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[2003:cb:c71b:2c00:7bfb:29fe:9e6f:2e65]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3862f0e6ea2sm10526542f8f.79.2024.12.09.13.11.29 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 09 Dec 2024 13:11:31 -0800 (PST) Message-ID: Date: Mon, 9 Dec 2024 22:11:29 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] hostmem-file: add the 'hmem' option To: "Luo, Zhigang" , "qemu-devel@nongnu.org" Cc: "kraxel@redhat.com" , Igor Mammedov References: <20241204171114.20033-1-Zhigang.Luo@amd.com> <5d4019cd-a3fb-4bed-8bab-e0388ccffee7@redhat.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: -25 X-Spam_score: -2.6 X-Spam_bar: -- X-Spam_report: (-2.6 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.489, 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_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_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 06.12.24 18:58, Luo, Zhigang wrote: > [AMD Official Use Only - AMD Internal Distribution Only] > > Hi David, Hi! > > Thanks for your comments. > Let me give you some background for this patch. > I am currently engaged in a project that requires to pass the EFI_MEMORY_SP (Special Purpose Memory) type memory from host to a virtual machine within QEMU. This memory needs to be EFI_MEMORY_SP type in the virtual machine as well. > This particular memory type is essential for the functionality of my project. Which exact guest memory will be backed by this memory? All guest-memory? And, what is the guest OS going to do with this memory? Usually, this SP memory (dax, cxl, ...) is not used as boot memory. Like on a bare metal system, one would expect that only CXL memory will be marked as special and put aside to the cxl driver, such that the OS can boot on ordinary DIMMs, such that cxl can online it etc. So maybe you would want to expose this memory using CXL-mem device to the VM? Or a DIMM? I assume the alternative is to tell the VM on the Linux kernel cmdline to set EFI_MEMORY_SP on this memory. I recall that there is a way to achieve that. > In Linux, the SPM memory will be claimed by hmem-dax driver by default. With this patch I can use the following config to pass the SPM memory to guest VM. > -object memory-backend-file,size=30G,id=m1,mem-path=/dev/dax0.0,prealloc=on,align=1G,hmem=on > > I was thinking to change the option name from "hmem" to "spm" to avoid confusion. Likely it should be specified elsewhere, that you want specific guest RAM ranges to be EFI_MEMORY_SP. For a DIMM, it could be a property, similarly maybe for CXL-mem devices (no expert on that). For boot memory / machine memory it could be a machine property. But I'll first have to learn which ranges you actually want to expose that way, and what the VM will do with that information. > > Do you have any suggestions to achieve this more reasonable? The problem with qemu_ram_foreach_block() is that you would indicate also DIMMs, virtio-mem, ... and even RAMBlocks that are not even used for backing anything to the VM as EFI_MEMORY_SP, which is wrong. > > Thanks, > Zhigang > > -----Original Message----- > From: David Hildenbrand > Sent: Friday, December 6, 2024 5:08 AM > To: Luo, Zhigang ; qemu-devel@nongnu.org > Cc: kraxel@redhat.com; Igor Mammedov > Subject: Re: [PATCH] hostmem-file: add the 'hmem' option > > On 04.12.24 18:11, Zhigang Luo wrote: >> This boolean option 'hmem' allows users to set a memory region from >> memory-backend-file as heterogeneous memory. If 'hmem=on', QEMU will >> set the flag RAM_HMEM in the RAM block of the corresponding memory >> region and set the e820 type to E820_SOFT_RESERVED for this region. >> > > Hi, > > ./scripts/get_maintainer.pl is your friend to figure out whom to CC on patches. > > In general: not a fan. You seem to be abusing memory backend properties > + RAM flags to merely modify how memory is going to be exposed in the > memory map on x86. > > It's