linux-kernel - Re: [PATCH RFC v8 45/56] KVM: SVM: Provide support for SNP_GUEST

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Date:   Fri, 24 Feb 2023 12:01:38 +0100
From:   Alexander Graf <graf@...zon.com>
To:     Michael Roth <michael.roth@....com>, <kvm@...r.kernel.org>
CC:     <linux-coco@...ts.linux.dev>, <linux-mm@...ck.org>,
        <linux-crypto@...r.kernel.org>, <x86@...nel.org>,
        <linux-kernel@...r.kernel.org>, <tglx@...utronix.de>,
        <mingo@...hat.com>, <jroedel@...e.de>, <thomas.lendacky@....com>,
        <hpa@...or.com>, <ardb@...nel.org>, <pbonzini@...hat.com>,
        <seanjc@...gle.com>, <vkuznets@...hat.com>, <jmattson@...gle.com>,
        <luto@...nel.org>, <dave.hansen@...ux.intel.com>, <slp@...hat.com>,
        <pgonda@...gle.com>, <peterz@...radead.org>,
        <srinivas.pandruvada@...ux.intel.com>, <rientjes@...gle.com>,
        <dovmurik@...ux.ibm.com>, <tobin@....com>, <bp@...en8.de>,
        <vbabka@...e.cz>, <kirill@...temov.name>, <ak@...ux.intel.com>,
        <tony.luck@...el.com>, <marcorr@...gle.com>,
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        <alpergun@...gle.com>, <dgilbert@...hat.com>, <jarkko@...nel.org>,
        <ashish.kalra@....com>, <nikunj.dadhania@....com>,
        Brijesh Singh <brijesh.singh@....com>
Subject: Re: [PATCH RFC v8 45/56] KVM: SVM: Provide support for
 SNP_GUEST_REQUEST NAE event


On 20.02.23 19:38, Michael Roth wrote:
> From: Brijesh Singh <brijesh.singh@....com>
>
> Version 2 of GHCB specification added the support for two SNP Guest
> Request Message NAE events. The events allows for an SEV-SNP guest to
> make request to the SEV-SNP firmware through hypervisor using the
> SNP_GUEST_REQUEST API define in the SEV-SNP firmware specification.
>
> The SNP_EXT_GUEST_REQUEST is similar to SNP_GUEST_REQUEST with the
> difference of an additional certificate blob that can be passed through
> the SNP_SET_CONFIG ioctl defined in the CCP driver. The CCP driver
> provides snp_guest_ext_guest_request() that is used by the KVM to get
> both the report and certificate data at once.
>
> Signed-off-by: Brijesh Singh <brijesh.singh@....com>
> Signed-off-by: Ashish Kalra <ashish.kalra@....com>
> Signed-off-by: Michael Roth <michael.roth@....com>
> ---
>   arch/x86/kvm/svm/sev.c | 185 +++++++++++++++++++++++++++++++++++++++--
>   arch/x86/kvm/svm/svm.h |   2 +
>   2 files changed, 181 insertions(+), 6 deletions(-)
>
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index 197b1f904567..92179614102e 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -327,6 +327,7 @@ static int sev_guest_init(struct kvm *kvm, struct kvm_sev_cmd *argp)
>                  if (ret)
>                          goto e_free;
>
> +               mutex_init(&sev->guest_req_lock);
>                  ret = sev_snp_init(&argp->error, false);
>          } else {
>                  ret = sev_platform_init(&argp->error);
> @@ -2059,23 +2060,34 @@ int sev_vm_move_enc_context_from(struct kvm *kvm, unsigned int source_fd)
>    */
>   static void *snp_context_create(struct kvm *kvm, struct kvm_sev_cmd *argp)
>   {
> +       struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
>          struct sev_data_snp_addr data = {};
> -       void *context;
> +       void *context, *certs_data;
>          int rc;
>
> +       /* Allocate memory used for the certs data in SNP guest request */
> +       certs_data = kzalloc(SEV_FW_BLOB_MAX_SIZE, GFP_KERNEL_ACCOUNT);
> +       if (!certs_data)
> +               return NULL;


I don't understand why this is part of the context creation, which again 
is part of the KVM_SEV_SNP_LAUNCH_START op. Would you mind to create a 
separate op for this and then check later on while you use the buffer 
whether it was ever allocated?


Alex





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