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[2003:cb:c71a:3000:973c:c367:3012:8b20]) by smtp.gmail.com with ESMTPSA id d2-20020a5d6dc2000000b00317f70240afsm5881819wrz.27.2023.08.11.09.25.14 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 11 Aug 2023 09:25:15 -0700 (PDT) Message-ID: Date: Fri, 11 Aug 2023 18:25:14 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.13.0 Subject: Re: [PATCH v1 1/3] softmmu/physmem: fallback to opening guest RAM file as readonly in a MAP_PRIVATE mapping Content-Language: en-US To: Peter Xu Cc: ThinerLogoer , qemu-devel@nongnu.org, Paolo Bonzini , Igor Mammedov , =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= References: <1d1a7d8f-6260-5905-57ea-514b762ce869@redhat.com> <6152f171.6a4c.189e069baf7.Coremail.logoerthiner1@163.com> <9feaf960-637b-9392-3c8f-9e1ba1a7ca40@redhat.com> <996a69ff-e2dc-0ed0-2ac8-33fd53bd02c2@redhat.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=170.10.129.124; envelope-from=david@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.972, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 11.08.23 18:22, Peter Xu wrote: > On Fri, Aug 11, 2023 at 06:17:05PM +0200, David Hildenbrand wrote: >> We wouldn't touch "-mem-path". > > But still the same issue when someone uses -object memory-backend-file for > hugetlb, mapping privately, expecting ram discard to work? > > Basically I see that example as, "hugetlb" in general made the private > mapping over RW file usable, so forbidden that anywhere may take a risk. These users can be directed to using hugetlb a) using MAP_SHARED b) using memory-backend-memfd, if MAP_PRIVATE is desired Am I missing any important use case? Are we being a bit to careful about virtio-balloon and postcopy simply not being available for these corner cases? -- Cheers, David / dhildenb