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

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Date:   Thu, 3 Aug 2023 10:32:50 +0530
From:   "Nikunj A. Dadhania" <nikunj@....com>
To:     Tom Lendacky <thomas.lendacky@....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 8/2/2023 10:25 PM, Tom Lendacky wrote:
> On 8/1/23 23:12, Nikunj A. Dadhania wrote:
>> On 8/1/2023 10:00 PM, Tom Lendacky wrote:
>>> 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.
>>
>> Yes, will add to the  commit.
>>
>>>
>>>>    {
>>>>        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.
>>
>> Sure, will update.
> 
> Ah, although I noticed that when the various functions are moved over to the other file, the key return value can be NULL, so probably not worth changing here.

I have removed the check in this patch, but the check is retained in the later patch where key can be NULL.

Regards
Nikunj