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[99.254.144.39]) by smtp.gmail.com with ESMTPSA id g20-20020a0cdf14000000b0063d585225e0sm740577qvl.61.2023.08.10.14.24.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 10 Aug 2023 14:24:44 -0700 (PDT) Date: Thu, 10 Aug 2023 17:24:43 -0400 From: Peter Xu To: ThinerLogoer Cc: David Hildenbrand , qemu-devel@nongnu.org, Paolo Bonzini , Igor Mammedov , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= Subject: Re: Re: [PATCH v1 1/3] softmmu/physmem: fallback to opening guest RAM file as readonly in a MAP_PRIVATE mapping Message-ID: References: <20230807190736.572665-1-david@redhat.com> <20230807190736.572665-2-david@redhat.com> <1d1a7d8f-6260-5905-57ea-514b762ce869@redhat.com> <6152f171.6a4c.189e069baf7.Coremail.logoerthiner1@163.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <6152f171.6a4c.189e069baf7.Coremail.logoerthiner1@163.com> Received-SPF: pass client-ip=170.10.129.124; envelope-from=peterx@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 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, 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 Fri, Aug 11, 2023 at 01:06:12AM +0800, ThinerLogoer wrote: > >I think we have the following options (there might be more) > > > >1) This patch. > > > >2) New flag for memory-backend-file. We already have "readonly" and > >"share=". I'm having a hard time coming up with a good name that really > >describes the subtle difference. > > > >3) Glue behavior to the QEMU machine > > > > 4) '-deny-private-discard' argv, or environment variable, or both I'd personally vote for (2). How about "fdperm"? To describe when we want to use different rw permissions on the file (besides the access permission of the memory we already provided with "readonly"=XXX). IIUC the only sane value will be ro/rw/default, where "default" should just use the same rw permission as the memory ("readonly"=XXX). Would that be relatively clean and also work in this use case? (the other thing I'd wish we don't have that fallback is, as long as we have any of that "fallback" we'll need to be compatible with it since then, and for ever...) -- Peter Xu