[PATCH] ARM64: KVM: Fix coherent_icache_guest_page() for host with external L3-cache.

[Anup Patel]

On Wed, Aug 14, 2013 at 7:53 PM, Sudeep KarkadaNagesha
<Sudeep.KarkadaNagesha at arm.com> wrote:
> On 14/08/13 12:47, Pranavkumar Sawargaonkar wrote:
>> Systems with large external L3-cache (few MBs), might have dirty
>> content belonging to the guest page in L3-cache. To tackle this,
>> we need to flush such dirty content from d-cache so that guest
>> will see correct contents of guest page when guest MMU is disabled.
>>
>> The patch fixes coherent_icache_guest_page() for external L3-cache.
>>
>
> I don't understand KVM but the commit message caught my attention.
>
> You are referring to clean the external/outer L3 cache but using
> internal cache maintenance APIs. You should be using outer_cache APIs if
> you really intend to do outer cache maintenance ?
> Is the external/outer L3 cache not unified ?
>
> Or did you mean to flush d-cache to the point of coherency(external L3
> in your case)? If so it's not clear from the commit log.

Yes, we mean to flush d-cache to the point of coherency (which in our
case is external L3-cache).

The patch description is more in-terms of KVM virtualization but, we
can certainly add more details.

>
> Regards,
> Sudeep
>
>> Signed-off-by: Pranavkumar Sawargaonkar <pranavkumar at linaro.org>
>> Signed-off-by: Anup Patel <anup.patel at linaro.org>
>> ---
>>  arch/arm64/include/asm/kvm_mmu.h |    2 ++
>>  1 file changed, 2 insertions(+)
>>
>> diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
>> index efe609c..5129038 100644
>> --- a/arch/arm64/include/asm/kvm_mmu.h
>> +++ b/arch/arm64/include/asm/kvm_mmu.h
>> @@ -123,6 +123,8 @@ static inline void coherent_icache_guest_page(struct kvm *kvm, gfn_t gfn)
>>       if (!icache_is_aliasing()) {            /* PIPT */
>>               unsigned long hva = gfn_to_hva(kvm, gfn);
>>               flush_icache_range(hva, hva + PAGE_SIZE);
>> +             /* Flush d-cache for systems with external caches. */
>> +             __flush_dcache_area((void *) hva, PAGE_SIZE);
>>       } else if (!icache_is_aivivt()) {       /* non ASID-tagged VIVT */
>>               /* any kind of VIPT cache */
>>               __flush_icache_all();
>>
>
>
>
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Regards,
Anup