Messages in this thread |  | | Subject | Re: [PATCH 03/24] x86/paravirt: Annotate indirect calls | From | Juergen Gross <> | Date | Thu, 25 Jan 2018 11:26:57 +0100 |
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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.
Juergen
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