linux-kernel - Re: [PATCHv2 1/5] efi/runtime-wrappers: add {__,}efi_call

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Message-ID: <20160421141952.GQ6879@leverpostej>
Date:	Thu, 21 Apr 2016 15:19:53 +0100
From:	Mark Rutland <mark.rutland@....com>
To:	Leif Lindholm <leif.lindholm@...aro.org>
Cc:	linux-efi@...r.kernel.org, ard.biesheuvel@...aro.org,
	catalin.marinas@....com, hpa@...or.com, linux@....linux.org.uk,
	matt@...eblueprint.co.uk, mingo@...hat.com, tglx@...utronix.de,
	will.deacon@....com, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv2 1/5] efi/runtime-wrappers: add {__,}efi_call_virt
 templates

On Thu, Apr 21, 2016 at 01:55:07PM +0100, Mark Rutland wrote:
> 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@....com>
> > > Cc: Matt Fleming <matt@...eblueprint.co.uk>
> > > Cc: linux-efi@...r.kernel.org
> > > Cc: linux-kernel@...r.kernel.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.

Actually, ia64 never uses this code, so I can add a final patch to
remove the ifdefs after the existing arch code is moved over.

I'll do that...

Mark.