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Tue, 20 Jul 2021 08:04:41 +0000 Received: from mail.kernel.org ([198.145.29.99]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1m5kk0-00C9VY-4K for linux-arm-kernel@lists.infradead.org; Tue, 20 Jul 2021 08:04:38 +0000 Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id D4752610F7; Tue, 20 Jul 2021 08:04:35 +0000 (UTC) Received: from sofa.misterjones.org ([185.219.108.64] helo=why.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1m5kjx-00ESnt-U3; Tue, 20 Jul 2021 09:04:34 +0100 Date: Tue, 20 Jul 2021 09:04:33 +0100 Message-ID: <877dhl9zse.wl-maz@kernel.org> From: Marc Zyngier To: Quentin Perret 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 , Shanker R Donthineni , James Morse , Suzuki K Poulose , Alexandru Elisei , kernel-team@android.com Subject: Re: [PATCH 02/16] KVM: arm64: Don't issue CMOs when the physical address is invalid In-Reply-To: References: <20210715163159.1480168-1-maz@kernel.org> <20210715163159.1480168-3-maz@kernel.org> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/27.1 (x86_64-pc-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: qperret@google.com, 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, vatsa@codeaurora.org, sdonthineni@nvidia.com, james.morse@arm.com, suzuki.poulose@arm.com, alexandru.elisei@arm.com, kernel-team@android.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210720_010436_246774_5BEA2682 X-CRM114-Status: GOOD ( 29.43 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, 19 Jul 2021 18:18:02 +0100, Quentin Perret 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 > > --- > > 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. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel