linux-kernel - Re: [PATCH] acpi, apei, arm64: APEI initial support for aarch64.

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Date:	Tue, 18 Aug 2015 17:26:26 +0800
From:	Fu Wei <fu.wei@...aro.org>
To:	Will Deacon <will.deacon@....com>
Cc:	"Zhang, Jonathan Zhixiong" <zjzhang@...eaurora.org>,
	"harba@...eaurora.org" <harba@...eaurora.org>,
	"linaro-acpi@...ts.linaro.org" <linaro-acpi@...ts.linaro.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"matt.fleming@...el.com" <matt.fleming@...el.com>,
	"tekkamanninja@...il.com" <tekkamanninja@...il.com>,
	"graeme.gregory@...aro.org" <graeme.gregory@...aro.org>,
	"al.stone@...aro.org" <al.stone@...aro.org>,
	"hanjun.guo@...aro.org" <hanjun.guo@...aro.org>,
	"jcm@...hat.com" <jcm@...hat.com>,
	Mark Rutland <Mark.Rutland@....com>,
	Catalin Marinas <Catalin.Marinas@....com>,
	"rjw@...ysocki.net" <rjw@...ysocki.net>,
	"bp@...en8.de" <bp@...en8.de>,
	Tomasz Nowicki <tomasz.nowicki@...aro.org>
Subject: Re: [PATCH] acpi, apei, arm64: APEI initial support for aarch64.

Hi

On 18 August 2015 at 16:31, Will Deacon <will.deacon@....com> wrote:
> On Tue, Aug 18, 2015 at 12:19:13AM +0100, Zhang, Jonathan Zhixiong wrote:
>> On 8/17/2015 3:01 AM, Will Deacon wrote:
>> > On Fri, Aug 14, 2015 at 01:35:53PM +0100, fu.wei@...aro.org wrote:
>> >> diff --git a/arch/arm64/include/asm/acpi.h b/arch/arm64/include/asm/acpi.h
>> >> index a17b623..ced6e25 100644
>> >> --- a/arch/arm64/include/asm/acpi.h
>> >> +++ b/arch/arm64/include/asm/acpi.h
>> >> @@ -22,6 +22,7 @@
>> >>   #ifdef CONFIG_ACPI_APEI
>> >>   #include <linux/efi.h>
>> >>   #include <asm/pgtable.h>
>> >> +#include <asm/tlbflush.h>
>> >>   #endif
>> >>
>> >>   /* Macros for consistency checks of the GICC subtable of MADT */
>> >> @@ -52,6 +53,9 @@ typedef u64 phys_cpuid_t;
>> >>   extern int acpi_disabled;
>> >>   extern int acpi_noirq;
>> >>   extern int acpi_pci_disabled;
>> >> +#ifdef CONFIG_ACPI_APEI
>> >> +extern int acpi_disable_cmcff;
>> >> +#endif
>> >>
>> >>   static inline void disable_acpi(void)
>> >>   {
>> >> @@ -89,6 +93,13 @@ static inline bool acpi_has_cpu_in_madt(void)
>> >>   static inline void arch_fix_phys_package_id(int num, u32 slot) { }
>> >>   void __init acpi_init_cpus(void);
>> >>
>> >> +#ifdef CONFIG_ACPI_APEI
>> >> +static inline void arch_apei_flush_tlb_one(unsigned long addr)
>> >> +{
>> >> +  flush_tlb_kernel_range(addr, addr + PAGE_SIZE);
>> >> +}
>> >> +#endif
>> >
>> > Looking at the callers of this function, I suspect we could downgrade it
>> > to a local CPU invalidation if we wanted. However, this isn't a hot-path
>> > so it's fine to stay like it is for now.
>> I suppose if we run "tlbi vae1" instead of "tlbi vae1is", it will be
>> more efficient without side effect, since both ghes_ioremap_pfn_irq()
>> and ghes_iounmap_irq() happen in same atomic context. However, today
>> arch/arm64/include/asm/tlbflush.h does not have a function tailored for
>> such performance optimization. Does it make sense to add a parameter to
>> flush_tlb_kernel_range() to allow caller to make a choice?
>>    static inline void flush_tlb_kernel_range(unsigned long start,
>>       unsigned long end, bool local)
>> There are only two others callers of flush_tlb_kernel_range().
>
> I've already got some patches to add things like local_flush_tlb_all,
> which I'll post after the merge window (I'm currently rewriting a bunch
> of the switch_mm code to try to reduce the TLBI traffic).

If I understand correctly, these patches add new  functions, instead
of changing the existent one.
I thinks this way is better.

If we have new patch for optimizing TLB flushing, we can make a new
patchset for this in the future.
Because this patch is only for enabling APEI on aarch64.

>
> If this isn't a hotpath (I don't think it is), then it's probably not
> worth making the optimisation without a system to benchmark it on.

agree.

But please let me know if you have any suggestion on this patch.
is this patch OK for you?

>
> Will



-- 
Best regards,

Fu Wei
Software Engineer
Red Hat Software (Beijing) Co.,Ltd.Shanghai Branch
Ph: +86 21 61221326(direct)
Ph: +86 186 2020 4684 (mobile)
Room 1512, Regus One Corporate Avenue,Level 15,
One Corporate Avenue,222 Hubin Road,Huangpu District,
Shanghai,China 200021
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