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Thu, 6 Feb 2020 15:13:17 +0000 (UTC) Received: from [10.36.118.128] (unknown [10.36.118.128]) by smtp.corp.redhat.com (Postfix) with ESMTP id 74EE610027A1; Thu, 6 Feb 2020 15:13:13 +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> <20200203183125.164879-9-david@redhat.com> <2036195.sfUKtyktLc@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: Date: Thu, 6 Feb 2020 16:13:12 +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: <2036195.sfUKtyktLc@kermit.br.ibm.com> Content-Language: en-US X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-MC-Unique: _e-uPQN9NyqD8MmYtjWSYA-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 00:00, Murilo Opsfelder Ara=FAjo wrote: > Hello, David. >=20 > 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 given >> 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_path= ) >> } >> >> /* >> - * Reserve a new memory region of the requested size to be used for map= ping >> - * from the given fd (if any). >> + * Reserve a new memory region of the requested size or re-reserve part= s >> + * of an existing region to be used for mapping from the given fd (if a= ny). >> */ >> -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 shared, >> - 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, i= nt >> 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", fd)= ; >> @@ -153,7 +157,7 @@ static void *mmap_populate(void *ptr, size_t size, i= nt >> fd, bool shared, * If mmap failed with MAP_SHARED_VALIDATE | MAP_SYNC, w= e >> 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); >> + >=20 > Caller already rounds up size to block->page_size. >=20 > Why this QEMU_ALIGN_UP is necessary? >=20 >> /* >> * Note: this always allocates at least one extra page of virtual >> address * space, even if size is already aligned. >> */ >> total =3D size + align; >=20 > If size was aligned above with pagesize boundary, why would this align be= =20 > necessary? >=20 > Can the pagesize differ from memory region align? Sorry, skipped this comment. Yes, e.g., we want to align ram blocks for KVM to hugepage size, to allow for transparent huge pages. So the comment still holds. --=20 Thanks, David / dhildenb