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(p200300cbc7140d00a1abbff4268fd7c5.dip0.t-ipconnect.de. [2003:cb:c714:d00:a1ab:bff4:268f:d7c5]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-37d081f74b0sm2969369f8f.16.2024.10.04.03.14.35 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 04 Oct 2024 03:14:36 -0700 (PDT) Message-ID: <2143f803-439e-4b8b-ae92-07caa913d646@redhat.com> Date: Fri, 4 Oct 2024 12:14:35 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH V2 01/13] machine: alloc-anon option To: Peter Xu , Steve Sistare Cc: qemu-devel@nongnu.org, Fabiano Rosas , Marcel Apfelbaum , Eduardo Habkost , Philippe Mathieu-Daude , Paolo Bonzini , "Daniel P. Berrange" , Markus Armbruster , Igor Mammedov References: <1727725244-105198-1-git-send-email-steven.sistare@oracle.com> <1727725244-105198-2-git-send-email-steven.sistare@oracle.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: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=170.10.129.124; envelope-from=david@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.143, 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, 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 03.10.24 18:14, Peter Xu wrote: > On Mon, Sep 30, 2024 at 12:40:32PM -0700, Steve Sistare wrote: >> Allocate anonymous memory using mmap MAP_ANON or memfd_create depending >> on the value of the anon-alloc machine property. This option applies to >> memory allocated as a side effect of creating various devices. It does >> not apply to memory-backend-objects, whether explicitly specified on >> the command line, or implicitly created by the -m command line option. >> >> The memfd option is intended to support new migration modes, in which the >> memory region can be transferred in place to a new QEMU process, by sending >> the memfd file descriptor to the process. Memory contents are preserved, >> and if the mode also transfers device descriptors, then pages that are >> locked in memory for DMA remain locked. This behavior is a pre-requisite >> for supporting vfio, vdpa, and iommufd devices with the new modes. >> >> Signed-off-by: Steve Sistare > > [Igor seems missing in the loop; added] > >> --- >> hw/core/machine.c | 19 +++++++++++++++++++ >> include/hw/boards.h | 1 + >> qapi/machine.json | 14 ++++++++++++++ >> qemu-options.hx | 11 +++++++++++ >> system/physmem.c | 35 +++++++++++++++++++++++++++++++++++ >> system/trace-events | 3 +++ >> 6 files changed, 83 insertions(+) >> >> diff --git a/hw/core/machine.c b/hw/core/machine.c >> index adaba17..a89a32b 100644 >> --- a/hw/core/machine.c >> +++ b/hw/core/machine.c >> @@ -460,6 +460,20 @@ static void machine_set_mem_merge(Object *obj, bool value, Error **errp) >> ms->mem_merge = value; >> } >> >> +static int machine_get_anon_alloc(Object *obj, Error **errp) >> +{ >> + MachineState *ms = MACHINE(obj); >> + >> + return ms->anon_alloc; >> +} >> + >> +static void machine_set_anon_alloc(Object *obj, int value, Error **errp) >> +{ >> + MachineState *ms = MACHINE(obj); >> + >> + ms->anon_alloc = value; >> +} >> + >> static bool machine_get_usb(Object *obj, Error **errp) >> { >> MachineState *ms = MACHINE(obj); >> @@ -1078,6 +1092,11 @@ static void machine_class_init(ObjectClass *oc, void *data) >> object_class_property_set_description(oc, "mem-merge", >> "Enable/disable memory merge support"); >> >> + object_class_property_add_enum(oc, "anon-alloc", "AnonAllocOption", >> + &AnonAllocOption_lookup, >> + machine_get_anon_alloc, >> + machine_set_anon_alloc); >> + >> object_class_property_add_bool(oc, "usb", >> machine_get_usb, machine_set_usb); >> object_class_property_set_description(oc, "usb", >> diff --git a/include/hw/boards.h b/include/hw/boards.h >> index 5966069..5a87647 100644 >> --- a/include/hw/boards.h >> +++ b/include/hw/boards.h >> @@ -393,6 +393,7 @@ struct MachineState { >> bool enable_graphics; >> ConfidentialGuestSupport *cgs; >> HostMemoryBackend *memdev; >> + AnonAllocOption anon_alloc; >> /* >> * convenience alias to ram_memdev_id backend memory region >> * or to numa container memory region >> diff --git a/qapi/machine.json b/qapi/machine.json >> index a6b8795..d4a63f5 100644 >> --- a/qapi/machine.json >> +++ b/qapi/machine.json >> @@ -1898,3 +1898,17 @@ >> { 'command': 'x-query-interrupt-controllers', >> 'returns': 'HumanReadableText', >> 'features': [ 'unstable' ]} >> + >> +## >> +# @AnonAllocOption: >> +# >> +# An enumeration of the options for allocating anonymous guest memory. >> +# >> +# @mmap: allocate using mmap MAP_ANON >> +# >> +# @memfd: allocate using memfd_create >> +# >> +# Since: 9.2 >> +## >> +{ 'enum': 'AnonAllocOption', >> + 'data': [ 'mmap', 'memfd' ] } >> diff --git a/qemu-options.hx b/qemu-options.hx >> index d94e2cb..90ab943 100644 >> --- a/qemu-options.hx >> +++ b/qemu-options.hx >> @@ -38,6 +38,7 @@ DEF("machine", HAS_ARG, QEMU_OPTION_machine, \ >> " nvdimm=on|off controls NVDIMM support (default=off)\n" >> " memory-encryption=@var{} memory encryption object to use (default=none)\n" >> " hmat=on|off controls ACPI HMAT support (default=off)\n" >> + " anon-alloc=mmap|memfd allocate anonymous guest RAM using mmap MAP_ANON or memfd_create (default: mmap)\n" >> " memory-backend='backend-id' specifies explicitly provided backend for main RAM (default=none)\n" >> " cxl-fmw.0.targets.0=firsttarget,cxl-fmw.0.targets.1=secondtarget,cxl-fmw.0.size=size[,cxl-fmw.0.interleave-granularity=granularity]\n", >> QEMU_ARCH_ALL) >> @@ -101,6 +102,16 @@ SRST >> Enables or disables ACPI Heterogeneous Memory Attribute Table >> (HMAT) support. The default is off. >> >> + ``anon-alloc=mmap|memfd`` >> + Allocate anonymous guest RAM using mmap MAP_ANON (the default) >> + or memfd_create. This option applies to memory allocated as a >> + side effect of creating various devices. It does not apply to >> + memory-backend-objects, whether explicitly specified on the >> + command line, or implicitly created by the -m command line >> + option. >> + >> + Some migration modes require anon-alloc=memfd. >> + >> ``memory-backend='id'`` >> An alternative to legacy ``-mem-path`` and ``mem-prealloc`` options. >> Allows to use a memory backend as main RAM. >> diff --git a/system/physmem.c b/system/physmem.c >> index dc1db3a..174f7e0 100644 >> --- a/system/physmem.c >> +++ b/system/physmem.c >> @@ -47,6 +47,7 @@ >> #include "qemu/qemu-print.h" >> #include "qemu/log.h" >> #include "qemu/memalign.h" >> +#include "qemu/memfd.h" >> #include "exec/memory.h" >> #include "exec/ioport.h" >> #include "sysemu/dma.h" >> @@ -69,6 +70,8 @@ >> >> #include "qemu/pmem.h" >> >> +#include "qapi/qapi-types-migration.h" >> +#include "migration/options.h" >> #include "migration/vmstate.h" >> >> #include "qemu/range.h" >> @@ -1849,6 +1852,35 @@ static void ram_block_add(RAMBlock *new_block, Error **errp) >> qemu_mutex_unlock_ramlist(); >> return; >> } >> + >> + } else if (current_machine->anon_alloc == ANON_ALLOC_OPTION_MEMFD && >> + !object_dynamic_cast(new_block->mr->parent_obj.parent, >> + TYPE_MEMORY_BACKEND)) { > > This is pretty fragile.. if someone adds yet another layer on top of memory > backend objects, the ownership links can change and this might silently run > into something else even without any warning.. > > I wished we dig into what is missing, but maybe that's too trivial. If > not, we still need to make this as solid. Perhaps that can be a ram flag > and let relevant callers pass in that flag explicitly. How would they decide whether or not we want to set the flag in the current configuration? > > I think RAM_SHARED can actually be that flag already - I mean, in all paths > that we may create anon mem (but not memory-backend-* objects), is it > always safe we always switch to RAM_SHARED from anon? Do you mean only setting the flag (-> anonymous shmem) or switching also to memfd, which is a bigger change? -- Cheers, David / dhildenb