On 20/5/25 09:57, Ashish Kalra wrote:
From: Ashish Kalra <ashish.kalra@xxxxxxx>
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@xxxxxxx>
---
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;
+
+ /*
+ * 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);
+}
+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)
{
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
+ * CipherTextHiding feature is to be enabled
*/
struct sev_platform_init_args {
int error;
bool probe;
+ unsigned int snp_max_snp_asid;
};
/**
@@ -841,6 +847,8 @@ struct snp_feature_info {
u32 edx;
} __packed;
+#define SNP_CIPHER_TEXT_HIDING_SUPPORTED BIT(3)
SNP_FEATURE_CIPHER_TEXT_HIDING ?
or X86_FEATURE_CIPHER_TEXT_HIDING ?
In other words, mimic X86_FEATURE_SEV which is a real CPUID bit and FEATURE_INFO mimics CPUID. Thanks,
+
#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__ */
--
Alexey
