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Thu, 6 Feb 2020 10:55:50 +0000 (UTC) Received: from [10.36.118.119] (unknown [10.36.118.119]) by smtp.corp.redhat.com (Postfix) with ESMTP id 764205C1D8; Thu, 6 Feb 2020 10:55:40 +0000 (UTC) Subject: Re: [PATCH v2 1/7] exec: Fix for qemu_ram_resize() callback To: Shameerali Kolothum Thodi , Igor Mammedov References: <20200117174522.22044-1-shameerali.kolothum.thodi@huawei.com> <20200117174522.22044-2-shameerali.kolothum.thodi@huawei.com> <20200204162320.67e5d353@redhat.com> <74eaaa45-0d20-9a21-fbf8-6d29deb248eb@redhat.com> <4ce41554-8b8e-dbb5-5fe9-43af09950f23@redhat.com> <8e0b2c762e914c64bebfab5fc7441661@huawei.com> <133f274e-e942-7008-93d2-8edb1bc4d7ae@redhat.com> <52fff289cca14874ad493fc25806fe3d@huawei.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; prefer-encrypt=mutual; keydata= mQINBFXLn5EBEAC+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 B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABtCREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT6JAlgEEwEIAEICGwMFCQlmAYAGCwkIBwMCBhUI AgkKCwQWAgMBAh4BAheAFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl3pImkCGQEACgkQTd4Q 9wD/g1o+VA//SFvIHUAvul05u6wKv/pIR6aICPdpF9EIgEU448g+7FfDgQwcEny1pbEzAmiw zAXIQ9H0NZh96lcq+yDLtONnXk/bEYWHHUA014A1wqcYNRY8RvY1+eVHb0uu0KYQoXkzvu+s Dncuguk470XPnscL27hs8PgOP6QjG4jt75K2LfZ0eAqTOUCZTJxA8A7E9+XTYuU0hs7QVrWJ jQdFxQbRMrYz7uP8KmTK9/Cnvqehgl4EzyRaZppshruKMeyheBgvgJd5On1wWq4ZUV5PFM4x II3QbD3EJfWbaJMR55jI9dMFa+vK7MFz3rhWOkEx/QR959lfdRSTXdxs8V3zDvChcmRVGN8U Vo93d1YNtWnA9w6oCW1dnDZ4kgQZZSBIjp6iHcA08apzh7DPi08jL7M9UQByeYGr8KuR4i6e RZI6xhlZerUScVzn35ONwOC91VdYiQgjemiVLq1WDDZ3B7DIzUZ4RQTOaIWdtXBWb8zWakt/ ztGhsx0e39Gvt3391O1PgcA7ilhvqrBPemJrlb9xSPPRbaNAW39P8ws/UJnzSJqnHMVxbRZC Am4add/SM+OCP0w3xYss1jy9T+XdZa0lhUvJfLy7tNcjVG/sxkBXOaSC24MFPuwnoC9WvCVQ ZBxouph3kqc4Dt5X1EeXVLeba+466P1fe1rC8MbcwDkoUo65Ag0EVcufkQEQAOfX3n0g0fZz 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+w6DABEBAAGJAiUEGAECAA8FAlXLn5ECGwwFCQlmAYAACgkQTd4Q 9wD/g1qA6w/+M+ggFv+JdVsz5+ZIc6MSyGUozASX+bmIuPeIecc9UsFRatc91LuJCKMkD9Uv GOcWSeFpLrSGRQ1Z7EMzFVU//qVs6uzhsNk0RYMyS0B6oloW3FpyQ+zOVylFWQCzoyyf227y GW8HnXunJSC+4PtlL2AY4yZjAVAPLK2l6mhgClVXTQ/S7cBoTQKP+jvVJOoYkpnFxWE9pn4t H5QIFk7Ip8TKr5k3fXVWk4lnUi9MTF/5L/mWqdyIO1s7cjharQCstfWCzWrVeVctpVoDfJWp 4LwTuQ5yEM2KcPeElLg5fR7WB2zH97oI6/Ko2DlovmfQqXh9xWozQt0iGy5tWzh6I0JrlcxJ ileZWLccC4XKD1037Hy2FLAjzfoWgwBLA6ULu0exOOdIa58H4PsXtkFPrUF980EEibUp0zFz GotRVekFAceUaRvAj7dh76cToeZkfsjAvBVb4COXuhgX6N4pofgNkW2AtgYu1nUsPAo+NftU CxrhjHtLn4QEBpkbErnXQyMjHpIatlYGutVMS91XTQXYydCh5crMPs7hYVsvnmGHIaB9ZMfB njnuI31KBiLUks+paRkHQlFcgS2N3gkRBzH7xSZ+t7Re3jvXdXEzKBbQ+dC3lpJB0wPnyMcX FOTT3aZT7IgePkt5iC/BKBk3hqKteTnJFeVIT7EC+a6YUFg= Organization: Red Hat GmbH Message-ID: Date: Thu, 6 Feb 2020 11:55:39 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.3.1 MIME-Version: 1.0 In-Reply-To: <52fff289cca14874ad493fc25806fe3d@huawei.com> Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-MC-Unique: kS86Aa1GOAKvT8Kl-kdQ9g-1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 207.211.31.81 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "peter.maydell@linaro.org" , "xiaoguangrong.eric@gmail.com" , "mst@redhat.com" , "qemu-devel@nongnu.org" , Linuxarm , "shannon.zhaosl@gmail.com" , "qemu-arm@nongnu.org" , "xuwei \(O\)" , "lersek@redhat.com" , "eric.auger@redhat.com" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 06.02.20 11:20, Shameerali Kolothum Thodi wrote: >=20 >=20 >> -----Original Message----- >> From: David Hildenbrand [mailto:david@redhat.com] >> Sent: 05 February 2020 16:41 >> To: Shameerali Kolothum Thodi ; >> Igor Mammedov >> Cc: peter.maydell@linaro.org; xiaoguangrong.eric@gmail.com; >> mst@redhat.com; shannon.zhaosl@gmail.com; qemu-devel@nongnu.org; >> xuwei (O) ; Linuxarm ; >> eric.auger@redhat.com; qemu-arm@nongnu.org; lersek@redhat.com >> Subject: Re: [PATCH v2 1/7] exec: Fix for qemu_ram_resize() callback >> >>>> Oh, and one more reason why the proposal in this patch is inconsistent= : >>>> >>>> When migrating resizable memory regions (RAM_SAVE_FLAG_MEM_SIZE) >> we >>>> store the block->used_length (ram_save_setup()) and use that value to >>>> resize the region on the target (ram_load_precopy() -> qemu_ram_resize= ()). >>>> >>>> This will be the value the callback will be called with. Page aligned. >>>> >>> >>> Sorry, I didn=E2=80=99t quite get that point and not sure how "req_leng= th" approach >>> will affect the migration. >> >> The issue is that on migration, you will lose the sub-page size either >> way. So your callback will be called >> - on the migration source with a sub-page size (via >> memory_region_ram_resize() from e.g., hw/i386/acpi-build.c) >> - on the migration target with a page-aligned size (via >> qemu_ram_resize() from migration/ram.c) >> >> So this is inconsistent, especially when migrating. >=20 > Thanks for explaining. I tried to add some debug prints to further unders= tand > what actually happens during migration case. >=20 > Guest-source with initial one nvdimm > ---------------------------------------------------- >=20 > -object memory-backend-ram,id=3Dmem1,size=3D1G \ > -device nvdimm,id=3Ddimm1,memdev=3Dmem1 \ >=20 > fw_cfg_add_file_callback: filename etc/boot-fail-wait size 0x4 > fw_cfg_add_file_callback: filename etc/acpi/nvdimm-mem size 0x1000 > fw_cfg_add_file_callback: filename etc/acpi/tables size 0x55f4 > fw_cfg_add_file_callback: filename etc/table-loader size 0xd00 > fw_cfg_add_file_callback: filename etc/tpm/log size 0x0 > fw_cfg_add_file_callback: filename etc/acpi/rsdp size 0x24 > fw_cfg_add_file_callback: filename etc/smbios/smbios-tables size 0x104 > fw_cfg_add_file_callback: filename etc/smbios/smbios-anchor size 0x18 > fw_cfg_modify_file: filename bootorder len 0x0 > fw_cfg_add_file_callback: filename bootorder size 0x0 > fw_cfg_modify_file: filename bios-geometry len 0x0 > fw_cfg_add_file_callback: filename bios-geometry size 0x0 > fw_cfg_modify_file: filename etc/acpi/tables