Re: [PATCH 3/5] crypto: ccp: Play nice with vmalloc'd memory for SEV command structs

Sean Christopherson
2021-04-05T15:07:02Z

On Sun, Apr 04, 2021, Christophe Leroy wrote:
>
> Le 03/04/2021 à 01:37, Sean Christopherson a écrit :
> > @@ -152,11 +153,21 @@ static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret)
> > sev = psp->sev_data;
> > buf_len = sev_cmd_buffer_len(cmd);
> > - if (WARN_ON_ONCE(!!data != !!buf_len))
> > + if (WARN_ON_ONCE(!!__data != !!buf_len))
> > return -EINVAL;
> > - if (WARN_ON_ONCE(data && is_vmalloc_addr(data)))
> > - return -EINVAL;
> > + if (__data && is_vmalloc_addr(__data)) {
> > + /*
> > + * If the incoming buffer is virtually allocated, copy it to
> > + * the driver's scratch buffer as __pa() will not work for such
> > + * addresses, vmalloc_to_page() is not guaranteed to succeed,
> > + * and vmalloc'd data may not be physically contiguous.
> > + */
> > + data = sev->cmd_buf;
> > + memcpy(data, __data, buf_len);
> > + } else {
> > + data = __data;
> > + }
>
> I don't know how big commands are, but if they are small, it would probably
> be more efficient to inconditionnally copy them to the buffer rather then
> doing the test.

Brijesh, I assume SNP support will need to copy the commands unconditionally? If
yes, it probably makes sense to do so now and avoid vmalloc dependencies
completely. And I think that would allow for the removal of status_cmd_buf and
init_cmd_buf, or is there another reason those dedicated buffers exist?