From: Quentin Perret <qperret@google.com>
To: Peter Collingbourne <pcc@google.com>
Cc: kvmarm@lists.cs.columbia.edu, Marc Zyngier <maz@kernel.org>,
kvm@vger.kernel.org, Andy Lutomirski <luto@amacapital.net>,
linux-arm-kernel@lists.infradead.org,
Michael Roth <michael.roth@amd.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Chao Peng <chao.p.peng@linux.intel.com>,
Will Deacon <will@kernel.org>,
Evgenii Stepanov <eugenis@google.com>
Subject: Re: [PATCH 1/3] KVM: arm64: add a hypercall for disowning pages
Date: Thu, 23 Jun 2022 13:11:54 +0000 [thread overview]
Message-ID: <YrRmmrY24Pv6hyAO@google.com> (raw)
In-Reply-To: <20220623021926.3443240-2-pcc@google.com>
Hi Peter,
On Wednesday 22 Jun 2022 at 19:19:24 (-0700), Peter Collingbourne wrote:
> @@ -677,9 +678,9 @@ static bool stage2_pte_is_counted(kvm_pte_t pte)
> /*
> * The refcount tracks valid entries as well as invalid entries if they
> * encode ownership of a page to another entity than the page-table
> - * owner, whose id is 0.
> + * owner, whose id is 0, or NOBODY, which does not correspond to a page-table.
> */
> - return !!pte;
> + return !!pte && pte != kvm_init_invalid_leaf_owner(PKVM_ID_NOBODY);
> }
I'm not sure to understand this part? By not refcounting the PTEs that
are annotated with PKVM_ID_NOBODY, the page-table page that contains
them may be freed at some point. And when that happens, I don't see how
the hypervisor will remember to block host accesses to the disowned
pages.
Cheers,
Quentin
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2022-06-23 13:13 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-23 2:19 [PATCH 0/3] KVM: arm64: support MTE in protected VMs Peter Collingbourne
2022-06-23 2:19 ` [PATCH 1/3] KVM: arm64: add a hypercall for disowning pages Peter Collingbourne
2022-06-23 13:11 ` Quentin Perret [this message]
2022-06-23 18:12 ` Peter Collingbourne
2022-06-23 2:19 ` [PATCH 2/3] KVM: arm64: disown unused reserved-memory regions Peter Collingbourne
2022-06-23 2:19 ` [PATCH 3/3] KVM: arm64: allow MTE in protected VMs if the tag storage is known Peter Collingbourne
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=YrRmmrY24Pv6hyAO@google.com \
--to=qperret@google.com \
--cc=catalin.marinas@arm.com \
--cc=chao.p.peng@linux.intel.com \
--cc=eugenis@google.com \
--cc=kvm@vger.kernel.org \
--cc=kvmarm@lists.cs.columbia.edu \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=luto@amacapital.net \
--cc=maz@kernel.org \
--cc=michael.roth@amd.com \
--cc=pcc@google.com \
--cc=will@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).