len 0x55f4 > fw_cfg_modify_file: filename etc/acpi/rsdp len 0x24 > fw_cfg_modify_file: filename etc/table-loader len 0xd00 > .... >=20 > hot add another nvdimm device, >=20 > (qemu) object_add memory-backend-ram,id=3Dmem2,size=3D1G > (qemu) device_add nvdimm,id=3Ddimm2,memdev=3Dmem2 >=20 >=20 > root@ubuntu:/# cat /dev/pmem > pmem0 pmem1 >=20 > Guest-target with two nvdimms > ----------------------------------------------- >=20 > -object memory-backend-ram,id=3Dmem1,size=3D1G \ > -device nvdimm,id=3Ddimm1,memdev=3Dmem1 \ > -object memory-backend-ram,id=3Dmem2,size=3D1G \ > -device nvdimm,id=3Ddimm2,memdev=3Dmem2 \ >=20 > fw_cfg_add_file_callback: filename etc/boot-fail-wait size 0x4 > fw_cfg_add_file_callback: filename etc/acpi/nvdimm-mem size 0x1000 > fw_cfg_add_file_callback: filename etc/acpi/tables size 0x56ac > fw_cfg_add_file_callback: filename etc/table-loader size 0xd00 > fw_cfg_add_file_callback: filename etc/tpm/log size 0x0 > fw_cfg_add_file_callback: filename etc/acpi/rsdp size 0x24 > fw_cfg_add_file_callback: filename etc/smbios/smbios-tables size 0x104 > fw_cfg_add_file_callback: filename etc/smbios/smbios-anchor size 0x18 > fw_cfg_modify_file: filename bootorder len 0x0 > fw_cfg_add_file_callback: filename bootorder size 0x0 > fw_cfg_modify_file: filename bios-geometry len 0x0 > fw_cfg_add_file_callback: filename bios-geometry size 0x0 >=20 >=20 > Initiate migration Source --> Target, >=20 > ram_load_precopy: Ram blk mach-virt.ram length 0x100000000 used_length 0x= 100000000 > ram_load_precopy: Ram blk mem1 length 0x40000000 used_length 0x40000000 > ram_load_precopy: Ram blk mem2 length 0x40000000 used_length 0x40000000 > ram_load_precopy: Ram blk virt.flash0 length 0x4000000 used_length 0x4000= 000 > ram_load_precopy: Ram blk virt.flash1 length 0x4000000 used_length 0x4000= 000 > ram_load_precopy: Ram blk /rom@etc/acpi/tables length 0x6000 used_length = 0x6000 > ram_load_precopy: Ram blk 0000:00:01.0/virtio-net-pci.rom length 0x40000 = used_length 0x40000 > ram_load_precopy: Ram blk /rom@etc/table-loader length 0x1000 used_length= 0x1000 > ram_load_precopy: Ram blk /rom@etc/acpi/rsdp length 0x1000 used_length 0x= 1000 >=20 >=20 > root@ubuntu:/# cat /dev/pmem > pmem0 pmem1 =20 >=20 > From the logs, it looks like the ram_load_precopy() --> qemu_ram_resize()= is not > called as length =3D=3D used_length and both seems to be page aligned val= ues. > And from https://github.com/qemu/qemu/blob/master/migration/ram.c#L3421 > qemu_ram_resize() is called with length if length !=3D used_length. Assume on your source, the old size is 12345 bytes. So 16384 aligned up (4 pages). Assume on your target, the new size is 123456 bytes, so 126976 aligned up (31 pages). If you migrate from source to destination, the migration code would resize to 16384, although the "actual size" is 12345. The callback will be called with the aligned size, not the actual size. Same the other way around. That's what's inconsistent IMHO. --=20 Thanks, David / dhildenb