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Subject: Re: [PATCH v6 40/42] virt: Add SEV-SNP guest driver
To:     Brijesh Singh <brijesh.singh@amd.com>, x86@kernel.org,
        linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
        linux-efi@vger.kernel.org, platform-driver-x86@vger.kernel.org,
        linux-coco@lists.linux.dev, linux-mm@kvack.org
Cc:     Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Joerg Roedel <jroedel@suse.de>,
        Tom Lendacky <thomas.lendacky@amd.com>,
        "H. Peter Anvin" <hpa@zytor.com>, Ard Biesheuvel <ardb@kernel.org>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Sean Christopherson <seanjc@google.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Jim Mattson <jmattson@google.com>,
        Andy Lutomirski <luto@kernel.org>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Sergio Lopez <slp@redhat.com>, Peter Gonda <pgonda@google.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
        David Rientjes <rientjes@google.com>,
        Tobin Feldman-Fitzthum <tobin@ibm.com>,
        Borislav Petkov <bp@alien8.de>,
        Michael Roth <michael.roth@amd.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        "Kirill A . Shutemov" <kirill@shutemov.name>,
        Andi Kleen <ak@linux.intel.com>,
        "Dr . David Alan Gilbert" <dgilbert@redhat.com>,
        tony.luck@intel.com, marcorr@google.com,
        sathyanarayanan.kuppuswamy@linux.intel.com,
        Dov Murik <dovmurik@linux.ibm.com>
References: <20211008180453.462291-1-brijesh.singh@amd.com>
 <20211008180453.462291-41-brijesh.singh@amd.com>
From:   Dov Murik <dovmurik@linux.ibm.com>
Message-ID: <b79cfdfa-6482-70ab-3520-f76387fe4c27@linux.ibm.com>
Date:   Sun, 10 Oct 2021 20:51:17 +0300
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Hi Brijesh,

On 08/10/2021 21:04, Brijesh Singh wrote:
> SEV-SNP specification provides the guest a mechanisum to communicate with
> the PSP without risk from a malicious hypervisor who wishes to read, alter,
> drop or replay the messages sent. The driver uses snp_issue_guest_request()
> to issue GHCB SNP_GUEST_REQUEST or SNP_EXT_GUEST_REQUEST NAE events to
> submit the request to PSP.
> 
> The PSP requires that all communication should be encrypted using key
> specified through the platform_data.
> 
> The userspace can use SNP_GET_REPORT ioctl() to query the guest
> attestation report.
> 
> See SEV-SNP spec section Guest Messages for more details.
> 
> Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
> ---
>  Documentation/virt/coco/sevguest.rst  |  77 ++++
>  drivers/virt/Kconfig                  |   3 +
>  drivers/virt/Makefile                 |   1 +
>  drivers/virt/coco/sevguest/Kconfig    |   9 +
>  drivers/virt/coco/sevguest/Makefile   |   2 +
>  drivers/virt/coco/sevguest/sevguest.c | 561 ++++++++++++++++++++++++++
>  drivers/virt/coco/sevguest/sevguest.h |  98 +++++
>  include/uapi/linux/sev-guest.h        |  44 ++
>  8 files changed, 795 insertions(+)
>  create mode 100644 Documentation/virt/coco/sevguest.rst
>  create mode 100644 drivers/virt/coco/sevguest/Kconfig
>  create mode 100644 drivers/virt/coco/sevguest/Makefile
>  create mode 100644 drivers/virt/coco/sevguest/sevguest.c
>  create mode 100644 drivers/virt/coco/sevguest/sevguest.h
>  create mode 100644 include/uapi/linux/sev-guest.h
> 

[...]


> +
> +static u8 *get_vmpck(int id, struct snp_secrets_page_layout *layout, u32 **seqno)
> +{
> +	u8 *key = NULL;
> +
> +	switch (id) {
> +	case 0:
> +		*seqno = &layout->os_area.msg_seqno_0;
> +		key = layout->vmpck0;
> +		break;
> +	case 1:
> +		*seqno = &layout->os_area.msg_seqno_1;
> +		key = layout->vmpck1;
> +		break;
> +	case 2:
> +		*seqno = &layout->os_area.msg_seqno_2;
> +		key = layout->vmpck2;
> +		break;
> +	case 3:
> +		*seqno = &layout->os_area.msg_seqno_3;
> +		key = layout->vmpck3;
> +		break;
> +	default:
> +		break;
> +	}
> +
> +	return NULL;

This should be 'return key', right?

-Dov

> +}
> +