Re: [PATCH v6 1/4] KVM: arm64: Introduce cache maintenance callbacks for guest stage-2

Marc Zyngier
2021-06-17T08:03:19Z

On Thu, 17 Jun 2021 07:48:29 +0100,
"wangyanan (Y)" <wangyanan55@huawei.com> wrote:
>
> Hi Marc,
>
> On 2021/6/16 21:21, Marc Zyngier wrote:
> > Hi Yanan,
> >
> > On Wed, 16 Jun 2021 10:51:57 +0100,
> > Yanan Wang <wangyanan55@huawei.com> wrote:
> >> To prepare for performing guest CMOs in the fault handlers in pgtable.c,
> >> introduce two cache maintenance callbacks in struct kvm_pgtable_mm_ops.
> >>
> >> The new callbacks are specific for guest stage-2, so they will only be
> >> initialized in 'struct kvm_pgtable_mm_ops kvm_s2_mm_ops'.
> >>
> >> Signed-off-by: Yanan Wang <wangyanan55@huawei.com>
> >> ---
> >> arch/arm64/include/asm/kvm_pgtable.h | 7 +++++++
> >> 1 file changed, 7 insertions(+)
> >>
> >> diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h
> >> index c3674c47d48c..302eca32e0af 100644
> >> --- a/arch/arm64/include/asm/kvm_pgtable.h
> >> +++ b/arch/arm64/include/asm/kvm_pgtable.h
> >> @@ -44,6 +44,11 @@ typedef u64 kvm_pte_t;
> >> * in the current context.
> >> * @virt_to_phys: Convert a virtual address mapped in the current context
> >> * into a physical address.
> >> + * @flush_dcache: Clean data cache for a guest page address range before
> >> + * creating the corresponding stage-2 mapping.
> > Please don't reintroduce the word 'flush'. We are really trying to
> > move away from it as it doesn't describe what we want to do.
> I agree with this. I intended to make the names short and laconic, but this
> missed the information about the callback's actual behaviors.
> > Here this
> > should be 'clean_invalidate_dcache' which, despite being a mouthful,
> > describe accurately what we expect it to do.
> Sure, I will change the name as you suggested.
> > The comment is also missing the invalidate part, and we shouldn't
> > assume that this is only used for S2 mapping.
> Ok, will refine the comment. I think something like"Clean and invalidate the
> date cache for the specified memory address range" may be generic enough.
> >> + * @flush_icache: Invalidate instruction cache for a guest page address
> >> + * range before creating or updating the corresponding
> >> + * stage-2 mapping.
> > Same thing here; this should be 'invalidate_icache', and the comment
> > cleaned up.
> Thanks, I will also correct this part.
>
> Besides the callback names and comments, is there anything else that still
> needs some adjustment in the other three patches? :)

It looks pretty good so far, much nicer than the previous versions.

I have a small nit on the last patch, which should be dead easy to
address. I'm currently running a bunch of tests, hopefully nothing bad
will come out of it.

If you respin it shortly, that nothing fails, and unless someone
shouts, I'll queue it for -next.

Thanks,

M.

--
Without deviation from the norm, progress is not possible.