From: Marc Zyngier <maz@kernel.org>
To: Quentin Perret <qperret@google.com>
Cc: linux-arm-kernel@lists.infradead.org,
kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org,
linux-kernel@vger.kernel.org, will@kernel.org,
dbrazdil@google.com, Srivatsa Vaddagiri <vatsa@codeaurora.org>,
Shanker R Donthineni <sdonthineni@nvidia.com>,
James Morse <james.morse@arm.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Alexandru Elisei <alexandru.elisei@arm.com>,
kernel-team@android.com
Subject: Re: [PATCH 02/16] KVM: arm64: Don't issue CMOs when the physical address is invalid
Date: Tue, 20 Jul 2021 09:04:33 +0100 [thread overview]
Message-ID: <877dhl9zse.wl-maz@kernel.org> (raw)
In-Reply-To: <YPWzykpDMOhT2yh8@google.com>
On Mon, 19 Jul 2021 18:18:02 +0100,
Quentin Perret <qperret@google.com> wrote:
>
> On Thursday 15 Jul 2021 at 17:31:45 (+0100), Marc Zyngier wrote:
> > Make sure we don't issue CMOs when mapping something that
> > is not a memory address in the S2 page tables.
> >
> > Signed-off-by: Marc Zyngier <maz@kernel.org>
> > ---
> > arch/arm64/kvm/hyp/pgtable.c | 16 ++++++++++------
> > 1 file changed, 10 insertions(+), 6 deletions(-)
> >
> > diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
> > index 05321f4165e3..a5874ebd0354 100644
> > --- a/arch/arm64/kvm/hyp/pgtable.c
> > +++ b/arch/arm64/kvm/hyp/pgtable.c
> > @@ -619,12 +619,16 @@ static int stage2_map_walker_try_leaf(u64 addr, u64 end, u32 level,
> > }
> >
> > /* Perform CMOs before installation of the guest stage-2 PTE */
> > - if (mm_ops->dcache_clean_inval_poc && stage2_pte_cacheable(pgt, new))
> > - mm_ops->dcache_clean_inval_poc(kvm_pte_follow(new, mm_ops),
> > - granule);
> > -
> > - if (mm_ops->icache_inval_pou && stage2_pte_executable(new))
> > - mm_ops->icache_inval_pou(kvm_pte_follow(new, mm_ops), granule);
> > + if (kvm_phys_is_valid(phys)) {
> > + if (mm_ops->dcache_clean_inval_poc &&
> > + stage2_pte_cacheable(pgt, new))
> > + mm_ops->dcache_clean_inval_poc(kvm_pte_follow(new,
> > + mm_ops),
> > + granule);
> > + if (mm_ops->icache_inval_pou && stage2_pte_executable(new))
> > + mm_ops->icache_inval_pou(kvm_pte_follow(new, mm_ops),
> > + granule);
> > + }
>
> Hrmpf so this makes me realize we have a problem here, not really caused
> by your patch though.
>
> Specifically, calling kvm_pgtable_stage2_set_owner() can lead to
> overriding valid mappings with invalid mappings, which is effectively an
> unmap operation. In this case we should issue CMOs when unmapping a
> cacheable page to ensure it is clean to the PoC, like the
> kvm_pgtable_stage2_unmap() does.
You only need that if you to have a non-cacheable mapping to the same
page. Otherwise, you will be fine.
For pages that are moved from host-EL1 to EL2, we're good (I don't
think we ever have a non-cachable mapping at EL2). However, once we
start moving pages to guests, we'll need something.
> Note that you patch is already an improvement over the current state of
> things, because calling stage2_pte_cacheable(pgt, new),
> kvm_pte_follow(new, mm_ops) and friends is bogus when 'new' is invalid
Yeah, I had it mentally earmarked as a potential stable candidate. We
may have to do a bit better in the light of the above though.
Thanks,
M.
