linux-kernel - [PATCH v7 5/7] crypto: ccp - Add support to enable CipherTextHiding on SNP_INIT

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Message-ID: <727d1afc55ac4292d611da71d661a4cfe55fd5cd.1752869333.git.ashish.kalra@amd.com>
Date: Mon, 21 Jul 2025 14:13:55 +0000
From: Ashish Kalra <Ashish.Kalra@....com>
To: <corbet@....net>, <seanjc@...gle.com>, <pbonzini@...hat.com>,
	<tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>,
	<dave.hansen@...ux.intel.com>, <x86@...nel.org>, <hpa@...or.com>,
	<thomas.lendacky@....com>, <john.allen@....com>,
	<herbert@...dor.apana.org.au>, <davem@...emloft.net>,
	<akpm@...ux-foundation.org>, <rostedt@...dmis.org>, <paulmck@...nel.org>
CC: <nikunj@....com>, <Neeraj.Upadhyay@....com>, <aik@....com>,
	<ardb@...nel.org>, <michael.roth@....com>, <arnd@...db.de>,
	<linux-doc@...r.kernel.org>, <linux-crypto@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <kvm@...r.kernel.org>
Subject: [PATCH v7 5/7] crypto: ccp - Add support to enable CipherTextHiding on SNP_INIT_EX

From: Ashish Kalra <ashish.kalra@....com>

To enable ciphertext hiding, it must be specified in the SNP_INIT_EX
command as part of SNP initialization.

Modify the sev_platform_init_args structure, which is used as input to
sev_platform_init(), to include a field that, when non-zero,
indicates that ciphertext hiding should be enabled and specifies the
maximum ASID that can be used for an SEV-SNP guest.

Reviewed-by: Tom Lendacky <thomas.lendacky@....com>
Signed-off-by: Ashish Kalra <ashish.kalra@....com>
---
 drivers/crypto/ccp/sev-dev.c | 12 +++++++++---
 include/linux/psp-sev.h      | 10 ++++++++--
 2 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
index 58c9e040e9ac..334405461657 100644
--- a/drivers/crypto/ccp/sev-dev.c
+++ b/drivers/crypto/ccp/sev-dev.c
@@ -1186,7 +1186,7 @@ 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 max_snp_asid)
 {
 	struct psp_device *psp = psp_master;
 	struct sev_data_snp_init_ex data;
@@ -1247,6 +1247,12 @@ static int __sev_snp_init_locked(int *error)
 		}
 
 		memset(&data, 0, sizeof(data));
+
+		if (max_snp_asid) {
+			data.ciphertext_hiding_en = 1;
+			data.max_snp_asid = max_snp_asid;
+		}
+
 		data.init_rmp = 1;
 		data.list_paddr_en = 1;
 		data.list_paddr = __psp_pa(snp_range_list);
@@ -1433,7 +1439,7 @@ static int _sev_platform_init_locked(struct sev_platform_init_args *args)
 	if (sev->sev_plat_status.state == SEV_STATE_INIT)
 		return 0;
 
-	rc = __sev_snp_init_locked(&args->error);
+	rc = __sev_snp_init_locked(&args->error, args->max_snp_asid);
 	if (rc && rc != -ENODEV)
 		return rc;
 
@@ -1516,7 +1522,7 @@ 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 d83185b4268b..e0dbcb4b4fd9 100644
--- a/include/linux/psp-sev.h
+++ b/include/linux/psp-sev.h
@@ -748,10 +748,13 @@ 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;
 
 /**
@@ -800,10 +803,13 @@ 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
+ * @max_snp_asid: When non-zero, enable ciphertext hiding and specify the
+ *  maximum ASID that can be used for an SEV-SNP guest.
  */
 struct sev_platform_init_args {
 	int error;
 	bool probe;
+	unsigned int max_snp_asid;
 };
 
 /**
-- 
2.34.1