes@...gle.com>,
        Dov Murik <dovmurik@...ux.ibm.com>,
        Tobin Feldman-Fitzthum <tobin@....com>,
        Michael Roth <michael.roth@....com>,
        Vlastimil Babka <vbabka@...e.cz>, tony.luck@...el.com,
        brijesh.ksingh@...il.com
Subject: Re: [PATCH Part1 RFC v4 22/36] x86/sev: move MSR-based VMGEXITs for
 CPUID to helper

Finally drop this bouncing npmccallum at RH email address from the Cc
list.

On Wed, Jul 07, 2021 at 01:14:52PM -0500, Brijesh Singh wrote:
> From: Michael Roth <michael.roth@....com>
> 
> This code will also be used later for SEV-SNP-validated CPUID code in
> some cases, so move it to a common helper.
> 
> Signed-off-by: Michael Roth <michael.roth@....com>
> Signed-off-by: Brijesh Singh <brijesh.singh@....com>
> ---
>  arch/x86/kernel/sev-shared.c | 84 +++++++++++++++++++++++++-----------
>  1 file changed, 58 insertions(+), 26 deletions(-)
> 
> diff --git a/arch/x86/kernel/sev-shared.c b/arch/x86/kernel/sev-shared.c
> index be4025f14b4f..4884de256a49 100644
> --- a/arch/x86/kernel/sev-shared.c
> +++ b/arch/x86/kernel/sev-shared.c
> @@ -184,6 +184,58 @@ static enum es_result sev_es_ghcb_hv_call(struct ghcb *ghcb,
>  	return ret;
>  }
>  
> +static int sev_es_cpuid_msr_proto(u32 func, u32 subfunc, u32 *eax, u32 *ebx,

Since it is not only SEV-ES, then it should be prefixed with "sev_" like
we do for the other such functions. I guess simply

	sev_cpuid()

?

> +				  u32 *ecx, u32 *edx)
> +{
> +	u64 val;
> +
> +	if (eax) {

What's the protection for? Is it ever going to be called with NULL ptrs
for the regs? That's not the case in this patchset at least...

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette