Re: [PATCHv2 1/5] efi/runtime-wrappers: add {__,}efi_call_virt templates

Mark Rutland
2016-04-21T12:55:07Z

On Thu, Apr 21, 2016 at 12:42:56PM +0100, Leif Lindholm wrote:
> On Thu, Apr 21, 2016 at 12:35:25PM +0100, Mark Rutland wrote:
> > Currently each architecture must implement two macros, efi_call_virt and
> > __efi_call_virt, which only differ by the presence or absence of a
> > return type. Otherwise, the logic surrounding the call is identical.
> >
> > As each architecture must define the entire body of each, we can't place
> > any generic manipulation (e.g. irq flag validation) in the middle.
> >
> > This patch adds template implementations of these macros. With these,
> > arch code can implement three template macros, avoiding reptition for
> > the void/non-void return cases:
> >
> > * arch_efi_call_virt_setup
> >
> > Sets up the environment for the call (e.g. switching page tables,
> > allowing kernel-mode use of floating point, if required).
> >
> > * arch_efi_call_virt
> >
> > Performs the call. The last expression in the macro must be the call
> > itself, allowing the logic to be shared by the void and non-void
> > cases.
> >
> > * arch_efi_call_virt_teardown
> >
> > Restores the usual kernel environment once the call has returned.
> >
> > While the savings from repition are minimal, we additionally gain the
> > ability to add common code around the call with the call enviroment set
> > up. This can be used to detect common firmware issues (e.g. bad irq mask
> > management).
> >
> > Signed-off-by: Mark Rutland <mark.rutland-5wv7dgnIgG8@public.gmane.org>
> > Cc: Matt Fleming <matt-mF/unelCI9GS6iBeEJttW/XRex20P6io@public.gmane.org>
> > Cc: linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
> > Cc: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
> > ---
> > drivers/firmware/efi/runtime-wrappers.c | 21 +++++++++++++++++++++
> > 1 file changed, 21 insertions(+)
> >
> > diff --git a/drivers/firmware/efi/runtime-wrappers.c b/drivers/firmware/efi/runtime-wrappers.c
> > index de69530..1b9fa54 100644
> > --- a/drivers/firmware/efi/runtime-wrappers.c
> > +++ b/drivers/firmware/efi/runtime-wrappers.c
> > @@ -20,6 +20,27 @@
> > #include <linux/spinlock.h>
> > #include <asm/efi.h>
> >
> > +
> > +#ifndef efi_call_virt
>
> So ... not a strong complaint, but I would prefer if these weren't
> ifdefd. I presume this is because ia64?

Yup, and to allow the gradual migration of arm/arm64/x86 without a new
CONFIG_WANT_GENERIC_EFI_CALL_VIRT or something to that effect.

> Could that be given a dummy pass-through version instead?

I'm not exactly sure what you mean by that. Could you elaborate?

> If not, could a comment be added that this is to retain compatibility
> with ia64 (so that if that architecture was to mysteriously disappear
> from the tree, someone might remember to deconditionalise it)?

Sure. I can also add a note to the commit message regarding the
temporary need while arm/arm64/x86 are moved over.

Thanks,
Mark.

> > +#define efi_call_virt(f, args...) \
> > +({ \
> > + efi_status_t __s; \
> > + arch_efi_call_virt_setup(); \
> > + __s = arch_efi_call_virt(f, args); \
> > + arch_efi_call_virt_teardown(); \
> > + __s; \
> > +})
> > +#endif
> > +
> > +#ifndef __efi_call_virt
> > +#define __efi_call_virt(f, args...) \
> > +({ \
> > + arch_efi_call_virt_setup(); \
> > + arch_efi_call_virt(f, args); \
> > + arch_efi_call_virt_teardown(); \
> > +})
> > +#endif
> > +
> > /*
> > * According to section 7.1 of the UEFI spec, Runtime Services are not fully
> > * reentrant, and there are particular combinations of calls that need to be
> > --
> > 1.9.1
> >
>