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[2003:cb:c70d:fb00:d3ed:5f44:1b2d:12af]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-43959d3d5f3sm178381635e9.0.2025.02.18.02.46.20 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 18 Feb 2025 02:46:21 -0800 (PST) Message-ID: Date: Tue, 18 Feb 2025 11:46:17 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 2/6] memory: Change memory_region_set_ram_discard_manager() to return the result To: Alexey Kardashevskiy , Chenyi Qiang , Peter Xu , Paolo Bonzini , =?UTF-8?Q?Philippe_Mathieu-Daud=C3=A9?= , Michael Roth Cc: qemu-devel@nongnu.org, kvm@vger.kernel.org, Williams Dan J , Peng Chao P , Gao Chao , Xu Yilun , Li Xiaoyao References: <20250217081833.21568-1-chenyi.qiang@intel.com> <20250217081833.21568-3-chenyi.qiang@intel.com> <10029ca9-a239-4d3f-9999-e1059bc17d85@amd.com> From: David Hildenbrand Content-Language: en-US Autocrypt: addr=david@redhat.com; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat In-Reply-To: <10029ca9-a239-4d3f-9999-e1059bc17d85@amd.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=170.10.133.124; envelope-from=david@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_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 18.02.25 10:19, Alexey Kardashevskiy wrote: > > > On 17/2/25 19:18, Chenyi Qiang wrote: >> Modify memory_region_set_ram_discard_manager() to return false if a >> RamDiscardManager is already set in the MemoryRegion. The caller must >> handle this failure, such as having virtio-mem undo its actions and fail >> the realize() process. Opportunistically move the call earlier to avoid >> complex error handling. >> >> This change is beneficial when introducing a new RamDiscardManager >> instance besides virtio-mem. After >> ram_block_coordinated_discard_require(true) unlocks all >> RamDiscardManager instances, only one instance is allowed to be set for >> a MemoryRegion at present. >> >> Suggested-by: David Hildenbrand >> Signed-off-by: Chenyi Qiang >> --- >> Changes in v2: >> - newly added. >> --- >> hw/virtio/virtio-mem.c | 30 +++++++++++++++++------------- >> include/exec/memory.h | 6 +++--- >> system/memory.c | 11 ++++++++--- >> 3 files changed, 28 insertions(+), 19 deletions(-) >> >> diff --git a/hw/virtio/virtio-mem.c b/hw/virtio/virtio-mem.c >> index 21f16e4912..ef818a2cdf 100644 >> --- a/hw/virtio/virtio-mem.c >> +++ b/hw/virtio/virtio-mem.c >> @@ -1074,6 +1074,18 @@ static void virtio_mem_device_realize(DeviceState *dev, Error **errp) >> vmem->block_size; >> vmem->bitmap = bitmap_new(vmem->bitmap_size); >> >> + /* >> + * Set ourselves as RamDiscardManager before the plug handler maps the >> + * memory region and exposes it via an address space. >> + */ >> + if (memory_region_set_ram_discard_manager(&vmem->memdev->mr, >> + RAM_DISCARD_MANAGER(vmem))) { >> + error_setg(errp, "Failed to set RamDiscardManager"); >> + g_free(vmem->bitmap); >> + ram_block_coordinated_discard_require(false); >> + return; >> + } > > Looks like this can move before vmem->bitmap is allocated (or even > before ram_block_coordinated_discard_require(true)?). Then you can drop > g_free() and avoid having a stale pointer in vmem->bitmap (not that it > matters here though). > >> + >> virtio_init(vdev, VIRTIO_ID_MEM, sizeof(struct virtio_mem_config)); >> vmem->vq = virtio_add_queue(vdev, 