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Fri, 02 Jan 2026 05:09:25 -0800 (PST) X-Google-Smtp-Source: AGHT+IGVx2v2dwu0fIzSvqndlwMz4UEgI5xmWAJWQkyrEO26qgF9MWsaKkBLaC1Sq3yurRK0AjpEcQ== X-Received: by 2002:a17:907:944d:b0:b83:51e0:120 with SMTP id a640c23a62f3a-b8351e005e2mr1859482466b.65.1767359365450; Fri, 02 Jan 2026 05:09:25 -0800 (PST) Received: from imammedo-mac ([185.140.112.229]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-b8037de1421sm4632545266b.41.2026.01.02.05.09.24 (version=TLS1_2 cipher=AES128-SHA bits=128/128); Fri, 02 Jan 2026 05:09:25 -0800 (PST) Date: Fri, 2 Jan 2026 14:09:22 +0100 From: Igor Mammedov To: fanhuang Cc: , , , , Subject: Re: [PATCH v4 0/1] numa: add 'spm' option for Specific Purpose Memory Message-ID: <20260102140922.456f599e@imammedo-mac> In-Reply-To: <20251209093841.2250527-1-FangSheng.Huang@amd.com> References: <20251209093841.2250527-1-FangSheng.Huang@amd.com> Organization: imammedo@redhat.com X-Mailer: Claws Mail 3.11.1-67-g0d58c6-dirty (GTK+ 2.24.21; x86_64-apple-darwin14.0.0) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=170.10.129.124; envelope-from=imammedo@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_H2=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_PASS=-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 Tue, 9 Dec 2025 17:38:40 +0800 fanhuang wrote: > Hi all, > > This is v4 of the SPM (Specific Purpose Memory) patch. Thank you Jonathan > for the detailed review. > > Changes in v4 (addressing Jonathan's feedback): > - Added architecture check: spm=on now reports error on non-x86 machines > - Simplified return logic in e820_update_entry_type() (return true/false directly) > - Changed 4GB boundary spanning from warn_report to error_report + exit > - Updated QAPI documentation to be architecture-agnostic (removed E820 reference) > - Removed unnecessary comments > > Use case: > This feature allows passing EFI_MEMORY_SP (Specific Purpose Memory) from > host to guest VM, useful for memory reserved for specific PCI devices > (e.g., GPU memory via VFIO-PCI). The SPM memory appears as soft reserved > to the guest and is managed by device drivers rather than the OS memory > allocator. > > Example usage: > -object memory-backend-ram,size=8G,id=m0 > -object memory-backend-file,size=8G,id=m1,mem-path=/dev/dax0.0 > -numa node,nodeid=0,memdev=m0 > -numa node,nodeid=1,memdev=m1,spm=on I'm still not fond of 'spm' toggle on numa node itself (even though on AMD hadware sunch memory has 1:1 mapping) without device model in between. Can we try following instead: * add 'spm' property to DIMM device and disable hotplug on it in such case * make E820 enumerate spm/not hotpluggble marked DIMMs. That will let us later to have mixed memory on the node if such need arises without breaking QEMU CLI. > Please review. Thanks! > > Best regards, > Jerry Huang >