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Tue, 23 Jun 2026 05:48:43 -0700 (PDT) X-Received: by 2002:a05:622a:1a8a:b0:516:e6f3:c1f with SMTP id d75a77b69052e-51a55b21c1amr33094631cf.47.1782218922526; Tue, 23 Jun 2026 05:48:42 -0700 (PDT) Received: from x1.com ([174.91.117.157]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-51a51106a09sm22288351cf.0.2026.06.23.05.48.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 23 Jun 2026 05:48:41 -0700 (PDT) From: Peter Xu To: qemu-devel@nongnu.org Cc: Peter Xu , Fabiano Rosas , Paolo Bonzini , =?UTF-8?q?Marc-Andr=C3=A9=20Lureau?= Subject: [PULL 15/18] system/physmem: destroy ram block attributes before RCU-deferred reclaim Date: Tue, 23 Jun 2026 08:47:56 -0400 Message-ID: <20260623124759.125399-16-peterx@redhat.com> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260623124759.125399-1-peterx@redhat.com> References: <20260623124759.125399-1-peterx@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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: -24 X-Spam_score: -2.5 X-Spam_bar: -- X-Spam_report: (-2.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.445, 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_H3=0.001, RCVD_IN_MSPIKE_WL=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: qemu development 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 From: Marc-André Lureau ram_block_attributes_destroy() was called from reclaim_ramblock(), which runs as an RCU callback deferred by call_rcu(). However,when the RamDiscardManager is finalized, it will assert that its source_list is empty in the next commit. Since the RCU callback hasn't run yet, the source added by ram_block_attributes_create() is still attached. Move ram_block_attributes_destroy() into qemu_ram_free() so the source is removed synchronously. This is safe because qemu_ram_free() during shutdown runs after pause_all_vcpus(), so no vCPU thread can concurrently access the attributes via kvm_convert_memory(). Reviewed-by: Peter Xu Signed-off-by: Marc-André Lureau Link: https://lore.kernel.org/r/20260604-rdm5-v5-8-5768e6a0943d@redhat.com [peterx: rebase on top of qemu_ram_free() change] Signed-off-by: Peter Xu --- system/physmem.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/system/physmem.c b/system/physmem.c index db8ad84ab6..c4bfb57625 100644 --- a/system/physmem.c +++ b/system/physmem.c @@ -2582,7 +2582,6 @@ static void reclaim_ramblock(RAMBlock *block) } if (block->guest_memfd >= 0) { - ram_block_attributes_destroy(block->attributes); close(block->guest_memfd); ram_block_coordinated_discard_require(false); } @@ -2610,6 +2609,7 @@ void qemu_ram_free(RAMBlock *block) qatomic_set(&ram_list.mru_block, NULL); /* Write list before version */ qatomic_store_release(&ram_list.version, ram_list.version + 1); + g_clear_pointer(&block->attributes, ram_block_attributes_destroy); call_rcu(block, reclaim_ramblock, rcu); qemu_mutex_unlock_ramlist(); } -- 2.54.0