[lkml]   [2018]   [Jan]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH 03/24] x86/paravirt: Annotate indirect calls
On 25/01/18 11:22, Peter Zijlstra wrote:
> On Thu, Jan 25, 2018 at 10:02:05AM +0000, David Woodhouse wrote:
>> On Tue, 2018-01-23 at 16:25 +0100, Peter Zijlstra wrote:
>>> Paravirt emits indirect calls which get flagged by objtool retpoline
>>> checks, annotate it away because all these indirect calls will be
>>> patched out before we start userspace.
>> I've seen this asserted repeatedly but I've never truly convinced
>> myself of it. Is this absolutely unconditionally true in every case,
>> even when we're running as a guest and there are *actual* calls to be
>> made? We turn them into direct calls, never leave them indirect?
> That is my understanding; and when I worked on the paravirt spinlock
> code and disassembled live guest code this seemed to have happend.
> But let me go read the paravirt code again to make a stronger argument
> in favour.

paravirt_patch_default() is the function you want to look at: it either
replaces the indirect call by some cutom code (which is never an
indirect call) or by a call of the target function.


 \ /
  Last update: 2018-01-25 11:27    [W:0.063 / U:5.240 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site