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

Leif Lindholm
2016-04-21T11:43:03Z

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@arm.com>
> Cc: Matt Fleming <matt@codeblueprint.co.uk>
> Cc: linux-efi@vger.kernel.org
> Cc: linux-kernel@vger.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?
Could that be given a dummy pass-through version instead? 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)?

> +#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
>