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Message-ID: <c80e8b87-cd39-4d6f-a170-19e66d83c273@amd.com>
Date: Wed, 2 Oct 2024 16:40:37 -0500
From: "Kalra, Ashish" <ashish.kalra@....com>
To: Tom Lendacky <thomas.lendacky@....com>, seanjc@...gle.com,
pbonzini@...hat.com, tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
dave.hansen@...ux.intel.com, hpa@...or.com, herbert@...dor.apana.org.au
Cc: x86@...nel.org, john.allen@....com, davem@...emloft.net,
michael.roth@....com, kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-crypto@...r.kernel.org
Subject: Re: [PATCH v2 2/3] crypto: ccp: Add support for SNP_FEATURE_INFO
command
Hello Tom,
On 10/2/2024 4:19 PM, Tom Lendacky wrote:
> On 10/2/24 16:18, Tom Lendacky wrote:
>> On 9/17/24 15:16, Ashish Kalra wrote:
>>> From: Ashish Kalra <ashish.kalra@....com>
>>>
>>> The FEATURE_INFO command provides host and guests a programmatic means
>>> to learn about the supported features of the currently loaded firmware.
>>> FEATURE_INFO command leverages the same mechanism as the CPUID instruction.
>>> Instead of using the CPUID instruction to retrieve Fn8000_0024,
>>> software can use FEATURE_INFO.
>>>
>>> Host/Hypervisor would use the FEATURE_INFO command, while guests would
>>> actually issue the CPUID instruction.
>>>
>>> The hypervisor can provide Fn8000_0024 values to the guest via the CPUID
>>> page in SNP_LAUNCH_UPDATE. As with all CPUID output recorded in that page,
>>> the hypervisor can filter Fn8000_0024. The firmware will examine
>>> Fn8000_0024 and apply its CPUID policy.
>>>
>>> During CCP module initialization, after firmware update, the SNP
>>> platform status and feature information from CPUID 0x8000_0024,
>>> sub-function 0, are cached in the sev_device structure.
>>>
>>> Signed-off-by: Ashish Kalra <ashish.kalra@....com>
>>> ---
>>> drivers/crypto/ccp/sev-dev.c | 47 ++++++++++++++++++++++++++++++++++++
>>> drivers/crypto/ccp/sev-dev.h | 3 +++
>>> include/linux/psp-sev.h | 29 ++++++++++++++++++++++
>>> 3 files changed, 79 insertions(+)
>>>
>>> diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
>>> index af018afd9cd7..564daf748293 100644
>>> --- a/drivers/crypto/ccp/sev-dev.c
>>> +++ b/drivers/crypto/ccp/sev-dev.c
>>> @@ -223,6 +223,7 @@ static int sev_cmd_buffer_len(int cmd)
>>> case SEV_CMD_SNP_GUEST_REQUEST: return sizeof(struct sev_data_snp_guest_request);
>>> case SEV_CMD_SNP_CONFIG: return sizeof(struct sev_user_data_snp_config);
>>> case SEV_CMD_SNP_COMMIT: return sizeof(struct sev_data_snp_commit);
>>> + case SEV_CMD_SNP_FEATURE_INFO: return sizeof(struct snp_feature_info);
>>> default: return 0;
>>> }
>>>
>>> @@ -1063,6 +1064,50 @@ static void snp_set_hsave_pa(void *arg)
>>> wrmsrl(MSR_VM_HSAVE_PA, 0);
>>> }
>>>
>>> +static void snp_get_platform_data(void)
>>> +{
>>> + struct sev_device *sev = psp_master->sev_data;
>>> + struct sev_data_snp_feature_info snp_feat_info;
>>> + struct snp_feature_info *feat_info;
>>> + struct sev_data_snp_addr buf;
>>> + int error = 0, rc;
>>> +
>>> + if (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))
>>> + return;
>>> +
>>> + /*
>>> + * The output buffer must be firmware page if SEV-SNP is
>>> + * initialized.
>> This comment is a little confusing relative to the "if" check that is
>> performed. Add some more detail about what this check is for.
>>
>> But... would this ever need to be called after SNP_INIT? Would we want
>> to call this again after, say, a DOWNLOAD_FIRMWARE command?
> Although, as I hit send I realized that we only do DOWNLOAD_FIRMWARE
> before SNP is initialized (currently).
We do have DOWNLOAD_FIRMWARE_EX support coming up which can/will happen after SNP_INIT, but there we can still use SEV's PLATFORM_DATA command to get (updated) SEV/SNP firmware version.
