linux-kernel - Re: [PATCH v2 02/11] virt: sev-guest: Move mutex to SNP guest device structure

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Date:   Mon, 3 Apr 2023 14:13:25 -0500
From:   Tom Lendacky <thomas.lendacky@....com>
To:     Nikunj A Dadhania <nikunj@....com>, linux-kernel@...r.kernel.org,
        x86@...nel.org
Cc:     bp@...en8.de, dionnaglaze@...gle.com, pgonda@...gle.com,
        seanjc@...gle.com, pbonzini@...hat.com, michael.roth@....com,
        ketanch@...k.ac.in
Subject: Re: [PATCH v2 02/11] virt: sev-guest: Move mutex to SNP guest device
 structure

On 3/26/23 09:46, Nikunj A Dadhania wrote:
> In preparation to provide new API for sending SNP guest message to the
> sev-guest driver, move the SNP command mutex to the snp_guest_dev
> structure.

In preparation for providing a new API to the sev-guest driver for sending 
an SNP guest message, ...

> 
> Signed-off-by: Nikunj A Dadhania <nikunj@....com>

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

> ---
>   drivers/virt/coco/sev-guest/sev-guest.c | 21 +++++++++++----------
>   1 file changed, 11 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/virt/coco/sev-guest/sev-guest.c b/drivers/virt/coco/sev-guest/sev-guest.c
> index 57af908bafba..6ae197b57644 100644
> --- a/drivers/virt/coco/sev-guest/sev-guest.c
> +++ b/drivers/virt/coco/sev-guest/sev-guest.c
> @@ -35,6 +35,9 @@ struct snp_guest_dev {
>   	struct device *dev;
>   	struct miscdevice misc;
>   
> +	/* Mutex to serialize the shared buffer access and command handling. */
> +	struct mutex cmd_mutex;
> +
>   	void *certs_data;
>   	struct aesgcm_ctx *ctx;
>   	struct snp_guest_msg *request, *response;
> @@ -48,9 +51,6 @@ 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.");
>   
> -/* Mutex to serialize the shared buffer access and command handling. */
> -static DEFINE_MUTEX(snp_cmd_mutex);
> -
>   static inline unsigned int get_ctx_authsize(struct snp_guest_dev *snp_dev)
>   {
>   	if (snp_dev && snp_dev->ctx)
> @@ -99,7 +99,7 @@ static inline u64 __snp_get_msg_seqno(struct snp_guest_dev *snp_dev)
>   {
>   	u64 count;
>   
> -	lockdep_assert_held(&snp_cmd_mutex);
> +	lockdep_assert_held(&snp_dev->cmd_mutex);
>   
>   	/* Read the current message sequence counter from secrets pages */
>   	count = *snp_dev->os_area_msg_seqno;
> @@ -377,7 +377,7 @@ static int get_report(struct snp_guest_dev *snp_dev, struct snp_guest_request_io
>   	struct snp_report_req req;
>   	int rc, resp_len;
>   
> -	lockdep_assert_held(&snp_cmd_mutex);
> +	lockdep_assert_held(&snp_dev->cmd_mutex);
>   
>   	if (!arg->req_data || !arg->resp_data)
>   		return -EINVAL;
> @@ -417,7 +417,7 @@ static int get_derived_key(struct snp_guest_dev *snp_dev, struct snp_guest_reque
>   	/* Response data is 64 bytes and max authsize for GCM is 16 bytes. */
>   	u8 buf[64 + 16];
>   
> -	lockdep_assert_held(&snp_cmd_mutex);
> +	lockdep_assert_held(&snp_dev->cmd_mutex);
>   
>   	if (!arg->req_data || !arg->resp_data)
>   		return -EINVAL;
> @@ -456,7 +456,7 @@ static int get_ext_report(struct snp_guest_dev *snp_dev, struct snp_guest_reques
>   	struct snp_report_resp *resp;
>   	int ret, npages = 0, resp_len;
>   
> -	lockdep_assert_held(&snp_cmd_mutex);
> +	lockdep_assert_held(&snp_dev->cmd_mutex);
>   
>   	if (!arg->req_data || !arg->resp_data)
>   		return -EINVAL;
> @@ -541,12 +541,12 @@ static long snp_guest_ioctl(struct file *file, unsigned int ioctl, unsigned long
>   	if (!input.msg_version)
>   		return -EINVAL;
>   
> -	mutex_lock(&snp_cmd_mutex);
> +	mutex_lock(&snp_dev->cmd_mutex);
>   
>   	/* Check if the VMPCK is not empty */
>   	if (is_vmpck_empty(snp_dev)) {
>   		dev_err_ratelimited(snp_dev->dev, "VMPCK is disabled\n");
> -		mutex_unlock(&snp_cmd_mutex);
> +		mutex_unlock(&snp_dev->cmd_mutex);
>   		return -ENOTTY;
>   	}
>   
> @@ -564,7 +564,7 @@ static long snp_guest_ioctl(struct file *file, unsigned int ioctl, unsigned long
>   		break;
>   	}
>   
> -	mutex_unlock(&snp_cmd_mutex);
> +	mutex_unlock(&snp_dev->cmd_mutex);
>   
>   	if (input.fw_err && copy_to_user(argp, &input, sizeof(input)))
>   		return -EFAULT;
> @@ -683,6 +683,7 @@ static int __init sev_guest_probe(struct platform_device *pdev)
>   		goto e_unmap;
>   	}
>   
> +	mutex_init(&snp_dev->cmd_mutex);
>   	platform_set_drvdata(pdev, snp_dev);
>   	snp_dev->dev = dev;
>   	snp_dev->layout = layout;