[PATCH v6 05/16] virt: sev-guest: Add vmpck_id to snp_guest_dev struct

Nikunj A Dadhania
2023-11-28T13:01:17Z

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.

Also, change function is_vmpck_empty() to snp_is_vmpck_empty() in
preparation for moving to sev.c.

Signed-off-by: Nikunj A Dadhania <nikunj@amd.com>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
---
drivers/virt/coco/sev-guest/sev-guest.c | 95 ++++++++++++-------------
1 file changed, 47 insertions(+), 48 deletions(-)

diff --git a/drivers/virt/coco/sev-guest/sev-guest.c b/drivers/virt/coco/sev-guest/sev-guest.c
index 1579140d43ec..0f2134deca51 100644
--- a/drivers/virt/coco/sev-guest/sev-guest.c
+++ b/drivers/virt/coco/sev-guest/sev-guest.c
@@ -59,22 +59,29 @@ struct snp_guest_dev {
struct snp_derived_key_req derived_key;
struct snp_ext_report_req ext_report;
} req;
- u32 *os_area_msg_seqno;
- u8 *vmpck;
+ unsigned int vmpck_id;
};

static u32 vmpck_id;
module_param(vmpck_id, uint, 0444);
MODULE_PARM_DESC(vmpck_id, "The VMPCK ID to use when communicating with the PSP.");

-static bool is_vmpck_empty(struct snp_guest_dev *snp_dev)
+static inline u8 *snp_get_vmpck(struct snp_guest_dev *snp_dev)
{
- char zero_key[VMPCK_KEY_LEN] = {0};
+ return snp_dev->layout->vmpck0 + snp_dev->vmpck_id * VMPCK_KEY_LEN;
+}

- if (snp_dev->vmpck)
- return !memcmp(snp_dev->vmpck, zero_key, 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;
+}

- return true;
+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);
+
+ return !memcmp(key, zero_key, VMPCK_KEY_LEN);
}

/*
@@ -96,20 +103,22 @@ static bool is_vmpck_empty(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);
- memzero_explicit(snp_dev->vmpck, VMPCK_KEY_LEN);
- snp_dev->vmpck = NULL;
+ u8 *key = snp_get_vmpck(snp_dev);
+
+ dev_alert(snp_dev->dev, "Disabling vmpck_id %u to prevent IV reuse.\n",
+ 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 +146,13 @@ 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 +162,22 @@ 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("VM communication key VMPCK%u is null\n", 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("Crypto context initialization failed\n");
kfree(ctx);
return NULL;
@@ -589,7 +607,7 @@ 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;
@@ -666,32 +684,14 @@ 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, unsigned 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;
}

struct snp_msg_report_resp_hdr {
@@ -727,7 +727,7 @@ static int sev_report_new(struct tsm_report *report, void *data)
guard(mutex)(&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");
return -ENOTTY;
}
@@ -847,22 +847,21 @@ 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) {
- dev_err(dev, "invalid vmpck id %d\n", vmpck_id);
+ snp_dev->layout = layout;
+ if (!snp_assign_vmpck(snp_dev, vmpck_id)) {
+ dev_err(dev, "invalid vmpck id %u\n", vmpck_id);
goto e_unmap;
}

/* Verify that VMPCK is not zero. */
- if (is_vmpck_empty(snp_dev)) {
- dev_err(dev, "vmpck id %d is null\n", vmpck_id);
+ if (snp_is_vmpck_empty(snp_dev)) {
+ dev_err(dev, "vmpck id %u is null\n", vmpck_id);
goto e_unmap;
}

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));
@@ -878,7 +877,7 @@ 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;

@@ -903,7 +902,7 @@ static int __init sev_guest_probe(struct platform_device *pdev)
if (ret)
goto e_free_ctx;

- dev_info(dev, "Initialized SEV guest driver (using vmpck_id %d)\n", vmpck_id);
+ dev_info(dev, "Initialized SEV guest driver (using vmpck_id %u)\n", vmpck_id);
return 0;

e_free_ctx:
--
2.34.1