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From: Oliver Upton To: Catalin Marinas Cc: ankita@nvidia.com, jgg@nvidia.com, maz@kernel.org, james.morse@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, reinette.chatre@intel.com, surenb@google.com, stefanha@redhat.com, brauner@kernel.org, will@kernel.org, mark.rutland@arm.com, alex.williamson@redhat.com, kevin.tian@intel.com, yi.l.liu@intel.com, ardb@kernel.org, akpm@linux-foundation.org, andreyknvl@gmail.com, wangjinchao@xfusion.com, gshan@redhat.com, ricarkol@google.com, linux-mm@kvack.org, lpieralisi@kernel.org, rananta@google.com, ryan.roberts@arm.com, aniketa@nvidia.com, cjia@nvidia.com, kwankhede@nvidia.com, targupta@nvidia.com, vsethi@nvidia.com, acurrid@nvidia.com, apopple@nvidia.com, jhubbard@nvidia.com, danw@nvidia.com, kvmarm@lists.linux.dev, mochs@nvidia.com, zhiw@nvidia.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v6 1/4] kvm: arm64: introduce new flag for non-cacheable IO memory Message-ID: References: <20240207204652.22954-1-ankita@nvidia.com> <20240207204652.22954-2-ankita@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 03BE8140003 X-Stat-Signature: 6abbtqu781sjb61ahc6rhw7w1tpa994w X-Rspam-User: X-HE-Tag: 1707398706-664875 X-HE-Meta: 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 DD1AyHzy yScZgIrm0LCv0MUeob3LoNq85OUeJQvCtjPFKqMTMsSZfTiRg9H7pn3ebYsBbzm9EM8jsHsoSLRafugW5aibroQIP1GqyvkbuufLc2hHzCwtDzGPIu154JWyoqw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Feb 08, 2024 at 01:00:59PM +0000, Catalin Marinas wrote: > On Thu, Feb 08, 2024 at 02:16:49AM +0530, ankita@nvidia.com wrote: > > diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c > > index c651df904fe3..2a893724ee9b 100644 > > --- a/arch/arm64/kvm/hyp/pgtable.c > > +++ b/arch/arm64/kvm/hyp/pgtable.c > > @@ -717,15 +717,28 @@ void kvm_tlb_flush_vmid_range(struct kvm_s2_mmu *mmu, > > static int stage2_set_prot_attr(struct kvm_pgtable *pgt, enum kvm_pgtable_prot prot, > > kvm_pte_t *ptep) > > { > > - bool device = prot & KVM_PGTABLE_PROT_DEVICE; > > - kvm_pte_t attr = device ? KVM_S2_MEMATTR(pgt, DEVICE_nGnRE) : > > - KVM_S2_MEMATTR(pgt, NORMAL); > > + kvm_pte_t attr; > > u32 sh = KVM_PTE_LEAF_ATTR_LO_S2_SH_IS; > > > > + switch (prot & (KVM_PGTABLE_PROT_DEVICE | > > + KVM_PGTABLE_PROT_NORMAL_NC)) { > > + case 0: > > + attr = KVM_S2_MEMATTR(pgt, NORMAL); > > + break; > > + case KVM_PGTABLE_PROT_DEVICE: > > + if (prot & KVM_PGTABLE_PROT_X) > > + return -EINVAL; > > + attr = KVM_S2_MEMATTR(pgt, DEVICE_nGnRE); > > + break; > > + case KVM_PGTABLE_PROT_NORMAL_NC: > > + attr = KVM_S2_MEMATTR(pgt, NORMAL_NC); > > + break; > > Does it make sense to allow executable here as well? I don't think it's > harmful but not sure there's a use-case for it either. Ah, we should just return EINVAL for that too. I get that the memory attribute itself is not problematic, but since we're only using this thing for MMIO it'd be a rather massive bug in KVM... We reject attempts to do this earlier in user_mem_abort(). If, for some reason, we wanted to do Normal-NC actual memory then we would need to make sure that KVM does the appropriate cache maintenance at map / unmap. -- Thanks, Oliver