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[34.34.157.35]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-ac7c0184d0dsm280758066b.130.2025.04.04.10.05.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 04 Apr 2025 10:05:32 -0700 (PDT) Date: Fri, 4 Apr 2025 18:05:28 +0100 From: Vincent Donnefort To: Quentin Perret 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 v2 3/9] KVM: arm64: Add a range to __pkvm_host_unshare_guest() Message-ID: References: <20250306110038.3733649-1-vdonnefort@google.com> <20250306110038.3733649-4-vdonnefort@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250404_100534_840657_71A86A89 X-CRM114-Status: GOOD ( 16.53 ) 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: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Apr 03, 2025 at 03:31:47PM +0000, Quentin Perret wrote: > On Thursday 06 Mar 2025 at 11:00:32 (+0000), Vincent Donnefort wrote: > > @@ -1012,51 +1011,52 @@ static int __check_host_shared_guest(struct pkvm_hyp_vm *vm, u64 *__phys, u64 ip > > return ret; > > if (!kvm_pte_valid(pte)) > > return -ENOENT; > > - if (level != KVM_PGTABLE_LAST_LEVEL) > > + if (kvm_granule_size(level) != size) > > return -E2BIG; > > > > - state = guest_get_page_state(pte, ipa); > > - if (state != PKVM_PAGE_SHARED_BORROWED) > > - return -EPERM; > > + ret = __guest_check_page_state_range(vm, ipa, size, PKVM_PAGE_SHARED_BORROWED); > > + if (ret) > > + return ret; > > Given that hard rely on kvm_granule_size(level) == size above, we should > be guaranteed that the PTE covers the entire range we're interested in. > So is there a point in starting a new page-table walk here? Could we > just keep guest_get_page_state() directly? Ha yes, the walk wouldn't do anything more than what we can with that PTE! > > > > > phys = kvm_pte_to_phys(pte); > > - ret = check_range_allowed_memory(phys, phys + PAGE_SIZE); > > + ret = check_range_allowed_memory(phys, phys + size); > > if (WARN_ON(ret)) > > return ret; > > > > - page = hyp_phys_to_page(phys); > > - if (page->host_state != PKVM_PAGE_SHARED_OWNED) > > - return -EPERM; > > - if (WARN_ON(!page->host_share_guest_count)) > > - return -EINVAL; > > + for_each_hyp_page(phys, size, page) { > > + if (page->host_state != PKVM_PAGE_SHARED_OWNED) > > + return -EPERM; > > + if (WARN_ON(!page->host_share_guest_count)) > > + return -EINVAL; > > + } > > > > *__phys = phys; > > > > return 0; > > }