linux-kernel - Re: [PATCHv2 1/6] efi/runtime-wrappers: add {__,}efi_call

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Date:	Sun, 24 Apr 2016 22:12:12 +0100
From:	Matt Fleming <matt@...eblueprint.co.uk>
To:	Mark Rutland <mark.rutland@....com>
Cc:	linux-efi@...r.kernel.org, ard.biesheuvel@...aro.org,
	catalin.marinas@....com, hpa@...or.com, leif.lindholm@...aro.org,
	linux-arm-kernel@...ts.infradead.org, linux@....linux.org.uk,
	linux-kernel@...r.kernel.org, mingo@...hat.com, tglx@...utronix.de,
	will.deacon@....com
Subject: Re: [PATCHv2 1/6] efi/runtime-wrappers: add {__,}efi_call_virt
 templates

On Fri, 22 Apr, at 02:51:18PM, 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 environment 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>
> Reviewed-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
> 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(+)

Applied. I incorporated the explanation of the 3 template macros next
to the code because it is too useful to only have it exist in the git
commit history.