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Message-ID: <3b2e58da-33da-1b40-2599-e7992e1674c7@amd.com>
Date: Wed, 2 Oct 2024 16:18:00 -0500
From: Tom Lendacky <thomas.lendacky@....com>
To: Ashish Kalra <Ashish.Kalra@....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
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?
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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