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Message-ID: <484de126-872a-4b61-a30d-6baa73c9449c@amd.com>
Date: Wed, 4 Jun 2025 17:55:28 -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 v4 3/5] crypto: ccp: Add support to enable
CipherTextHiding on SNP_INIT_EX
On 6/3/2025 10:41 AM, Tom Lendacky wrote:
> On 5/19/25 18:57, Ashish Kalra wrote:
>> From: Ashish Kalra <ashish.kalra@....com>
>>
>> Ciphertext hiding needs to be enabled on SNP_INIT_EX.
>>
>> Add new argument to sev_platform_init_args to allow KVM module to
>> specify during SNP initialization if CipherTextHiding feature is
>> to be enabled and the maximum ASID usable for an SEV-SNP guest
>> when CipherTextHiding feature is enabled.
>>
>> Add new API interface to indicate if SEV-SNP CipherTextHiding
>> feature is supported by SEV firmware and additionally if
>> CipherTextHiding feature is enabled in the Platform BIOS.
>>
>> Signed-off-by: Ashish Kalra <ashish.kalra@....com>
>> ---
>> drivers/crypto/ccp/sev-dev.c | 30 +++++++++++++++++++++++++++---
>> include/linux/psp-sev.h | 15 +++++++++++++--
>> 2 files changed, 40 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
>> index b642f1183b8b..185668477182 100644
>> --- a/drivers/crypto/ccp/sev-dev.c
>> +++ b/drivers/crypto/ccp/sev-dev.c
>> @@ -1074,6 +1074,24 @@ static void snp_set_hsave_pa(void *arg)
>> wrmsrq(MSR_VM_HSAVE_PA, 0);
>> }
>>
>> +bool sev_is_snp_ciphertext_hiding_supported(void)
>> +{
>> + struct psp_device *psp = psp_master;
>> + struct sev_device *sev;
>> +
>> + sev = psp->sev_data;
>
> This needs a check for !psp and !psp->sev_data before de-referencing them.
>
Yes.
>> +
>> + /*
>> + * Feature information indicates if CipherTextHiding feature is
>> + * supported by the SEV firmware and additionally platform status
>> + * indicates if CipherTextHiding feature is enabled in the
>> + * Platform BIOS.
>> + */
>> + return ((sev->feat_info.ecx & SNP_CIPHER_TEXT_HIDING_SUPPORTED) &&
>> + sev->snp_plat_status.ciphertext_hiding_cap);
>
> Alignment.
>
Ok.
>> +}
>> +EXPORT_SYMBOL_GPL(sev_is_snp_ciphertext_hiding_supported);
>> +
>> static int snp_get_platform_data(struct sev_user_data_status *status, int *error)
>> {
>> struct sev_data_snp_feature_info snp_feat_info;
>> @@ -1167,7 +1185,7 @@ static int snp_filter_reserved_mem_regions(struct resource *rs, void *arg)
>> return 0;
>> }
>>
>> -static int __sev_snp_init_locked(int *error)
>> +static int __sev_snp_init_locked(int *error, unsigned int snp_max_snp_asid)
>
> s/snp_max_snp_asid/max_snp_asid/
>
Ok.
>> {
>> struct psp_device *psp = psp_master;
>> struct sev_data_snp_init_ex data;
>> @@ -1228,6 +1246,12 @@ static int __sev_snp_init_locked(int *error)
>> }
>>
>> memset(&data, 0, sizeof(data));
>> +
>> + if (snp_max_snp_asid) {
>> + data.ciphertext_hiding_en = 1;
>> + data.max_snp_asid = snp_max_snp_asid;
>> + }
>> +
>> data.init_rmp = 1;
>> data.list_paddr_en = 1;
>> data.list_paddr = __psp_pa(snp_range_list);
>> @@ -1412,7 +1436,7 @@ static int _sev_platform_init_locked(struct sev_platform_init_args *args)
>> if (sev->state == SEV_STATE_INIT)
>> return 0;
>>
>> - rc = __sev_snp_init_locked(&args->error);
>> + rc = __sev_snp_init_locked(&args->error, args->snp_max_snp_asid);
>> if (rc && rc != -ENODEV)
>> return rc;
>>
>> @@ -1495,7 +1519,7 @@ static int snp_move_to_init_state(struct sev_issue_cmd *argp, bool *shutdown_req
>> {
>> int error, rc;
>>
>> - rc = __sev_snp_init_locked(&error);
>> + rc = __sev_snp_init_locked(&error, 0);
>> if (rc) {
>> argp->error = SEV_RET_INVALID_PLATFORM_STATE;
>> return rc;
>> diff --git a/include/linux/psp-sev.h b/include/linux/psp-sev.h
>> index 0149d4a6aceb..66fecd0c0f88 100644
>> --- a/include/linux/psp-sev.h
>> +++ b/include/linux/psp-sev.h
>> @@ -746,10 +746,13 @@ struct sev_data_snp_guest_request {
>> struct sev_data_snp_init_ex {
>> u32 init_rmp:1;
>> u32 list_paddr_en:1;
>> - u32 rsvd:30;
>> + u32 rapl_dis:1;
>> + u32 ciphertext_hiding_en:1;
>> + u32 rsvd:28;
>> u32 rsvd1;
>> u64 list_paddr;
>> - u8 rsvd2[48];
>> + u16 max_snp_asid;
>> + u8 rsvd2[46];
>> } __packed;
>>
>> /**
>> @@ -798,10 +801,13 @@ struct sev_data_snp_shutdown_ex {
>> * @probe: True if this is being called as part of CCP module probe, which
>> * will defer SEV_INIT/SEV_INIT_EX firmware initialization until needed
>> * unless psp_init_on_probe module param is set
>> + * @snp_max_snp_asid: maximum ASID usable for SEV-SNP guest if
>
> Only a single space between the "*" and the "@"
>
> s/snp_max_snp_asid/max_snp_asid/
>
Ok.
Thanks,
Ashish
>> + * CipherTextHiding feature is to be enabled
>> */
>> struct sev_platform_init_args {
>> int error;
>> bool probe;
>> + unsigned int snp_max_snp_asid;
>
> s/snp_max_snp_asid/max_snp_asid/
>
> Thanks,
> Tom
>
>> };
>>
>> /**
>> @@ -841,6 +847,8 @@ struct snp_feature_info {
>> u32 edx;
>> } __packed;
>>
>> +#define SNP_CIPHER_TEXT_HIDING_SUPPORTED BIT(3)
>> +
>> #ifdef CONFIG_CRYPTO_DEV_SP_PSP
>>
>> /**
>> @@ -984,6 +992,7 @@ void *psp_copy_user_blob(u64 uaddr, u32 len);
>> void *snp_alloc_firmware_page(gfp_t mask);
>> void snp_free_firmware_page(void *addr);
>> void sev_platform_shutdown(void);
>> +bool sev_is_snp_ciphertext_hiding_supported(void);
>>
>> #else /* !CONFIG_CRYPTO_DEV_SP_PSP */
>>
>> @@ -1020,6 +1029,8 @@ static inline void snp_free_firmware_page(void *addr) { }
>>
>> static inline void sev_platform_shutdown(void) { }
>>
>> +static inline bool sev_is_snp_ciphertext_hiding_supported(void) { return false; }
>> +
>> #endif /* CONFIG_CRYPTO_DEV_SP_PSP */
>>
>> #endif /* __PSP_SEV_H__ */
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