Re: [Xen-devel] [PATCH v2 14/16] x86: make entry point code build when !CONFIG_PV

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Mon, Oct 29, 2018 at 09:03:18AM -0600, Jan Beulich wrote:
> >>> On 19.10.18 at 16:28, <wei.liu2@xxxxxxxxxx> wrote:
> > @@ -548,10 +550,14 @@ ENTRY(ret_from_intr)
> >          GET_CURRENT(bx)
> >          testb $3, UREGS_cs(%rsp)
> >          jz    restore_all_xen
> > +#ifdef CONFIG_PV
> >          movq  VCPU_domain(%rbx), %rax
> >          cmpb  $0, DOMAIN_is_32bit_pv(%rax)
> >          je    test_all_events
> >          jmp   compat_test_all_events
> > +#else
> > +        BUG
> > +#endif
> 
> Hmm, not sure here (and elsewhere): Another option is to
> streamline execution by replacing the conditional branch with an
> unconditional one in the !PV case. Andrew, do you have any
> thoughts either way?

My original thought was to catch potential issues in Xen code which
messes up with the permission level.  Using unconditional jump is fine
by me, too. But in that case I will seek to at least add an assertion
for debug build.

Wei.

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