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[99.254.114.190]) by smtp.gmail.com with ESMTPSA id af79cd13be357-7be614d9af2sm482989285a.77.2025.01.20.12.46.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 20 Jan 2025 12:46:17 -0800 (PST) Date: Mon, 20 Jan 2025 15:46:15 -0500 From: Peter Xu To: Alexey Kardashevskiy Cc: Chenyi Qiang , David Hildenbrand , Paolo Bonzini , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , Michael Roth , qemu-devel@nongnu.org, kvm@vger.kernel.org, Williams Dan J , Peng Chao P , Gao Chao , Xu Yilun Subject: Re: [PATCH 2/7] guest_memfd: Introduce an object to manage the guest-memfd with RamDiscardManager Message-ID: References: <80ac1338-a116-48f5-9874-72d42b5b65b4@intel.com> <219a4a7a-7c96-4746-9aba-ed06a1a00f3e@amd.com> <58b96b74-bf9c-45d3-8c2e-459ec2206fc8@intel.com> <8c8e024d-03dc-4201-8038-9e9e60467fad@amd.com> <4d22d3ce-a5a1-49f2-a578-8e0fe7d26893@amd.com> <2b799426-deaa-4644-aa17-6ef31899113b@intel.com> <2400268e-d26a-4933-80df-cfe44b38ae40@amd.com> <590432e1-4a26-4ae8-822f-ccfbac352e6b@intel.com> <2b2730f3-6e1a-4def-b126-078cf6249759@amd.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <2b2730f3-6e1a-4def-b126-078cf6249759@amd.com> On Mon, Jan 20, 2025 at 09:22:50PM +1100, Alexey Kardashevskiy wrote: > > It is still uncertain how to implement the private MMIO. Our assumption > > is the private MMIO would also create a memory region with > > guest_memfd-like backend. Its mr->ram is true and should be managed by > > RamdDiscardManager which can skip doing DMA_MAP in VFIO's region_add > > listener. > > My current working approach is to leave it as is in QEMU and VFIO. Agreed. Setting ram=true to even private MMIO sounds hackish, at least currently QEMU heavily rely on that flag for any possible direct accesses. E.g., in memory_access_is_direct(). -- Peter Xu