linux-kernel - Re: [PATCH Part2 v5 32/45] KVM: x86: Define RMP page fault error bits for #NPF

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Date:   Thu, 30 Sep 2021 16:41:54 -0700
From:   Marc Orr <marcorr@...gle.com>
To:     Brijesh Singh <brijesh.singh@....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@...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>,
        Borislav Petkov <bp@...en8.de>,
        Michael Roth <michael.roth@....com>,
        Vlastimil Babka <vbabka@...e.cz>,
        "Kirill A . Shutemov" <kirill@...temov.name>,
        Andi Kleen <ak@...ux.intel.com>, tony.luck@...el.com,
        sathyanarayanan.kuppuswamy@...ux.intel.com
Subject: Re: [PATCH Part2 v5 32/45] KVM: x86: Define RMP page fault error bits
 for #NPF

On Fri, Aug 20, 2021 at 9:00 AM Brijesh Singh <brijesh.singh@....com> wrote:
>
> When SEV-SNP is enabled globally, the hardware places restrictions on all
> memory accesses based on the RMP entry, whether the hypervisor or a VM,
> performs the accesses. When hardware encounters an RMP access violation
> during a guest access, it will cause a #VMEXIT(NPF).
>
> See APM2 section 16.36.10 for more details.

nit: Section # should be 15.36.10 (rather than 16.36.10). Also, is it
better to put section headings, rather than numbers in the commit logs
and comments? Someone mentioned to me that the section numbering in
APM and SDM can move around over time, but the section titles tend to
be more stable. I'm not sure how true this is, so feel free to
disregard this comment.

>
> Signed-off-by: Brijesh Singh <brijesh.singh@....com>
> ---
>  arch/x86/include/asm/kvm_host.h | 8 ++++++++
>  1 file changed, 8 insertions(+)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 109e80167f11..a6e764458f3e 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -239,8 +239,12 @@ enum x86_intercept_stage;
>  #define PFERR_FETCH_BIT 4
>  #define PFERR_PK_BIT 5
>  #define PFERR_SGX_BIT 15
> +#define PFERR_GUEST_RMP_BIT 31
>  #define PFERR_GUEST_FINAL_BIT 32
>  #define PFERR_GUEST_PAGE_BIT 33
> +#define PFERR_GUEST_ENC_BIT 34
> +#define PFERR_GUEST_SIZEM_BIT 35
> +#define PFERR_GUEST_VMPL_BIT 36
>
>  #define PFERR_PRESENT_MASK (1U << PFERR_PRESENT_BIT)
>  #define PFERR_WRITE_MASK (1U << PFERR_WRITE_BIT)
> @@ -251,6 +255,10 @@ enum x86_intercept_stage;
>  #define PFERR_SGX_MASK (1U << PFERR_SGX_BIT)
>  #define PFERR_GUEST_FINAL_MASK (1ULL << PFERR_GUEST_FINAL_BIT)
>  #define PFERR_GUEST_PAGE_MASK (1ULL << PFERR_GUEST_PAGE_BIT)
> +#define PFERR_GUEST_RMP_MASK (1ULL << PFERR_GUEST_RMP_BIT)
> +#define PFERR_GUEST_ENC_MASK (1ULL << PFERR_GUEST_ENC_BIT)
> +#define PFERR_GUEST_SIZEM_MASK (1ULL << PFERR_GUEST_SIZEM_BIT)
> +#define PFERR_GUEST_VMPL_MASK (1ULL << PFERR_GUEST_VMPL_BIT)
>
>  #define PFERR_NESTED_GUEST_PAGE (PFERR_GUEST_PAGE_MASK |       \
>                                  PFERR_WRITE_MASK |             \
> --
> 2.17.1
>