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[83.57.175.68]) by smtp.gmail.com with ESMTPSA id n6sm7609864wmd.27.2021.03.01.03.59.26 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 01 Mar 2021 03:59:26 -0800 (PST) Subject: Re: [RFC PATCH 1/3] exec/memory: Introduce memory_region_init_rom_device_from_file() To: Stefano Garzarella References: <20210225230238.3719051-1-philmd@redhat.com> <20210225230238.3719051-2-philmd@redhat.com> <20210301115317.i7qctejcit6zcbac@steredhat> From: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= Message-ID: Date: Mon, 1 Mar 2021 12:59:25 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.0 MIME-Version: 1.0 In-Reply-To: <20210301115317.i7qctejcit6zcbac@steredhat> Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=philmd@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=216.205.24.124; envelope-from=philmd@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 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, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=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: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kevin Wolf , qemu-block@nongnu.org, Xu Yandong , qemu-devel@nongnu.org, Markus Armbruster , David Edmondson , Zheng Xiang , haibinzhang , Stefan Hajnoczi , Paolo Bonzini , Max Reitz Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 3/1/21 12:53 PM, Stefano Garzarella wrote: > I don't know this code very well, but I have a couple of comments below :-) > > On Fri, Feb 26, 2021 at 12:02:36AM +0100, Philippe Mathieu-Daudé wrote: >> Introduce memory_region_init_rom_device_from_file() which mmap >> the backing file of ROM devices. This allows to reduce QEMU memory >> footprint as the same file can be shared between multiple instances >> of QEMU. >> >> Signed-off-by: Philippe Mathieu-Daudé >> --- >> include/exec/memory.h | 85 +++++++++++++++++++++++++++++++++++++ >> softmmu/memory.c      | 98 +++++++++++++++++++++++++++++++++++++++++++ >> 2 files changed, 183 insertions(+) ... >> +void memory_region_init_rom_device_from_file_nomigrate(MemoryRegion *mr, >> +                                                       Object *owner, >> +                                                       const >> MemoryRegionOps *ops, >> +                                                       void *opaque, >> +                                                       const char *name, >> +                                                       uint64_t size, >> +                                                       uint64_t align, >> +                                                       uint32_t >> ram_flags, >> +                                                       const char *path, >> +                                                       bool readonly, >> +                                                       Error **errp) >> +{ >> +    Error *err = NULL; >> + >> +    assert(ops); >> +#ifdef CONFIG_POSIX >> +    memory_region_init(mr, owner, name, size); >> +    mr->opaque = opaque; >> +    mr->ops = ops; >> +    mr->rom_device = true; >> +    mr->readonly = readonly; >> +    mr->ram = true; >> +    mr->align = align; >> +    mr->terminates = true; >> +    mr->destructor = memory_region_destructor_ram; >> +    mr->ram_block = qemu_ram_alloc_from_file(size, mr, ram_flags, path, >> +                                             readonly, &err); >> +    if (err) { >> +        mr->size = int128_zero(); >> +        object_unparent(OBJECT(mr)); >> +        error_propagate(errp, err); >> +    } >> +#else >> +    g_autoptr(GError) gerr = NULL; >> +    gsize len; >> + >> +    memory_region_init(mr, owner, name, size); >> +    mr->ops = ops; >> +    mr->opaque = opaque; >> +    mr->terminates = true; >> +    mr->rom_device = true; > > Why when CONFIG_POSIX is defined we set 'mr->ram', 'mr->align', and > 'mr->readonly = readonly' but not here? > (I honestly don't know if they are important, I ask out of curiosity.  :-) I suppose we should and I forgot :/ > >> + >> +    if (!g_file_get_contents(path, &mr->contents, &len, &gerr)) { > > Should we do these steps in case of an error? > >           mr->size = int128_zero(); >           object_unparent(OBJECT(mr)); Yes... > >> +        error_setg(errp, "Unable to read '%s': %s", path, >> gerr->message); >> +        return; >> +    } >> +    mr->destructor = memory_region_destructor_contents; >> +    mr->contents = g_realloc(mr->contents, size); >> +    mr->ram_block = qemu_ram_alloc_from_ptr(size, mr->contents, mr, >> &err); >> +    if (err) { >> +        mr->size = int128_zero(); >> +        object_unparent(OBJECT(mr)); >> +        error_propagate(errp, err); >> +    } >> +#endif > > Maybe I would reorganize the code inside ifdef like this: > >         memory_region_init(mr, owner, name, size); >         mr->opaque = opaque; >         ... >     #ifdef CONFIG_POSIX >         mr->destructor = memory_region_destructor_ram; >         mr->ram_block = qemu_ram_alloc_from_file(...); >     #else >         if (!g_file_get_contents(..)) { >             ... >         } >         mr->destructor = memory_region_destructor_contents; >         mr->contents = g_realloc(mr->contents, size); >         mr->ram_block = qemu_ram_alloc_from_ptr(...) >     #endif > >         if (err) { >             ... >         } Yes, thanks :) > > I don't have a strong opinion, just an idea. > > Thanks, > Stefano