linux-kernel - Re: [PATCH v3 05/14] virt: sev-guest: Add vmpck_id to snp_guest

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Message-ID: <1a4e6652-2e24-955c-5332-da84cced68e4@amd.com>
Date:   Tue, 1 Aug 2023 11:30:07 -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
Subject: Re: [PATCH v3 05/14] virt: sev-guest: Add vmpck_id to snp_guest_dev
 struct

On 7/22/23 06:19, 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.
> 
> Signed-off-by: Nikunj A Dadhania <nikunj@....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)

I noticed this name change from is_vmpck_empty() to snp_is_vmpck_empty(). 
Is that in prep for moving, too? Is so, maybe call that out in the commit 
message.

>   {
>   	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);

I believe key can't be NULL, so this check isn't required.

Thanks,
Tom

>   
>   	return true;
>   }