--
Without deviation from the norm, progress is not possible.
next prev parent reply other threads:[~2021-07-20 8:05 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-15 16:31 [PATCH 00/16] KVM: arm64: MMIO guard PV services Marc Zyngier
2021-07-15 16:31 ` [PATCH 01/16] KVM: arm64: Generalise VM features into a set of flags Marc Zyngier
2021-07-27 18:10 ` Will Deacon
2021-07-28 9:41 ` Marc Zyngier
2021-07-28 14:51 ` Steven Price
2021-07-15 16:31 ` [PATCH 02/16] KVM: arm64: Don't issue CMOs when the physical address is invalid Marc Zyngier
2021-07-19 17:18 ` Quentin Perret
2021-07-20 8:04 ` Marc Zyngier [this message]
2021-07-27 18:10 ` Will Deacon
2021-07-28 9:45 ` Marc Zyngier
2021-07-15 16:31 ` [PATCH 03/16] KVM: arm64: Turn kvm_pgtable_stage2_set_owner into kvm_pgtable_stage2_annotate Marc Zyngier
2021-07-20 10:09 ` Quentin Perret
2021-07-20 10:21 ` Marc Zyngier
2021-07-20 10:38 ` Quentin Perret
2021-07-20 11:20 ` Marc Zyngier
2021-07-20 11:36 ` Quentin Perret
2021-07-20 13:13 ` Marc Zyngier
2021-07-15 16:31 ` [PATCH 04/16] KVM: arm64: Add MMIO checking infrastructure Marc Zyngier
2021-07-20 11:13 ` Quentin Perret
2021-07-20 13:15 ` Marc Zyngier
2021-07-20 15:49 ` Quentin Perret
2021-07-22 18:04 ` Marc Zyngier
2021-07-23 10:16 ` Quentin Perret
2021-07-27 18:11 ` Will Deacon
2021-07-28 9:57 ` Marc Zyngier
2021-07-30 12:26 ` Will Deacon
2021-07-30 13:04 ` Marc Zyngier
2021-07-30 12:58 ` Quentin Perret
2021-07-15 16:31 ` [PATCH 05/16] KVM: arm64: Plumb MMIO checking into the fault handling Marc Zyngier
2021-07-27 18:11 ` Will Deacon
2021-07-28 10:21 ` Marc Zyngier
2021-07-30 12:38 ` Will Deacon
2021-07-15 16:31 ` [PATCH 06/16] KVM: arm64: Force a full unmap on vpcu reinit Marc Zyngier
2021-07-27 18:11 ` Will Deacon
2021-07-28 10:38 ` Marc Zyngier
2021-07-30 12:50 ` Will Deacon
2021-07-15 16:31 ` [PATCH 07/16] KVM: arm64: Wire MMIO guard hypercalls Marc Zyngier
2021-07-27 18:11 ` Will Deacon
2021-07-28 10:47 ` Marc Zyngier
2021-07-30 13:11 ` Will Deacon
2021-08-01 11:20 ` Marc Zyngier
2021-07-15 16:31 ` [PATCH 08/16] KVM: arm64: Add tracepoint for failed MMIO guard check Marc Zyngier
2021-07-15 16:31 ` [PATCH 09/16] KVM: arm64: Advertise a capability for MMIO guard Marc Zyngier
2021-07-15 16:31 ` [PATCH 10/16] KVM: arm64: Add some documentation for the MMIO guard feature Marc Zyngier
2021-07-21 21:17 ` Andrew Jones
2021-07-23 13:30 ` Marc Zyngier
2021-07-23 13:38 ` Andrew Jones
2021-07-23 13:52 ` Marc Zyngier
2021-07-15 16:31 ` [PATCH 11/16] firmware/smccc: Call arch-specific hook on discovering KVM services Marc Zyngier
2021-07-15 16:31 ` [PATCH 12/16] mm/ioremap: Add arch-specific callbacks on ioremap/iounmap calls Marc Zyngier
2021-07-27 18:12 ` Will Deacon
2021-07-28 11:01 ` Marc Zyngier
2021-07-30 14:07 ` Will Deacon
2021-07-15 16:31 ` [PATCH 13/16] arm64: Implement ioremap/iounmap hooks calling into KVM's MMIO guard Marc Zyngier
2021-07-15 16:31 ` [PATCH 14/16] arm64: Enroll into KVM's MMIO guard if required Marc Zyngier
2021-07-15 16:31 ` [PATCH 15/16] arm64: Add a helper to retrieve the PTE of a fixmap Marc Zyngier
2021-07-20 11:16 ` Quentin Perret
2021-07-15 16:31 ` [PATCH 16/16] arm64: Register earlycon fixmap with the MMIO guard Marc Zyngier
2021-07-21 21:42 ` [PATCH 00/16] KVM: arm64: MMIO guard PV services Andrew Jones
2021-07-22 10:00 ` Marc Zyngier
2021-07-22 13:25 ` Andrew Jones
2021-07-22 15:30 ` Marc Zyngier
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