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Tue, 20 Jul 2021 08:49:48 -0700 (PDT) Date: Tue, 20 Jul 2021 16:49:45 +0100 From: Quentin Perret To: Marc Zyngier 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 04/16] KVM: arm64: Add MMIO checking infrastructure Message-ID: References: <20210715163159.1480168-1-maz@kernel.org> <20210715163159.1480168-5-maz@kernel.org> <87wnpl86sz.wl-maz@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87wnpl86sz.wl-maz@kernel.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tuesday 20 Jul 2021 at 14:15:56 (+0100), Marc Zyngier wrote: > On Tue, 20 Jul 2021 12:13:20 +0100, > Quentin Perret wrote: > > > > On Thursday 15 Jul 2021 at 17:31:47 (+0100), Marc Zyngier wrote: > > > +struct s2_walk_data { > > > + kvm_pte_t pteval; > > > + u32 level; > > > +}; > > > + > > > +static int s2_walker(u64 addr, u64 end, u32 level, kvm_pte_t *ptep, > > > + enum kvm_pgtable_walk_flags flag, void * const arg) > > > +{ > > > + struct s2_walk_data *data = arg; > > > + > > > + data->level = level; > > > + data->pteval = *ptep; > > > + return 0; > > > +} > > > + > > > +/* Assumes mmu_lock taken */ > > > +static bool __check_ioguard_page(struct kvm_vcpu *vcpu, gpa_t ipa) > > > +{ > > > + struct s2_walk_data data; > > > + struct kvm_pgtable_walker walker = { > > > + .cb = s2_walker, > > > + .flags = KVM_PGTABLE_WALK_LEAF, > > > + .arg = &data, > > > + }; > > > + > > > + kvm_pgtable_walk(vcpu->arch.hw_mmu->pgt, ALIGN_DOWN(ipa, PAGE_SIZE), > > > + PAGE_SIZE, &walker); > > > + > > > + /* Must be a PAGE_SIZE mapping with our annotation */ > > > + return (BIT(ARM64_HW_PGTABLE_LEVEL_SHIFT(data.level)) == PAGE_SIZE && > > > + data.pteval == MMIO_NOTE); > > > > Nit: you could do this check in the walker directly and check the return > > value of kvm_pgtable_walk() instead. That would allow to get rid of > > struct s2_walk_data. > > > > Also, though the compiler might be able to optimize, maybe simplify the > > level check to level == (KVM_PGTABLE_MAX_LEVELS - 1)? > > Yup, all good points. I guess I could do the same in my other series > that parses the userspace PT to extract the level. Well, actually, let me take that back. I think something like you have would be useful, but in pgtable.c directly and re-usable for stage-1 and stage-2 walks. Maybe something like the below (totally untested)? I could use such a walker in several places as well in the memory ownership series: - following the idea of [1], I could remove the kvm_pgtable_stage2_find_range() function entirely; - [2] defines 2 custom walkers that do nothing but walk host stage-2 and hyp stage-1 page-tables to check permissions and such -- they could be removed/re-implemented easily as well. And you seem to need something similar here, so clearly there is a need. WDYT? Thanks, Quentin [1] https://lore.kernel.org/kvmarm/20210719104735.3681732-3-qperret@google.com/ [2] https://lore.kernel.org/kvmarm/20210719104735.3681732-14-qperret@google.com/ diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c index e0ae57dca827..bd6d26f27e1a 100644 --- a/arch/arm64/kvm/hyp/pgtable.c +++ b/arch/arm64/kvm/hyp/pgtable.c @@ -357,6 +357,38 @@ int kvm_pgtable_walk(struct kvm_pgtable *pgt, u64 addr, u64 size, return _kvm_pgtable_walk(&walk_data); } +struct get_leaf_data { + kvm_pte_t *ptep; + u32 *level; +}; + +static int get_leaf_walker(u64 addr, u64 end, u32 level, kvm_pte_t *ptep, + enum kvm_pgtable_walk_flags flag, void * const arg) +{ + struct get_leaf_data *data = arg; + + *(data->ptep) = *ptep; + *(data->level) = level; + + return 0; +} + +int kvm_pgtable_get_leaf(struct kvm_pgtable *pgt, u64 addr, kvm_pte_t *ptep, + u32 *level) +{ + struct get_leaf_data data = { + .ptep = ptep, + .level = level, + }; + struct kvm_pgtable_walker __get_leaf_walker = { + .cb = get_leaf_walker, + .flags = KVM_PGTABLE_WALK_LEAF, + .arg = &data, + }; + + return kvm_pgtable_walk(pgt, addr, PAGE_SIZE, &__get_leaf_walker); +} + struct hyp_map_data { u64 phys; kvm_pte_t attr;