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From:   Nikunj A Dadhania <nikunj@amd.com>
To:     <linux-kernel@vger.kernel.org>, <x86@kernel.org>
CC:     <bp@alien8.de>, <thomas.lendacky@amd.com>,
        <dionnaglaze@google.com>, <pgonda@google.com>, <seanjc@google.com>,
        <pbonzini@redhat.com>, <nikunj@amd.com>
Subject: [PATCH v3 05/14] virt: sev-guest: Add vmpck_id to snp_guest_dev struct
Date:   Sat, 22 Jul 2023 16:49:00 +0530
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Drop vmpck and os_area_msg_seqno pointers so that secret page layout
does not need to be exposed to the sev-guest driver after the rework.
Instead, add helper APIs to access vmpck and os_area_msg_seqno when
needed.

Signed-off-by: Nikunj A Dadhania <nikunj@amd.com>
---
 drivers/virt/coco/sev-guest/sev-guest.c | 84 +++++++++++++------------
 1 file changed, 43 insertions(+), 41 deletions(-)

diff --git a/drivers/virt/coco/sev-guest/sev-guest.c b/drivers/virt/coco/sev-guest/sev-guest.c
index d4241048b397..8ad43e007d3b 100644
--- a/drivers/virt/coco/sev-guest/sev-guest.c
+++ b/drivers/virt/coco/sev-guest/sev-guest.c
@@ -50,8 +50,7 @@ struct snp_guest_dev {
 
 	struct snp_secrets_page_layout *layout;
 	struct snp_req_data input;
-	u32 *os_area_msg_seqno;
-	u8 *vmpck;
+	unsigned int vmpck_id;
 };
 
 static u32 vmpck_id;
@@ -67,12 +66,23 @@ static inline unsigned int get_ctx_authsize(struct snp_guest_dev *snp_dev)
 	return 0;
 }
 
-static bool is_vmpck_empty(struct snp_guest_dev *snp_dev)
+static inline u8 *snp_get_vmpck(struct snp_guest_dev *snp_dev)
+{
+	return snp_dev->layout->vmpck0 + snp_dev->vmpck_id * VMPCK_KEY_LEN;
+}
+
+static inline u32 *snp_get_os_area_msg_seqno(struct snp_guest_dev *snp_dev)
+{
+	return &snp_dev->layout->os_area.msg_seqno_0 + snp_dev->vmpck_id;
+}
+
+static bool snp_is_vmpck_empty(struct snp_guest_dev *snp_dev)
 {
 	char zero_key[VMPCK_KEY_LEN] = {0};
+	u8 *key = snp_get_vmpck(snp_dev);
 
-	if (snp_dev->vmpck)
-		return !memcmp(snp_dev->vmpck, zero_key, VMPCK_KEY_LEN);
+	if (key)
+		return !memcmp(key, zero_key, VMPCK_KEY_LEN);
 
 	return true;
 }
@@ -96,20 +106,22 @@ static bool is_vmpck_empty(struct snp_guest_dev *snp_dev)
  */
 static void snp_disable_vmpck(struct snp_guest_dev *snp_dev)
 {
+	u8 *key = snp_get_vmpck(snp_dev);
+
 	dev_alert(snp_dev->dev, "Disabling vmpck_id %d to prevent IV reuse.\n",
-		  vmpck_id);
-	memzero_explicit(snp_dev->vmpck, VMPCK_KEY_LEN);
-	snp_dev->vmpck = NULL;
+		  snp_dev->vmpck_id);
+	memzero_explicit(key, VMPCK_KEY_LEN);
 }
 
 static inline u64 __snp_get_msg_seqno(struct snp_guest_dev *snp_dev)
 {
+	u32 *os_area_msg_seqno = snp_get_os_area_msg_seqno(snp_dev);
 	u64 count;
 
 	lockdep_assert_held(&snp_dev->cmd_mutex);
 
 	/* Read the current message sequence counter from secrets pages */
-	count = *snp_dev->os_area_msg_seqno;
+	count = *os_area_msg_seqno;
 
 	return count + 1;
 }
@@ -137,11 +149,13 @@ static u64 snp_get_msg_seqno(struct snp_guest_dev *snp_dev)
 
 static void snp_inc_msg_seqno(struct snp_guest_dev *snp_dev)
 {
+	u32 *os_area_msg_seqno = snp_get_os_area_msg_seqno(snp_dev);
+
 	/*
 	 * The counter is also incremented by the PSP, so increment it by 2
 	 * and save in secrets page.
 	 */
-	*snp_dev->os_area_msg_seqno += 2;
+	*os_area_msg_seqno += 2;
 }
 
 static inline struct snp_guest_dev *to_snp_dev(struct file *file)
@@ -151,15 +165,22 @@ static inline struct snp_guest_dev *to_snp_dev(struct file *file)
 	return container_of(dev, struct snp_guest_dev, misc);
 }
 