not even clear why heterogeneous memory should be exposed like > that, and how reasonable it is to essentially expose all of guest RAM as > E820_SOFT_RESERVED. > > > Note that the whole "pmem=on" case was very different, because it > required mmap() modifications. > >> Signed-off-by: Zhigang Luo >> --- >> backends/hostmem-file.c | 23 +++++++++++++++++++++++ >> hw/i386/e820_memory_layout.h | 1 + >> hw/i386/pc.c | 16 ++++++++++++++++ >> include/exec/cpu-common.h | 1 + >> include/exec/memory.h | 3 +++ >> qapi/qom.json | 4 ++++ >> system/physmem.c | 7 ++++++- >> 7 files changed, 54 insertions(+), 1 deletion(-) >> >> diff --git a/backends/hostmem-file.c b/backends/hostmem-file.c >> index 7e5072e33e..5ddfdbaf86 100644 >> --- a/backends/hostmem-file.c >> +++ b/backends/hostmem-file.c >> @@ -32,6 +32,7 @@ struct HostMemoryBackendFile { >> uint64_t offset; >> bool discard_data; >> bool is_pmem; >> + bool is_hmem; >> bool readonly; >> OnOffAuto rom; >> }; >> @@ -88,6 +89,7 @@ file_backend_memory_alloc(HostMemoryBackend *backend, Error **errp) >> ram_flags |= backend->reserve ? 0 : RAM_NORESERVE; >> ram_flags |= backend->guest_memfd ? RAM_GUEST_MEMFD : 0; >> ram_flags |= fb->is_pmem ? RAM_PMEM : 0; >> + ram_flags |= fb->is_hmem ? RAM_HMEM : 0; >> ram_flags |= RAM_NAMED_FILE; >> return memory_region_init_ram_from_file(&backend->mr, OBJECT(backend), name, >> backend->size, fb->align, ram_flags, >> @@ -256,6 +258,25 @@ static void file_memory_backend_set_rom(Object *obj, Visitor *v, >> visit_type_OnOffAuto(v, name, &fb->rom, errp); >> } >> >> +static bool file_memory_backend_get_hmem(Object *o, Error **errp) >> +{ >> + return MEMORY_BACKEND_FILE(o)->is_hmem; >> +} >> + >> +static void file_memory_backend_set_hmem(Object *o, bool value, Error **errp) >> +{ >> + HostMemoryBackend *backend = MEMORY_BACKEND(o); >> + HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(o); >> + >> + if (host_memory_backend_mr_inited(backend)) { >> + error_setg(errp, "cannot change property 'hmem' of %s.", >> + object_get_typename(o)); >> + return; >> + } >> + >> + fb->is_hmem = value; >> +} >> + >> static void file_backend_unparent(Object *obj) >> { >> HostMemoryBackend *backend = MEMORY_BACKEND(obj); >> @@ -295,6 +316,8 @@ file_backend_class_init(ObjectClass *oc, void *data) >> object_class_property_add_bool(oc, "pmem", >> file_memory_backend_get_pmem, file_memory_backend_set_pmem); >> #endif >> + object_class_property_add_bool(oc, "hmem", >> + file_memory_backend_get_hmem, file_memory_backend_set_hmem); >> object_class_property_add_bool(oc, "readonly", >> file_memory_backend_get_readonly, >> file_memory_backend_set_readonly); >> diff --git a/hw/i386/e820_memory_layout.h b/hw/i386/e820_memory_layout.h >> index b50acfa201..8af6a9cfac 100644 >> --- a/hw/i386/e820_memory_layout.h >> +++ b/hw/i386/e820_memory_layout.h >> @@ -15,6 +15,7 @@ >> #define E820_ACPI 3 >> #define E820_NVS 4 >> #define E820_UNUSABLE 5 >> +#define E820_SOFT_RESERVED 0xEFFFFFFF >> >> struct e820_entry { >> uint64_t address; >> diff --git a/hw/i386/pc.c b/hw/i386/pc.c >> index 317aaca25a..41e9cc276c 100644 >> --- a/hw/i386/pc.c >> +++ b/hw/i386/pc.c >> @@ -785,6 +785,21 @@ static hwaddr pc_max_used_gpa(PCMachineState *pcms, uint64_t pci_hole64_size) >> return pc_above_4g_end(pcms) - 1; >> } >> >> +static int pc_update_hmem_memory(RAMBlock *rb, void *opaque) >> +{ >> + X86MachineState *x86ms = opaque; >> + ram_addr_t offset; >> + ram_addr_t length; >> + >> + if (qemu_ram_is_hmem(rb)) { >> + offset = qemu_ram_get_offset(rb) + (0x100000000ULL - x86ms->below_4g_mem_size); >> + length = qemu_ram_get_used_length(rb); >> + e820_add_entry(offset, length, E820_SOFT_RESERVED); >> + } > > I am pretty sure this will break in NUMA setups, where we have multiple > memory backends mapped in different locations. > > The whole "(0x100000000ULL - x86ms->below_4g_mem_size)" looks hacky. > > -- > Cheers, > > David / dhildenb > -- Cheers, David / dhildenb