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Thu, 6 Feb 2020 13:17:13 +0000 (UTC) Received: from [10.36.118.128] (unknown [10.36.118.128]) by smtp.corp.redhat.com (Postfix) with ESMTP id B9DF326FC5; Thu, 6 Feb 2020 13:16:59 +0000 (UTC) Subject: Re: [PATCH v1 08/13] util/mmap-alloc: Prepare for resizable mmaps To: =?UTF-8?Q?Murilo_Opsfelder_Ara=c3=bajo?= References: <20200203183125.164879-1-david@redhat.com> <2036195.sfUKtyktLc@kermit.br.ibm.com> <5c261bcd-44df-b4a0-451d-83ec6ac48059@redhat.com> <6458667.Kg4MDSSyM0@kermit.br.ibm.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: <196ab5be-c851-cc20-01ea-a2507333b3f4@redhat.com> Date: Thu, 6 Feb 2020 14:16:58 +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: <6458667.Kg4MDSSyM0@kermit.br.ibm.com> Content-Language: en-US X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-MC-Unique: hdl39RseO-Ge1yunAgteag-1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=WINDOWS-1252 Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 205.139.110.120 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: Eduardo Habkost , "Michael S . Tsirkin" , qemu-devel@nongnu.org, "Dr . David Alan Gilbert" , Greg Kurz , Paolo Bonzini , Richard Henderson Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 06.02.20 13:31, Murilo Opsfelder Ara=FAjo wrote: > Hello, David. >=20 > On Thursday, February 6, 2020 5:52:26 AM -03 David Hildenbrand wrote: >> On 06.02.20 00:00, Murilo Opsfelder Ara=FAjo wrote: >>> Hello, David. >>> >>> On Monday, February 3, 2020 3:31:20 PM -03 David Hildenbrand wrote: >>>> When shrinking a mmap we want to re-reserve the already populated area= . >>>> When growing a memory region, we want to populate starting with a give= n >>>> fd_offset. Prepare by allowing to pass these parameters. >>>> >>>> Also, let's make sure we always process full pages, to avoid >>>> unmapping/remapping pages that are already in use when >>>> growing/shrinking. (existing callers seem to guarantee this, but that'= s >>>> not obvious) >>>> >>>> Cc: "Michael S. Tsirkin" >>>> Cc: Greg Kurz >>>> Cc: Murilo Opsfelder Araujo >>>> Cc: Eduardo Habkost >>>> Cc: "Dr. David Alan Gilbert" >>>> Signed-off-by: David Hildenbrand >>>> --- >>>> >>>> util/mmap-alloc.c | 32 +++++++++++++++++++++----------- >>>> 1 file changed, 21 insertions(+), 11 deletions(-) >>>> >>>> diff --git a/util/mmap-alloc.c b/util/mmap-alloc.c >>>> index f043ccb0ab..63ad6893b7 100644 >>>> --- a/util/mmap-alloc.c >>>> +++ b/util/mmap-alloc.c >>>> @@ -83,12 +83,12 @@ size_t qemu_mempath_getpagesize(const char *mem_pa= th) >>>> >>>> } >>>> >>>> /* >>>> >>>> - * Reserve a new memory region of the requested size to be used for >>>> mapping - * from the given fd (if any). >>>> + * Reserve a new memory region of the requested size or re-reserve pa= rts >>>> + * of an existing region to be used for mapping from the given fd (if >>>> any). */ >>>> -static void *mmap_reserve(size_t size, int fd) >>>> +static void *mmap_reserve(void *ptr, size_t size, int fd) >>>> >>>> { >>>> >>>> - int flags =3D MAP_PRIVATE; >>>> + int flags =3D MAP_PRIVATE | (ptr ? MAP_FIXED : 0); >>>> >>>> #if defined(__powerpc64__) && defined(__linux__) >>>> >>>> /* >>>> >>>> @@ -111,19 +111,23 @@ static void *mmap_reserve(size_t size, int fd) >>>> >>>> flags |=3D MAP_ANONYMOUS; >>>> >>>> #endif >>>> >>>> - return mmap(0, size, PROT_NONE, flags, fd, 0); >>>> + return mmap(ptr, size, PROT_NONE, flags, fd, 0); >>>> >>>> } >>>> >>>> /* >>>> >>>> * Populate memory in a reserved region from the given fd (if any). >>>> */ >>>> >>>> -static void *mmap_populate(void *ptr, size_t size, int fd, bool share= d, >>>> - bool is_pmem) >>>> +static void *mmap_populate(void *ptr, size_t size, int fd, size_t >>>> fd_offset, + bool shared, bool is_pmem) >>>> >>>> { >>>> >>>> int map_sync_flags =3D 0; >>>> int flags =3D MAP_FIXED; >>>> void *new_ptr; >>>> >>>> + if (fd =3D=3D -1) { >>>> + fd_offset =3D 0; >>>> + } >>>> + >>>> >>>> flags |=3D fd =3D=3D -1 ? MAP_ANONYMOUS : 0; >>>> flags |=3D shared ? MAP_SHARED : MAP_PRIVATE; >>>> if (shared && is_pmem) { >>>> >>>> @@ -131,7 +135,7 @@ static void *mmap_populate(void *ptr, size_t size, >>>> int >>>> fd, bool shared, } >>>> >>>> new_ptr =3D mmap(ptr, size, PROT_READ | PROT_WRITE, flags | >>>> >>>> map_sync_flags, - fd, 0); >>>> + fd, fd_offset); >>>> >>>> if (new_ptr =3D=3D MAP_FAILED && map_sync_flags) { >>>> >>>> if (errno =3D=3D ENOTSUP) { >>>> >>>> char *proc_link =3D g_strdup_printf("/proc/self/fd/%d", f= d); >>>> >>>> @@ -153,7 +157,7 @@ static void *mmap_populate(void *ptr, size_t size, >>>> int >>>> fd, bool shared, * If mmap failed with MAP_SHARED_VALIDATE | MAP_SYNC,= we >>>> will try * again without these flags to handle backwards compatibility= . >>>> */ >>>> - new_ptr =3D mmap(ptr, size, PROT_READ | PROT_WRITE, flags, fd= , 0); >>>> + new_ptr =3D mmap(ptr, size, PROT_READ | PROT_WRITE, flags, fd= , >>>> fd_offset); } >>>> >>>> return new_ptr; >>>> >>>> } >>>> >>>> @@ -178,13 +182,16 @@ void *qemu_ram_mmap(int fd, >>>> >>>> size_t offset, total; >>>> void *ptr, *guardptr; >>>> >>>> + /* we can only map whole pages */ >>>> + size =3D QEMU_ALIGN_UP(size, pagesize); >>>> + >>> >>> Caller already rounds up size to block->page_size. >>> >>> Why this QEMU_ALIGN_UP is necessary? >> >> Thanks for having a look >> >> I guess you read the patch description, right? :) >> >> "(existing callers seem to guarantee this, but that's >> not obvious)" >> >> Do you prefer a g_assert(IS_ALIGNED()) instead? >=20 > I guess you mean QEMU_IS_ALIGNED(). But yes, I think we could just check > alignments here, so callers do the alignments first. Yeh, you got the idea :) I'll convert these to asserts for now. Thanks! --=20 Thanks, David / dhildenb