-static struct aesgcm_ctx *snp_init_crypto(u8 *key, size_t keylen)
+static struct aesgcm_ctx *snp_init_crypto(struct snp_guest_dev *snp_dev)
 {
 	struct aesgcm_ctx *ctx;
+	u8 *key;
+
+	if (snp_is_vmpck_empty(snp_dev)) {
+		pr_err("SNP: vmpck id %d is null\n", snp_dev->vmpck_id);
+		return NULL;
+	}
 
 	ctx = kzalloc(sizeof(*ctx), GFP_KERNEL_ACCOUNT);
 	if (!ctx)
 		return NULL;
 
-	if (aesgcm_expandkey(ctx, key, keylen, AUTHTAG_LEN)) {
+	key = snp_get_vmpck(snp_dev);
+	if (aesgcm_expandkey(ctx, key, VMPCK_KEY_LEN, AUTHTAG_LEN)) {
 		pr_err("SNP: crypto init failed\n");
 		kfree(ctx);
 		return NULL;
@@ -606,7 +627,7 @@ static long snp_guest_ioctl(struct file *file, unsigned int ioctl, unsigned long
 	mutex_lock(&snp_dev->cmd_mutex);
 
 	/* Check if the VMPCK is not empty */
-	if (is_vmpck_empty(snp_dev)) {
+	if (snp_is_vmpck_empty(snp_dev)) {
 		dev_err_ratelimited(snp_dev->dev, "VMPCK is disabled\n");
 		mutex_unlock(&snp_dev->cmd_mutex);
 		return -ENOTTY;
@@ -676,32 +697,14 @@ static const struct file_operations snp_guest_fops = {
 	.unlocked_ioctl = snp_guest_ioctl,
 };
 
-static u8 *get_vmpck(int id, struct snp_secrets_page_layout *layout, u32 **seqno)
+bool snp_assign_vmpck(struct snp_guest_dev *dev, int vmpck_id)
 {
-	u8 *key = NULL;
+	if (WARN_ON(vmpck_id > 3))
+		return false;
 
-	switch (id) {
-	case 0:
-		*seqno = &layout->os_area.msg_seqno_0;
-		key = layout->vmpck0;
-		break;
-	case 1:
-		*seqno = &layout->os_area.msg_seqno_1;
-		key = layout->vmpck1;
-		break;
-	case 2:
-		*seqno = &layout->os_area.msg_seqno_2;
-		key = layout->vmpck2;
-		break;
-	case 3:
-		*seqno = &layout->os_area.msg_seqno_3;
-		key = layout->vmpck3;
-		break;
-	default:
-		break;
-	}
+	dev->vmpck_id = vmpck_id;
 
-	return key;
+	return true;
 }
 
 static int __init sev_guest_probe(struct platform_device *pdev)
@@ -733,14 +736,14 @@ static int __init sev_guest_probe(struct platform_device *pdev)
 		goto e_unmap;
 
 	ret = -EINVAL;
-	snp_dev->vmpck = get_vmpck(vmpck_id, layout, &snp_dev->os_area_msg_seqno);
-	if (!snp_dev->vmpck) {
+	snp_dev->layout = layout;
+	if (!snp_assign_vmpck(snp_dev, vmpck_id)) {
 		dev_err(dev, "invalid vmpck id %d\n", vmpck_id);
 		goto e_unmap;
 	}
 
 	/* Verify that VMPCK is not zero. */
-	if (is_vmpck_empty(snp_dev)) {
+	if (snp_is_vmpck_empty(snp_dev)) {
 		dev_err(dev, "vmpck id %d is null\n", vmpck_id);
 		goto e_unmap;
 	}
@@ -748,7 +751,6 @@ static int __init sev_guest_probe(struct platform_device *pdev)
 	mutex_init(&snp_dev->cmd_mutex);
 	platform_set_drvdata(pdev, snp_dev);
 	snp_dev->dev = dev;
-	snp_dev->layout = layout;
 
 	/* Allocate the shared page used for the request and response message. */
 	snp_dev->request = alloc_shared_pages(dev, sizeof(struct snp_guest_msg));
@@ -764,7 +766,7 @@ static int __init sev_guest_probe(struct platform_device *pdev)
 		goto e_free_response;
 
 	ret = -EIO;
-	snp_dev->ctx = snp_init_crypto(snp_dev->vmpck, VMPCK_KEY_LEN);
+	snp_dev->ctx = snp_init_crypto(snp_dev);
 	if (!snp_dev->ctx)
 		goto e_free_cert_data;
 
-- 
2.34.1