lkml.org 
[lkml]   [2020]   [Oct]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [PATCH v2 3/5] x86/boot/compressed/64: Check SEV encryption in 64-bit boot-path
On Tue, Oct 20, 2020 at 05:48:12PM +0200, Joerg Roedel wrote:
> On Tue, Oct 20, 2020 at 10:12:59AM -0400, Arvind Sankar wrote:
> > On Tue, Oct 20, 2020 at 02:18:54PM +0200, Joerg Roedel wrote:
> > Why use r10-r12 rather than the caller-save registers? Even for the head
> > code where you need to perserve the cr3 value you can just return it in
> > rax?
>
> It can surely be optimized, but it makes the code less robust. This
> function is only called from assembly so the standard x86-64 calling
> conventions might not be followed strictly. I think its better to make
> as few assumptions as possible about the calling code to avoid
> regressions. Changes to the head code are not necessarily tested with
> SEV/SEV-ES guests by developers.
>
> Regards,
>
> Joerg

This is called from both assembly and C, but anyway, you're already
assuming r10 and r11 can be clobbered safely, and you just took out the
save/restores in set_sev_encryption_mask, which is actually called only
from assembly.

\
 
 \ /
  Last update: 2020-10-20 18:05    [W:0.041 / U:0.228 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site