linux-kernel - Re: [PATCH Part2 v5 16/45] crypto: ccp: Add the SNP_PLATFORM

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Date:   Thu, 23 Sep 2021 13:01:47 -0500
From:   Brijesh Singh <brijesh.singh@....com>
To:     "Dr. David Alan Gilbert" <dgilbert@...hat.com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org, 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,
        marcorr@...gle.com, sathyanarayanan.kuppuswamy@...ux.intel.com
Subject: Re: [PATCH Part2 v5 16/45] crypto: ccp: Add the SNP_PLATFORM_STATUS
 command


On 9/22/21 12:35 PM, Dr. David Alan Gilbert wrote:
> * Brijesh Singh (brijesh.singh@....com) wrote:
>> The command can be used by the userspace to query the SNP platform status
>> report. See the SEV-SNP spec for more details.
>>
>> Signed-off-by: Brijesh Singh <brijesh.singh@....com>
>> ---
>>  Documentation/virt/coco/sevguest.rst | 27 +++++++++++++++++
>>  drivers/crypto/ccp/sev-dev.c         | 45 ++++++++++++++++++++++++++++
>>  include/uapi/linux/psp-sev.h         |  1 +
>>  3 files changed, 73 insertions(+)
>>
>> diff --git a/Documentation/virt/coco/sevguest.rst b/Documentation/virt/coco/sevguest.rst
>> index 7acb8696fca4..7c51da010039 100644
>> --- a/Documentation/virt/coco/sevguest.rst
>> +++ b/Documentation/virt/coco/sevguest.rst
>> @@ -52,6 +52,22 @@ to execute due to the firmware error, then fw_err code will be set.
>>                  __u64 fw_err;
>>          };
>>  
>> +The host ioctl should be called to /dev/sev device. The ioctl accepts command
>> +id and command input structure.
>> +
>> +::
>> +        struct sev_issue_cmd {
>> +                /* Command ID */
>> +                __u32 cmd;
>> +
>> +                /* Command request structure */
>> +                __u64 data;
>> +
>> +                /* firmware error code on failure (see psp-sev.h) */
>> +                __u32 error;
>> +        };
>> +
>> +
>>  2.1 SNP_GET_REPORT
>>  ------------------
>>  
>> @@ -107,3 +123,14 @@ length of the blob is lesser than expected then snp_ext_report_req.certs_len wil
>>  be updated with the expected value.
>>  
>>  See GHCB specification for further detail on how to parse the certificate blob.
>> +
>> +2.3 SNP_PLATFORM_STATUS
>> +-----------------------
>> +:Technology: sev-snp
>> +:Type: hypervisor ioctl cmd
>> +:Parameters (in): struct sev_data_snp_platform_status
>> +:Returns (out): 0 on success, -negative on error
>> +
>> +The SNP_PLATFORM_STATUS command is used to query the SNP platform status. The
>> +status includes API major, minor version and more. See the SEV-SNP
>> +specification for further details.
>> diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
>> index 4cd7d803a624..16c6df5d412c 100644
>> --- a/drivers/crypto/ccp/sev-dev.c
>> +++ b/drivers/crypto/ccp/sev-dev.c
>> @@ -1394,6 +1394,48 @@ static int sev_ioctl_do_pdh_export(struct sev_issue_cmd *argp, bool writable)
>>  	return ret;
>>  }
>>  
>> +static int sev_ioctl_snp_platform_status(struct sev_issue_cmd *argp)
>> +{
>> +	struct sev_device *sev = psp_master->sev_data;
>> +	struct sev_data_snp_platform_status_buf buf;
>> +	struct page *status_page;
>> +	void *data;
>> +	int ret;
>> +
>> +	if (!sev->snp_inited || !argp->data)
>> +		return -EINVAL;
>> +
>> +	status_page = alloc_page(GFP_KERNEL_ACCOUNT);
>> +	if (!status_page)
>> +		return -ENOMEM;
>> +
>> +	data = page_address(status_page);
>> +	if (snp_set_rmp_state(__pa(data), 1, true, true, false)) {
>> +		__free_pages(status_page, 0);
>> +		return -EFAULT;
>> +	}
>> +
>> +	buf.status_paddr = __psp_pa(data);
>> +	ret = __sev_do_cmd_locked(SEV_CMD_SNP_PLATFORM_STATUS, &buf, &argp->error);
>> +
>> +	/* Change the page state before accessing it */
>> +	if (snp_set_rmp_state(__pa(data), 1, false, true, true)) {
>> +		snp_leak_pages(__pa(data) >> PAGE_SHIFT, 1);
>> +		return -EFAULT;
>> +	}
> Could we find a way of returning some of these errors into the output,
> rather than interepreting them from errno values?

I can try to find a corresponding fw error code and use it where
applicable. e.g in this case I can use the SEV_RET_INVALID_PAGE_STATE.

thanks