On Fri, Jun 21, 2024 at 06:08:46PM +0530, Nikunj A Dadhania wrote:
> Currently, SEV guest driver retrieves the pointers to VMPCK and
> os_area_msg_seqno from the secrets page. In order to get rid of this
> dependency,
And we do this because...?
> use vmpck_id to index the appropriate key and the corresponding
> message sequence number.
>
> Signed-off-by: Nikunj A Dadhania <nikunj@xxxxxxx>
> ---
> drivers/virt/coco/sev-guest/sev-guest.c | 74 ++++++++++++-------------
> 1 file changed, 37 insertions(+), 37 deletions(-)
...
> static bool is_vmpck_empty(struct snp_guest_dev *snp_dev)
> {
> char zero_key[VMPCK_KEY_LEN] = {0};
> + u8 *key = get_vmpck(snp_dev);
>
> - if (snp_dev->vmpck)
> - return !memcmp(snp_dev->vmpck, zero_key, VMPCK_KEY_LEN);
> -
> - return true;
> + return !memcmp(key, zero_key, VMPCK_KEY_LEN);
There's a count_nonzero_bytes() function which you can export and use here
instead of expanding the stack unnecessarily.
In any case, there are multiple methods how to check whether a buffer is
zeroes, which are cheaper than this.
> -static u8 *get_vmpck(int id, struct snp_secrets_page *secrets, u32 **seqno)
> +static bool assign_vmpck(struct snp_guest_dev *dev, unsigned int vmpck_id)
> {
> - if (!(id < VMPCK_MAX_NUM))
> - return NULL;
> + if (!(vmpck_id < VMPCK_MAX_NUM))
Yeah, flip that logic.
> + return false;
> +
> + dev->vmpck_id = vmpck_id;
>
> - *seqno = &secrets->os_area.msg_seqno[id];
> - return secrets->vmpck[id];
> + return true;
> }
...
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
