linux-kernel - Re: [PATCH Part2 v6 04/49] x86/sev: set SYSCFG.MFMD

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Date:   Thu, 23 Jun 2022 14:00:36 -0700
From:   Marc Orr <marcorr@...gle.com>
To:     Ashish Kalra <Ashish.Kalra@....com>
Cc:     x86 <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>,
        kvm list <kvm@...r.kernel.org>, linux-coco@...ts.linux.dev,
        linux-mm@...ck.org,
        Linux Crypto Mailing List <linux-crypto@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Joerg Roedel <jroedel@...e.de>,
        "Lendacky, Thomas" <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>,
        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>,
        Borislav Petkov <bp@...en8.de>,
        "Roth, Michael" <michael.roth@....com>,
        Vlastimil Babka <vbabka@...e.cz>,
        "Kirill A . Shutemov" <kirill@...temov.name>,
        Andi Kleen <ak@...ux.intel.com>,
        Tony Luck <tony.luck@...el.com>,
        Sathyanarayanan Kuppuswamy 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        Alper Gun <alpergun@...gle.com>,
        "Dr . David Alan Gilbert" <dgilbert@...hat.com>, jarkko@...nel.org
Subject: Re: [PATCH Part2 v6 04/49] x86/sev: set SYSCFG.MFMD

On Mon, Jun 20, 2022 at 4:02 PM Ashish Kalra <Ashish.Kalra@....com> wrote:
>
> From: Brijesh Singh <brijesh.singh@....com>
>
> SEV-SNP FW >= 1.51 requires that SYSCFG.MFMD must be set.
>
> Subsequent CCP patches while require 1.51 as the minimum SEV-SNP
> firmware version.
>
> Signed-off-by: Brijesh Singh <brijesh.singh@....com>
> ---
>  arch/x86/include/asm/msr-index.h |  3 +++
>  arch/x86/kernel/sev.c            | 24 ++++++++++++++++++++++++
>  2 files changed, 27 insertions(+)
>
> diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
> index 57a8280e283a..1e36f16daa56 100644
> --- a/arch/x86/include/asm/msr-index.h
> +++ b/arch/x86/include/asm/msr-index.h
> @@ -587,6 +587,9 @@
>  #define MSR_AMD64_SYSCFG_SNP_EN                BIT_ULL(MSR_AMD64_SYSCFG_SNP_EN_BIT)
>  #define MSR_AMD64_SYSCFG_SNP_VMPL_EN_BIT       25
>  #define MSR_AMD64_SYSCFG_SNP_VMPL_EN   BIT_ULL(MSR_AMD64_SYSCFG_SNP_VMPL_EN_BIT)
> +#define MSR_AMD64_SYSCFG_MFDM_BIT              19
> +#define MSR_AMD64_SYSCFG_MFDM          BIT_ULL(MSR_AMD64_SYSCFG_MFDM_BIT)

nit: Similar to the previous patch, the alignment here doesn't look
right. The bad alignment can be viewed on the github version of this
patch:
https://github.com/AMDESE/linux/commit/6d4469b86f90e67119ff110230857788a0d9dbd0

> +
>  #define MSR_K8_INT_PENDING_MSG         0xc0010055
>  /* C1E active bits in int pending message */
>  #define K8_INTP_C1E_ACTIVE_MASK                0x18000000
> diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
> index 3a233b5d47c5..25c7feb367f6 100644
> --- a/arch/x86/kernel/sev.c
> +++ b/arch/x86/kernel/sev.c
> @@ -2257,6 +2257,27 @@ static __init void snp_enable(void *arg)
>         __snp_enable(smp_processor_id());
>  }
>
> +static int __mfdm_enable(unsigned int cpu)
> +{
> +       u64 val;
> +
> +       if (!cpu_feature_enabled(X86_FEATURE_SEV_SNP))
> +               return 0;
> +
> +       rdmsrl(MSR_AMD64_SYSCFG, val);
> +
> +       val |= MSR_AMD64_SYSCFG_MFDM;

Can we do this inside `__snp_enable()`, above? Then, we'll execute if
a hotplug event happens as well.

static int __snp_enable(unsigned int cpu)
{
     u64 val;

     if (!cpu_feature_enabled(X86_FEATURE_SEV_SNP))
          return 0;

     rdmsrl(MSR_AMD64_SYSCFG, val);

     val |= MSR_AMD64_SYSCFG_SNP_EN;
     val |= MSR_AMD64_SYSCFG_SNP_VMPL_EN;
     val |= MSR_AMD64_SYSCFG_MFDM;

     wrmsrl(MSR_AMD64_SYSCFG, val);

     return 0;
}

> +
> +       wrmsrl(MSR_AMD64_SYSCFG, val);
> +
> +       return 0;
> +}
> +
> +static __init void mfdm_enable(void *arg)
> +{
> +       __mfdm_enable(smp_processor_id());
> +}
> +
>  static bool get_rmptable_info(u64 *start, u64 *len)
>  {
>         u64 calc_rmp_sz, rmp_sz, rmp_base, rmp_end, nr_pages;
> @@ -2325,6 +2346,9 @@ static __init int __snp_rmptable_init(void)
>         /* Flush the caches to ensure that data is written before SNP is enabled. */
>         wbinvd_on_all_cpus();
>
> +       /* MFDM must be enabled on all the CPUs prior to enabling SNP. */
> +       on_each_cpu(mfdm_enable, NULL, 1);
> +
>         /* Enable SNP on all CPUs. */
>         on_each_cpu(snp_enable, NULL, 1);
>
> --
> 2.25.1
>