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[35.233.69.230]) by smtp.gmail.com with ESMTPSA id j6sm218657wmq.16.2021.03.15.09.53.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 15 Mar 2021 09:53:20 -0700 (PDT) Date: Mon, 15 Mar 2021 16:53:18 +0000 From: Quentin Perret To: Will Deacon Cc: catalin.marinas@arm.com, maz@kernel.org, james.morse@arm.com, julien.thierry.kdev@gmail.com, suzuki.poulose@arm.com, android-kvm@google.com, seanjc@google.com, mate.toth-pal@arm.com, linux-kernel@vger.kernel.org, robh+dt@kernel.org, linux-arm-kernel@lists.infradead.org, kernel-team@android.com, kvmarm@lists.cs.columbia.edu, tabba@google.com, ardb@kernel.org, mark.rutland@arm.com, dbrazdil@google.com Subject: Re: [PATCH v5 29/36] KVM: arm64: Use page-table to track page ownership Message-ID: References: <20210315143536.214621-1-qperret@google.com> <20210315143536.214621-30-qperret@google.com> <20210315163618.GF3430@willie-the-truck> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20210315163618.GF3430@willie-the-truck> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210315_165323_213798_FB6B7FB3 X-CRM114-Status: GOOD ( 30.38 ) 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 Monday 15 Mar 2021 at 16:36:19 (+0000), Will Deacon wrote: > On Mon, Mar 15, 2021 at 02:35:29PM +0000, Quentin Perret wrote: > > As the host stage 2 will be identity mapped, all the .hyp memory regions > > and/or memory pages donated to protected guestis will have to marked > > invalid in the host stage 2 page-table. At the same time, the hypervisor > > will need a way to track the ownership of each physical page to ensure > > memory sharing or donation between entities (host, guests, hypervisor) is > > legal. > > > > In order to enable this tracking at EL2, let's use the host stage 2 > > page-table itself. The idea is to use the top bits of invalid mappings > > to store the unique identifier of the page owner. The page-table owner > > (the host) gets identifier 0 such that, at boot time, it owns the entire > > IPA space as the pgd starts zeroed. > > > > Provide kvm_pgtable_stage2_set_owner() which allows to modify the > > ownership of pages in the host stage 2. It re-uses most of the map() > > logic, but ends up creating invalid mappings instead. This impacts > > how we do refcount as we now need to count invalid mappings when they > > are used for ownership tracking. > > > > Signed-off-by: Quentin Perret > > --- > > arch/arm64/include/asm/kvm_pgtable.h | 21 +++++ > > arch/arm64/kvm/hyp/pgtable.c | 127 ++++++++++++++++++++++----- > > 2 files changed, 124 insertions(+), 24 deletions(-) > > > > diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h > > index 4ae19247837b..683e96abdc24 100644 > > --- a/arch/arm64/include/asm/kvm_pgtable.h > > +++ b/arch/arm64/include/asm/kvm_pgtable.h > > @@ -238,6 +238,27 @@ int kvm_pgtable_stage2_map(struct kvm_pgtable *pgt, u64 addr, u64 size, > > u64 phys, enum kvm_pgtable_prot prot, > > void *mc); > > > > +/** > > + * kvm_pgtable_stage2_set_owner() - Annotate invalid mappings with metadata > > + * encoding the ownership of a page in the > > + * IPA space. > > The function does more than this, though, as it will also go ahead and unmap > existing valid mappings which I think should be mentioned here, no? Right, I see why you mean. How about: 'Unmap and annotate pages in the IPA space to track ownership' > > +int kvm_pgtable_stage2_set_owner(struct kvm_pgtable *pgt, u64 addr, u64 size, > > + void *mc, u8 owner_id) > > +{ > > + int ret; > > + struct stage2_map_data map_data = { > > + .phys = KVM_PHYS_INVALID, > > + .mmu = pgt->mmu, > > + .memcache = mc, > > + .mm_ops = pgt->mm_ops, > > + .owner_id = owner_id, > > + }; > > + struct kvm_pgtable_walker walker = { > > + .cb = stage2_map_walker, > > + .flags = KVM_PGTABLE_WALK_TABLE_PRE | > > + KVM_PGTABLE_WALK_LEAF | > > + KVM_PGTABLE_WALK_TABLE_POST, > > + .arg = &map_data, > > + }; > > + > > + if (owner_id > KVM_MAX_OWNER_ID) > > + return -EINVAL; > > + > > + ret = kvm_pgtable_walk(pgt, addr, size, &walker); > > + dsb(ishst); > > Why is the DSB needed here? afaict, we only ever unmap a valid entry (which > will have a DSB as part of the TLBI sequence) or we update the owner for an > existing invalid entry, in which case the walker doesn't care. Indeed, that is now unnecessary. I'll remove it. Thanks, Quentin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel