Re: [PATCH v5 05/14] virt: sev-guest: Add vmpck_id to snp_guest_dev struct

[Tom Lendacky <thomas.lendacky@xxxxxxx>]

On 10/30/23 01:36, Nikunj A Dadhania wrote:
> 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@xxxxxxx>

With the fix to the snp_assign_vmpck() to change the int to an unsigned 
int as requested by Dionna...

Reviewed-by: Tom Lendacky <thomas.lendacky@xxxxxxx>

> ---
>   drivers/virt/coco/sev-guest/sev-guest.c | 85 ++++++++++++-------------
>   1 file changed, 42 insertions(+), 43 deletions(-)
>
> diff --git a/drivers/virt/coco/sev-guest/sev-guest.c b/drivers/virt/coco/sev-guest/sev-guest.c
> index 5801dd52ffdf..4dd094c73e2f 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;
> @@ -61,14 +60,22 @@ MODULE_PARM_DESC(vmpck_id, "The VMPCK ID to use when communicating with the PSP.
>   /* Mutex to serialize the shared buffer access and command handling. */
>   static DEFINE_MUTEX(snp_cmd_mutex);
>   
> -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);
>   }
>   
>   /*
> @@ -90,20 +97,22 @@ 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;
>   }
> @@ -131,11 +140,13 @@ 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)
> @@ -145,15 +156,22 @@ 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;
> @@ -586,7 +604,7 @@ 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;
> @@ -656,32 +674,14 @@ 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)
> @@ -713,14 +713,14 @@ 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;
>   	}
> @@ -728,7 +728,6 @@ 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));
> @@ -744,7 +743,7 @@ 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;
>