linux-kernel - Re: [PATCH v3 1/1] KVM: arm64: Allow cacheable stage 2 mapping using VMA flags

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Date: Wed, 26 Mar 2025 08:31:32 +0000
From: Ankit Agrawal <ankita@...dia.com>
To: Catalin Marinas <catalin.marinas@....com>, Jason Gunthorpe
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CC: Oliver Upton <oliver.upton@...ux.dev>, Marc Zyngier <maz@...nel.org>,
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Subject: Re: [PATCH v3 1/1] KVM: arm64: Allow cacheable stage 2 mapping using
 VMA flags

> On Wed, Mar 19, 2025 at 04:22:46PM -0300, Jason Gunthorpe wrote:
> > On Wed, Mar 19, 2025 at 06:11:02PM +0000, Catalin Marinas wrote:
> > > On Wed, Mar 19, 2025 at 02:04:29PM -0300, Jason Gunthorpe wrote:
> > > > On Wed, Mar 19, 2025 at 12:01:29AM -0700, Oliver Upton wrote:
> > > > > You have a very good point that KVM is broken for cacheable PFNMAP'd
> > > > > crap since we demote to something non-cacheable, and maybe that
> > > > > deserves fixing first. Hopefully nobody notices that we've taken away
> > > > > the toys...
> > > >
> > > > Fixing it is either faulting all access attempts or mapping it
> > > > cachable to the S2 (as this series is trying to do)..
> > >
> > > As I replied earlier, it might be worth doing both - fault on !FWB
> > > hardware (or rather reject the memslot creation), cacheable S2
> > > otherwise.
> >
> > I have no objection, Ankit are you able to make a failure patch?
>
> I'd wait until the KVM maintainers have their say.
> 

Maz, Oliver any thoughts on this? Can we conclude to create this failure
patch in memslot creation?


> --
> Catalin