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SubjectRe: [PATCH v2 RESEND 1/2] x86/UV: Introduce a helper function to check UV system at earlier stage
Cc linux-efi list
On 09/14/17 at 04:08pm, Baoquan He wrote:
> On 09/14/17 at 03:49pm, Dave Young wrote:
> > > > diff --git a/arch/x86/include/asm/uv/uv.h b/arch/x86/include/asm/uv/uv.h
> > > > index b5a32231abd8..93d7ad8763ba 100644
> > > > --- a/arch/x86/include/asm/uv/uv.h
> > > > +++ b/arch/x86/include/asm/uv/uv.h
> > > > @@ -18,6 +18,11 @@ extern void uv_nmi_init(void);
> > > > extern void uv_system_init(void);
> > > > extern const struct cpumask *uv_flush_tlb_others(const struct cpumask *cpumask,
> > > > const struct flush_tlb_info *info);
> > > > +#include <linux/efi.h>
> > > > +static inline int is_early_uv_system(void)
> > > > +{
> > > > + return !((efi.uv_systab == EFI_INVALID_TABLE_ADDR) || !efi.uv_systab);
> > > > +}
> >
>
> Thanks for looking into this, Dave!
>
> >
> > Sorry for jumping in late, I have two questions about the patch:
> >
> > 1) For efi tables, the only invalid value is EFI_INVALID_TABLE_ADDR, and
> > efi struct is initialized as EFI_INVALID_TABLE_ADDR by default so no
> > need to check "|| !efi.uv_systab". Do we have any UV firmware specific
> > assumption that "0" is also possible to be assigned?
>
> Hmm, in uv_bios_init() it also checks the !efi.uv_systab case. And
> EFI_INVALID_TABLE_ADDR checking is earlier, it won't affect the result
> if it's EFI_INVALID_TABLE_ADDR. And !efi.uv_systab can make it safer
> since it doesn't work either if efi.uv_systab is 0. Mainly it's not
> harmful.
>
> Mike, what's your thought? Should I only check the (efi.uv_systab ==
> EFI_INVALID_TABLE_ADDR) case?
>
> >
> > 2) It seems adding this function in uv.h for separating this for uv
> > system only purpose. But I feel it is better to put it in efi.h instead.
>
> At the beginning I put it in efi.c, later Mike suggested putting it in
> asm/uv/uv.h. You can also find the discussion in below link.
> https://patchwork.kernel.org/patch/9732787/
>
> Thanks
> Baoquan
>
> >
> > uv_systab is already a member of struct efi, it is in efi.h so it is
> > natural to check the table exist or not. Then just include efi.h in
> > kaslr.c and use the function.
> >
> > something like drivers/firmware/efi/esrt.c: esrt_table_exists()
> >
> > Anyway I have no strong opinon, it looks more natural to me though.
> >
> > > >
> > > > #else /* X86_UV */
> > > >
> > > > @@ -30,6 +35,7 @@ static inline const struct cpumask *
> > > > uv_flush_tlb_others(const struct cpumask *cpumask,
> > > > const struct flush_tlb_info *info)
> > > > { return cpumask; }
> > > > +static inline int is_early_uv_system(void) { return 0; }
> > > >
> > > > #endif /* X86_UV */
> > > >
> > > > --
> > > > 2.5.5
> > > >
> >
> > Thanks
> > Dave

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