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[34.91.112.229]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-abf0c1165e7sm333069566b.82.2025.02.28.11.06.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 28 Feb 2025 11:06:50 -0800 (PST) Date: Fri, 28 Feb 2025 19:06:46 +0000 From: Quentin Perret To: Vincent Donnefort Cc: maz@kernel.org, oliver.upton@linux.dev, joey.gouly@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, catalin.marinas@arm.com, will@kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-kernel@vger.kernel.org, kernel-team@android.com Subject: Re: [PATCH 2/9] KVM: arm64: Add a range to __pkvm_host_share_guest() Message-ID: References: <20250228102530.1229089-1-vdonnefort@google.com> <20250228102530.1229089-3-vdonnefort@google.com> Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250228102530.1229089-3-vdonnefort@google.com> On Friday 28 Feb 2025 at 10:25:18 (+0000), Vincent Donnefort wrote: > +int __pkvm_host_share_guest(u64 pfn, u64 gfn, u64 nr_pages, struct pkvm_hyp_vcpu *vcpu, > enum kvm_pgtable_prot prot) > { > struct pkvm_hyp_vm *vm = pkvm_hyp_vcpu_to_hyp_vm(vcpu); > u64 phys = hyp_pfn_to_phys(pfn); > u64 ipa = hyp_pfn_to_phys(gfn); > struct hyp_page *page; > + u64 size; > int ret; > > if (prot & ~KVM_PGTABLE_PROT_RWX) > return -EINVAL; > > - ret = check_range_allowed_memory(phys, phys + PAGE_SIZE); I'm not sure it is safe to drop this check here, see below. > + ret = __guest_check_transition_size(phys, ipa, nr_pages, &size); > if (ret) > return ret; > > host_lock_component(); > guest_lock_component(vm); > > - ret = __guest_check_page_state_range(vcpu, ipa, PAGE_SIZE, PKVM_NOPAGE); > + ret = __guest_check_page_state_range(vm, ipa, size, PKVM_NOPAGE); > if (ret) > goto unlock; > > page = hyp_phys_to_page(phys); Phys really needs to be a valid memory address here for 'page' to be present in the vmemma -- dereference right below. So we can't rely on the check in __host_check_page_state_range() sadly ... > + ret = __host_check_page_state_range(phys, size, page->host_state); > + if (ret) > + goto unlock; > + > switch (page->host_state) { > case PKVM_PAGE_OWNED: > - WARN_ON(__host_set_page_state_range(phys, PAGE_SIZE, PKVM_PAGE_SHARED_OWNED)); > + WARN_ON(__host_set_page_state_range(phys, size, PKVM_PAGE_SHARED_OWNED)); > break; > case PKVM_PAGE_SHARED_OWNED: > - if (page->host_share_guest_count) > - break; > - /* Only host to np-guest multi-sharing is tolerated */ > - WARN_ON(1); > - fallthrough; > + for_each_hyp_page(phys, size, page) { > + /* Only host to np-guest multi-sharing is tolerated */ > + if (WARN_ON(!page->host_share_guest_count)) { > + ret = -EPERM; > + goto unlock; > + } > + } > + break; > default: > ret = -EPERM; > goto unlock; > } > > - WARN_ON(kvm_pgtable_stage2_map(&vm->pgt, ipa, PAGE_SIZE, phys, > + WARN_ON(kvm_pgtable_stage2_map(&vm->pgt, ipa, size, phys, > pkvm_mkstate(prot, PKVM_PAGE_SHARED_BORROWED), > &vcpu->vcpu.arch.pkvm_memcache, 0)); > - page->host_share_guest_count++; > + __host_update_share_guest_count(phys, size, true); > > unlock: > guest_unlock_component(vm); > diff --git a/arch/arm64/kvm/pkvm.c b/arch/arm64/kvm/pkvm.c > index 930b677eb9b0..00fd9a524bf7 100644 > --- a/arch/arm64/kvm/pkvm.c > +++ b/arch/arm64/kvm/pkvm.c > @@ -361,7 +361,7 @@ int pkvm_pgtable_stage2_map(struct kvm_pgtable *pgt, u64 addr, u64 size, > return -EINVAL; > > lockdep_assert_held_write(&kvm->mmu_lock); > - ret = kvm_call_hyp_nvhe(__pkvm_host_share_guest, pfn, gfn, prot); > + ret = kvm_call_hyp_nvhe(__pkvm_host_share_guest, pfn, gfn, 1, prot); > if (ret) { > /* Is the gfn already mapped due to a racing vCPU? */ > if (ret == -EPERM) > -- > 2.48.1.711.g2feabab25a-goog >