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[174.89.135.171]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-70729acdb93sm66604516d6.44.2025.07.30.14.47.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 30 Jul 2025 14:47:56 -0700 (PDT) Date: Wed, 30 Jul 2025 17:47:52 -0400 From: Peter Xu To: Igor Mammedov Cc: qemu-devel@nongnu.org, pbonzini@redhat.com, mst@redhat.com, mtosatti@redhat.com, kraxel@redhat.com, peter.maydell@linaro.org Subject: Re: [PATCH v2 1/6] memory: reintroduce BQL-free fine-grained PIO/MMIO Message-ID: References: <20250730123934.1787379-1-imammedo@redhat.com> <20250730123934.1787379-2-imammedo@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20250730123934.1787379-2-imammedo@redhat.com> Received-SPF: pass client-ip=170.10.133.124; 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_H5=0.001, RCVD_IN_MSPIKE_WL=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 Wed, Jul 30, 2025 at 02:39:29PM +0200, Igor Mammedov wrote: > diff --git a/system/memory.c b/system/memory.c > index 5646547940..9a5a262112 100644 > --- a/system/memory.c > +++ b/system/memory.c > @@ -2546,6 +2546,12 @@ void memory_region_clear_flush_coalesced(MemoryRegion *mr) > } > } > > +void memory_region_enable_lockless_io(MemoryRegion *mr) > +{ > + mr->lockless_io = true; > + mr->disable_reentrancy_guard = true; IIUC this is needed only because the re-entrancy guard is not per-transaction but per-device, am I right? Maybe some comment would be nice here to explain how mmio concurrency could affect this. If my above comment is correct, it could also be a TODO so we could re-enable this when it is per-transaction (even though I don't know whether it's easy / useful to do..). Thanks, -- Peter Xu