Thanks, Ashish
>
> Thanks,
> Tom
>
>> Thanks,
>> Tom
>>
>>> + */
>>> + if (sev->snp_initialized)
>>> + return;
>>> +
>>> + buf.address = __psp_pa(&sev->snp_plat_status);
>>> + rc = __sev_do_cmd_locked(SEV_CMD_SNP_PLATFORM_STATUS, &buf, &error);
>>> +
>>> + /*
>>> + * Do feature discovery of the currently loaded firmware,
>>> + * and cache feature information from CPUID 0x8000_0024,
>>> + * sub-function 0.
>>> + */
>>> + if (!rc && sev->snp_plat_status.feature_info) {
>>> + /*
>>> + * Use dynamically allocated structure for the SNP_FEATURE_INFO
>>> + * command to handle any alignment and page boundary check
>>> + * requirements.
>>> + */
>>> + feat_info = kzalloc(sizeof(*feat_info), GFP_KERNEL);
>>> + snp_feat_info.length = sizeof(snp_feat_info);
>>> + snp_feat_info.ecx_in = 0;
>>> + snp_feat_info.feature_info_paddr = __psp_pa(feat_info);
>>> +
>>> + rc = __sev_do_cmd_locked(SEV_CMD_SNP_FEATURE_INFO, &snp_feat_info, &error);
>>> + if (!rc)
>>> + sev->feat_info = *feat_info;
>>> + kfree(feat_info);
>>> + }
>>> +}
>>> +
>>> static int snp_filter_reserved_mem_regions(struct resource *rs, void *arg)
>>> {
>>> struct sev_data_range_list *range_list = arg;
>>> @@ -2415,6 +2460,8 @@ void sev_pci_init(void)
>>> api_major, api_minor, build,
>>> sev->api_major, sev->api_minor, sev->build);
>>>
>>> + snp_get_platform_data();
>>> +
>>> /* Initialize the platform */
>>> args.probe = true;
>>> rc = sev_platform_init(&args);
>>> diff --git a/drivers/crypto/ccp/sev-dev.h b/drivers/crypto/ccp/sev-dev.h
>>> index 3e4e5574e88a..1c1a51e52d2b 100644
>>> --- a/drivers/crypto/ccp/sev-dev.h
>>> +++ b/drivers/crypto/ccp/sev-dev.h
>>> @@ -57,6 +57,9 @@ struct sev_device {
>>> bool cmd_buf_backup_active;
>>>
>>> bool snp_initialized;
>>> +
>>> + struct sev_user_data_snp_status snp_plat_status;
>>> + struct snp_feature_info feat_info;
>>> };
>>>
>>> int sev_dev_init(struct psp_device *psp);
>>> diff --git a/include/linux/psp-sev.h b/include/linux/psp-sev.h
>>> index 903ddfea8585..6068a89839e1 100644
>>> --- a/include/linux/psp-sev.h
>>> +++ b/include/linux/psp-sev.h
>>> @@ -107,6 +107,7 @@ enum sev_cmd {
>>> SEV_CMD_SNP_DOWNLOAD_FIRMWARE_EX = 0x0CA,
>>> SEV_CMD_SNP_COMMIT = 0x0CB,
>>> SEV_CMD_SNP_VLEK_LOAD = 0x0CD,
>>> + SEV_CMD_SNP_FEATURE_INFO = 0x0CE,
>>>
>>> SEV_CMD_MAX,
>>> };
>>> @@ -812,6 +813,34 @@ struct sev_data_snp_commit {
>>> u32 len;
>>> } __packed;
>>>
>>> +/**
>>> + * struct sev_data_snp_feature_info - SEV_SNP_FEATURE_INFO structure
>>> + *
>>> + * @length: len of the command buffer read by the PSP
>>> + * @ecx_in: subfunction index
>>> + * @feature_info_paddr : SPA of the FEATURE_INFO structure
>>> + */
>>> +struct sev_data_snp_feature_info {
>>> + u32 length;
>>> + u32 ecx_in;
>>> + u64 feature_info_paddr;
>>> +} __packed;
>>> +
>>> +/**
>>> + * struct feature_info - FEATURE_INFO structure
>>> + *
>>> + * @eax: output of SNP_FEATURE_INFO command
>>> + * @ebx: output of SNP_FEATURE_INFO command
>>> + * @ecx: output of SNP_FEATURE_INFO command
>>> + * #edx: output of SNP_FEATURE_INFO command
>>> + */
>>> +struct snp_feature_info {
>>> + u32 eax;
>>> + u32 ebx;
>>> + u32 ecx;
>>> + u32 edx;
>>> +} __packed;
>>> +
>>> #ifdef CONFIG_CRYPTO_DEV_SP_PSP
>>>
>>> /**
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