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[91.12.106.95]) by smtp.gmail.com with ESMTPSA id bi26sm8894215ejb.120.2021.03.09.12.27.11 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 09 Mar 2021 12:27:12 -0800 (PST) From: David Hildenbrand Mime-Version: 1.0 (1.0) Subject: Re: [PATCH v3 09/12] util/mmap-alloc: Pass flags instead of separate bools to qemu_ram_mmap() Date: Tue, 9 Mar 2021 21:27:10 +0100 Message-Id: <29372C8B-7F57-4AB6-99DB-5E73179D7555@redhat.com> References: <20210309200451.GF763132@xz-x1> In-Reply-To: <20210309200451.GF763132@xz-x1> To: Peter Xu X-Mailer: iPhone Mail (18D52) Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=david@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Received-SPF: pass client-ip=216.205.24.124; envelope-from=david@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -29 X-Spam_score: -3.0 X-Spam_bar: --- X-Spam_report: (-3.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.251, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, 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: Marcel Apfelbaum , Murilo Opsfelder Araujo , Cornelia Huck , Eduardo Habkost , "Michael S. Tsirkin" , Stefan Weil , David Hildenbrand , Richard Henderson , "Dr. David Alan Gilbert" , Juan Quintela , qemu-devel@nongnu.org, Halil Pasic , Christian Borntraeger , Greg Kurz , Stefan Hajnoczi , Igor Mammedov , Thomas Huth , Paolo Bonzini , =?utf-8?Q?Philippe_Mathieu-Daud=C3=A9?= , Igor Kotrasinski Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" > Am 09.03.2021 um 21:04 schrieb Peter Xu : >=20 > =EF=BB=BFOn Mon, Mar 08, 2021 at 04:05:57PM +0100, David Hildenbrand wrot= e: >> Let's introduce a new set of flags that abstract mmap logic and replace >> our current set of bools, to prepare for another flag. >>=20 >> Signed-off-by: David Hildenbrand >> --- >> include/qemu/mmap-alloc.h | 17 +++++++++++------ >> softmmu/physmem.c | 8 +++++--- >> util/mmap-alloc.c | 14 +++++++------- >> util/oslib-posix.c | 3 ++- >> 4 files changed, 25 insertions(+), 17 deletions(-) >>=20 >> diff --git a/include/qemu/mmap-alloc.h b/include/qemu/mmap-alloc.h >> index 456ff87df1..55664ea9f3 100644 >> --- a/include/qemu/mmap-alloc.h >> +++ b/include/qemu/mmap-alloc.h >> @@ -6,6 +6,15 @@ size_t qemu_fd_getpagesize(int fd); >>=20 >> size_t qemu_mempath_getpagesize(const char *mem_path); >>=20 >> +/* Map PROT_READ instead of PROT_READ|PROT_WRITE. */ >> +#define QEMU_RAM_MMAP_READONLY (1 << 0) >> + >> +/* Map MAP_SHARED instead of MAP_PRIVATE. */ >> +#define QEMU_RAM_MMAP_SHARED (1 << 1) >> + >> +/* Map MAP_SYNC|MAP_SHARED_VALIDATE if possible, fallback and warn othe= rwise. */ >> +#define QEMU_RAM_MMAP_PMEM (1 << 2) >=20 > Sorry to speak late - I just noticed that is_pmem can actually be convert= ed too > with "MAP_SYNC | MAP_SHARED_VALIDATE". We can even define MAP_PMEM_EXTRA= for > use within qemu if we want. Then we can avoid one layer of QEMU_RAM_* by > directly using MAP_*, I think? >=20 No problem :) I don=E2=80=98t think passing in random MAP_ flags is a good = interface (we would at least need an allow list). I like the abstraction / explicit semenatics of QEMU_RAM_MMAP_PMEM as spel= led out in the comment. Doing the fallback when passing in the mmap flags i= s a little ugly. We could do the fallback in the caller, I think I remember= there is only a single call site. PROT_READ won=E2=80=98t be covered as well, not sure if passing in protecti= ons improves the interface. Long story short, I like the abstraction provided by these flags, only expo= rting what we actually support/abstracting it, and setting some MAP_ flags = automatically (MAP_PRIVATE, MAP_ANON) instead of having to spell that put i= n the caller. > --=20 > Peter Xu >=20