linux-kernel - Re: [PATCH RFC v8 03/56] KVM: x86: Add platform hooks for private memory invalidations

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Date:   Fri, 17 Mar 2023 22:13:22 -0700
From:   Isaku Yamahata <isaku.yamahata@...il.com>
To:     Michael Roth <michael.roth@....com>
Cc:     kvm@...r.kernel.org, linux-coco@...ts.linux.dev,
        linux-mm@...ck.org, linux-crypto@...r.kernel.org, x86@...nel.org,
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        dgilbert@...hat.com, jarkko@...nel.org, ashish.kalra@....com,
        nikunj.dadhania@....com, isaku.yamahata@...il.com
Subject: Re: [PATCH RFC v8 03/56] KVM: x86: Add platform hooks for private
 memory invalidations

On Mon, Feb 20, 2023 at 12:37:54PM -0600,
Michael Roth <michael.roth@....com> wrote:

> In some cases, like with SEV-SNP, guest memory needs to be updated in a
> platform-specific manner before it can be safely freed back to the host.
> Add hooks to wire up handling of this sort to the invalidation notifiers
> for restricted memory.
> 
> Also issue invalidations of all allocated pages during notifier/memslot
> unbinding so that the pages are not left in an unusable state when
> they eventually get freed back to the host upon FD release.

I'm just curios. Could you please elaborate?
Unbind is happen only when memory slot is delete or vm is destroyed.  In the
case of memory slot deletion, the gpa region is zapped via
kvm_arch_commit_memory_region().  In the case of VM destroy, we have
kvm_flush_shadow_all() which calls
kvm_arch_flush_shadow_all() =>kvm_mmu_zap_all().  Doesn't it work?

Thanks,
-- 
Isaku Yamahata <isaku.yamahata@...il.com>