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

[wangyanan (Y)]

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@xxxxxxxxxx> 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@xxxxxxxxxx>
> > ---
> >   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? :)

Regards,
Yanan
.
> >    */
> >   struct kvm_pgtable_mm_ops {
> >   	void*		(*zalloc_page)(void *arg);
> > @@ -54,6 +59,8 @@ struct kvm_pgtable_mm_ops {
> >   	int		(*page_count)(void *addr);
> >   	void*		(*phys_to_virt)(phys_addr_t phys);
> >   	phys_addr_t	(*virt_to_phys)(void *addr);
> > +	void		(*flush_dcache)(void *addr, size_t size);
> > +	void		(*flush_icache)(void *addr, size_t size);
> >   };
> >   
> >   /**
> Thanks,
>
> 	M.