linux-kernel - [RFC PATCH 04/11] virt: sev-guest: Add simplified helper to assign vmpck

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Date:   Mon, 30 Jan 2023 17:33:20 +0530
From:   Nikunj A Dadhania <nikunj@....com>
To:     <linux-kernel@...r.kernel.org>, <x86@...nel.org>
CC:     <bp@...en8.de>, <thomas.lendacky@....com>,
        <dionnaglaze@...gle.com>, <pgonda@...gle.com>, <jroedel@...e.de>,
        <mingo@...hat.com>, <tglx@...utronix.de>,
        <dave.hansen@...ux.intel.com>, <seanjc@...gle.com>,
        <pbonzini@...hat.com>, <nikunj@....com>, <michael.roth@....com>,
        <ketanch@...k.ac.in>
Subject: [RFC PATCH 04/11] virt: sev-guest: Add simplified helper to assign vmpck

Simplify get_vmpck and prepare it to be used as an API. Update the
snp_guest_dev structure in snp_assign_vmpck(). Added vmpck_id to the
snp_guest_dev structure which can be used in SNP guest request API and
will remove direct use of vmpck_id command line parameter.

Signed-off-by: Nikunj A Dadhania <nikunj@....com>
---
 drivers/virt/coco/sev-guest/sev-guest.c | 41 ++++++++-----------------
 1 file changed, 12 insertions(+), 29 deletions(-)

diff --git a/drivers/virt/coco/sev-guest/sev-guest.c b/drivers/virt/coco/sev-guest/sev-guest.c
index af5b965c6c29..6eb2bd02a7c6 100644
--- a/drivers/virt/coco/sev-guest/sev-guest.c
+++ b/drivers/virt/coco/sev-guest/sev-guest.c
@@ -42,6 +42,7 @@ struct snp_guest_dev {
 	struct snp_req_data input;
 	u32 *os_area_msg_seqno;
 	u8 *vmpck;
+	u8 vmpck_id;
 };
 
 static u32 vmpck_id;
@@ -77,7 +78,7 @@ static inline unsigned int get_ctx_authsize(struct snp_guest_dev *snp_dev)
 static void snp_disable_vmpck(struct snp_guest_dev *snp_dev)
 {
 	dev_alert(snp_dev->dev, "Disabling vmpck_id %d to prevent IV reuse.\n",
-		  vmpck_id);
+		  snp_dev->vmpck_id);
 	memzero_explicit(snp_dev->vmpck, VMPCK_KEY_LEN);
 	snp_dev->vmpck = NULL;
 }
@@ -253,7 +254,7 @@ static int snp_send_guest_request(struct snp_guest_dev *snp_dev, struct snp_gues
 	memset(snp_dev->response, 0, sizeof(struct snp_guest_msg));
 
 	/* Encrypt the userspace provided payload */
-	rc = enc_payload(snp_dev, seqno, req, vmpck_id);
+	rc = enc_payload(snp_dev, seqno, req, snp_dev->vmpck_id);
 	if (rc)
 		return rc;
 
@@ -324,7 +325,6 @@ static int snp_send_guest_request(struct snp_guest_dev *snp_dev, struct snp_gues
 	return rc;
 }
 
-
 static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, u8 msg_version,
 				u8 msg_type, void *req_buf, size_t req_sz, void *resp_buf,
 				u32 resp_sz, __u64 *fw_err)
@@ -585,32 +585,16 @@ 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;
+	dev->vmpck = dev->layout->vmpck0 + vmpck_id * VMPCK_KEY_LEN;
+	dev->os_area_msg_seqno = &dev->layout->os_area.msg_seqno_0 + vmpck_id;
 
-	return key;
+	return true;
 }
 
 static int __init sev_guest_probe(struct platform_device *pdev)
@@ -639,8 +623,8 @@ 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;
 	}
@@ -654,7 +638,6 @@ 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));
-- 
2.32.0