128, virtio_mem_handle_request); >> vmem->bitmap >> @@ -1124,13 +1136,6 @@ static void virtio_mem_device_realize(DeviceState *dev, Error **errp) >> vmem->system_reset = VIRTIO_MEM_SYSTEM_RESET(obj); >> vmem->system_reset->vmem = vmem; >> qemu_register_resettable(obj); >> - >> - /* >> - * Set ourselves as RamDiscardManager before the plug handler maps the >> - * memory region and exposes it via an address space. >> - */ >> - memory_region_set_ram_discard_manager(&vmem->memdev->mr, >> - RAM_DISCARD_MANAGER(vmem)); >> } >> >> static void virtio_mem_device_unrealize(DeviceState *dev) >> @@ -1138,12 +1143,6 @@ static void virtio_mem_device_unrealize(DeviceState *dev) >> VirtIODevice *vdev = VIRTIO_DEVICE(dev); >> VirtIOMEM *vmem = VIRTIO_MEM(dev); >> >> - /* >> - * The unplug handler unmapped the memory region, it cannot be >> - * found via an address space anymore. Unset ourselves. >> - */ >> - memory_region_set_ram_discard_manager(&vmem->memdev->mr, NULL); >> - >> qemu_unregister_resettable(OBJECT(vmem->system_reset)); >> object_unref(OBJECT(vmem->system_reset)); >> >> @@ -1155,6 +1154,11 @@ static void virtio_mem_device_unrealize(DeviceState *dev) >> host_memory_backend_set_mapped(vmem->memdev, false); >> virtio_del_queue(vdev, 0); >> virtio_cleanup(vdev); >> + /* >> + * The unplug handler unmapped the memory region, it cannot be >> + * found via an address space anymore. Unset ourselves. >> + */ >> + memory_region_set_ram_discard_manager(&vmem->memdev->mr, NULL); >> g_free(vmem->bitmap); >> ram_block_coordinated_discard_require(false); >> } >> diff --git a/include/exec/memory.h b/include/exec/memory.h >> index 3bebc43d59..390477b588 100644 >> --- a/include/exec/memory.h >> +++ b/include/exec/memory.h >> @@ -2487,13 +2487,13 @@ static inline bool memory_region_has_ram_discard_manager(MemoryRegion *mr) >> * >> * This function must not be called for a mapped #MemoryRegion, a #MemoryRegion >> * that does not cover RAM, or a #MemoryRegion that already has a >> - * #RamDiscardManager assigned. >> + * #RamDiscardManager assigned. Return 0 if the rdm is set successfully. >> * >> * @mr: the #MemoryRegion >> * @rdm: #RamDiscardManager to set >> */ >> -void memory_region_set_ram_discard_manager(MemoryRegion *mr, >> - RamDiscardManager *rdm); >> +int memory_region_set_ram_discard_manager(MemoryRegion *mr, >> + RamDiscardManager *rdm); >> >> /** >> * memory_region_find: translate an address/size relative to a >> diff --git a/system/memory.c b/system/memory.c >> index b17b5538ff..297a3dbcd4 100644 >> --- a/system/memory.c >> +++ b/system/memory.c >> @@ -2115,12 +2115,17 @@ RamDiscardManager *memory_region_get_ram_discard_manager(MemoryRegion *mr) >> return mr->rdm; >> } >> >> -void memory_region_set_ram_discard_manager(MemoryRegion *mr, >> - RamDiscardManager *rdm) >> +int memory_region_set_ram_discard_manager(MemoryRegion *mr, >> + RamDiscardManager *rdm) >> { >> g_assert(memory_region_is_ram(mr)); >> - g_assert(!rdm || !mr->rdm); >> + if (mr->rdm && rdm != NULL) { > > Drop "!= NULL". > >> + return -1; > > -EBUSY? > >> + } >> + >> + /* !rdm || !mr->rdm */ > > See, like here - no "!= NULL" :) (and the comment is useless). Thanks, > > >> mr->rdm = rdm; >> + return 0; >> } >> >> uint64_t ram_discard_manager_get_min_granularity(const RamDiscardManager *rdm, > Agreed to all, with that it LGTM, thanks! -- Cheers, David / dhildenb