Re: [PATCH 1/2] xen: make HYPERVISOR_get_debugreg() always_inline

[Juergen Gross]

On 25.11.21 16:00, Andrew Cooper wrote:
> On 25/11/2021 09:20, Juergen Gross wrote:
> > HYPERVISOR_get_debugreg() is being called from noinstr code, so it
> > should be attributed "always_inline".
> >
> > Fixes: f4afb713e5c3a4419ba ("x86/xen: Make get_debugreg() noinstr")
> > Reported-by: kernel test robot <lkp@xxxxxxxxx>
> > Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> > ---
> >   arch/x86/include/asm/xen/hypercall.h | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/arch/x86/include/asm/xen/hypercall.h b/arch/x86/include/asm/xen/hypercall.h
> > index 0575f5863b7f..28ca1119606b 100644
> > --- a/arch/x86/include/asm/xen/hypercall.h
> > +++ b/arch/x86/include/asm/xen/hypercall.h
> > @@ -287,7 +287,7 @@ HYPERVISOR_set_debugreg(int reg, unsigned long value)
> >   	return _hypercall2(int, set_debugreg, reg, value);
> >   }
> >   
> > -static inline unsigned long
> > +static __always_inline unsigned long
> >   HYPERVISOR_get_debugreg(int reg)
> >   {
> >   	return _hypercall1(unsigned long, get_debugreg, reg);
>
> All this is going to do is push the error one step further in.
>
> Next, objtool will complain that hypercall_page isn't noinstr.

I don't think so:

.pushsection .noinstr.text, "ax"
        .balign PAGE_SIZE
SYM_CODE_START(hypercall_page)
        .rept (PAGE_SIZE / 32)
                UNWIND_HINT_FUNC
                .skip 31, 0x90
                ret
        .endr


Juergen

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