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Tue, 04 Jul 2023 01:06:46 -0700 (PDT) From: Mattias Nissler To: qemu-devel@nongnu.org Cc: Elena Ufimtseva , Jagannathan Raman , =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= , Paolo Bonzini , Peter Xu , stefanha@redhat.com, David Hildenbrand , john.levon@nutanix.com, Mattias Nissler Subject: [PATCH 1/3] softmmu: Support concurrent bounce buffers Date: Tue, 4 Jul 2023 01:06:25 -0700 Message-Id: <20230704080628.852525-2-mnissler@rivosinc.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230704080628.852525-1-mnissler@rivosinc.com> References: <20230704080628.852525-1-mnissler@rivosinc.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=2607:f8b0:4864:20::435; envelope-from=mnissler@rivosinc.com; helo=mail-pf1-x435.google.com X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 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+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @rivosinc-com.20221208.gappssmtp.com) X-ZM-MESSAGEID: 1688458080835100003 Content-Type: text/plain; charset="utf-8" It is not uncommon for device models to request mapping of several DMA regions at the same time. An example is igb (and probably other net devices as well) when a packet is spread across multiple descriptors. In order to support this when indirect DMA is used, as is the case when running the device model in a vfio-server process without mmap()-ed DMA, this change allocates DMA bounce buffers dynamically instead of supporting only a single buffer. Signed-off-by: Mattias Nissler --- softmmu/physmem.c | 74 ++++++++++++++++++++++------------------------- 1 file changed, 35 insertions(+), 39 deletions(-) diff --git a/softmmu/physmem.c b/softmmu/physmem.c index bda475a719..56130b5a1d 100644 --- a/softmmu/physmem.c +++ b/softmmu/physmem.c @@ -2904,13 +2904,11 @@ void cpu_flush_icache_range(hwaddr start, hwaddr le= n) =20 typedef struct { MemoryRegion *mr; - void *buffer; hwaddr addr; - hwaddr len; - bool in_use; + uint8_t buffer[]; } BounceBuffer; =20 -static BounceBuffer bounce; +static size_t bounce_buffers_in_use; =20 typedef struct MapClient { QEMUBH *bh; @@ -2947,7 +2945,7 @@ void cpu_register_map_client(QEMUBH *bh) QLIST_INSERT_HEAD(&map_client_list, client, link); /* Write map_client_list before reading in_use. */ smp_mb(); - if (!qatomic_read(&bounce.in_use)) { + if (qatomic_read(&bounce_buffers_in_use)) { cpu_notify_map_clients_locked(); } qemu_mutex_unlock(&map_client_list_lock); @@ -3076,31 +3074,24 @@ void *address_space_map(AddressSpace *as, RCU_READ_LOCK_GUARD(); fv =3D address_space_to_flatview(as); mr =3D flatview_translate(fv, addr, &xlat, &l, is_write, attrs); + memory_region_ref(mr); =20 if (!memory_access_is_direct(mr, is_write)) { - if (qatomic_xchg(&bounce.in_use, true)) { - *plen =3D 0; - return NULL; - } - /* Avoid unbounded allocations */ - l =3D MIN(l, TARGET_PAGE_SIZE); - bounce.buffer =3D qemu_memalign(TARGET_PAGE_SIZE, l); - bounce.addr =3D addr; - bounce.len =3D l; - - memory_region_ref(mr); - bounce.mr =3D mr; + qatomic_inc_fetch(&bounce_buffers_in_use); + + BounceBuffer *bounce =3D g_malloc(l + sizeof(BounceBuffer)); + bounce->addr =3D addr; + bounce->mr =3D mr; + if (!is_write) { flatview_read(fv, addr, MEMTXATTRS_UNSPECIFIED, - bounce.buffer, l); + bounce->buffer, l); } =20 *plen =3D l; - return bounce.buffer; + return bounce->buffer; } =20 - - memory_region_ref(mr); *plen =3D flatview_extend_translation(fv, addr, len, mr, xlat, l, is_write, attrs); fuzz_dma_read_cb(addr, *plen, mr); @@ -3114,31 +3105,36 @@ void *address_space_map(AddressSpace *as, void address_space_unmap(AddressSpace *as, void *buffer, hwaddr len, bool is_write, hwaddr access_len) { - if (buffer !=3D bounce.buffer) { - MemoryRegion *mr; - ram_addr_t addr1; + MemoryRegion *mr; + ram_addr_t addr1; + + mr =3D memory_region_from_host(buffer, &addr1); + if (mr =3D=3D NULL) { + /* + * Must be a bounce buffer (unless the caller passed a pointer whi= ch + * wasn't returned by address_space_map, which is illegal). + */ + BounceBuffer *bounce =3D container_of(buffer, BounceBuffer, buffer= ); =20 - mr =3D memory_region_from_host(buffer, &addr1); - assert(mr !=3D NULL); if (is_write) { - invalidate_and_set_dirty(mr, addr1, access_len); + address_space_write(as, bounce->addr, MEMTXATTRS_UNSPECIFIED, + bounce->buffer, access_len); } - if (xen_enabled()) { - xen_invalidate_map_cache_entry(buffer); + memory_region_unref(bounce->mr); + g_free(bounce); + + if (qatomic_dec_fetch(&bounce_buffers_in_use) =3D=3D 1) { + cpu_notify_map_clients(); } - memory_region_unref(mr); return; } + + if (xen_enabled()) { + xen_invalidate_map_cache_entry(buffer); + } if (is_write) { - address_space_write(as, bounce.addr, MEMTXATTRS_UNSPECIFIED, - bounce.buffer, access_len); - } - qemu_vfree(bounce.buffer); - bounce.buffer =3D NULL; - memory_region_unref(bounce.mr); - /* Clear in_use before reading map_client_list. */ - qatomic_set_mb(&bounce.in_use, false); - cpu_notify_map_clients(); + invalidate_and_set_dirty(mr, addr1, access_len); + } } =20 void *cpu_physical_memory_map(hwaddr addr, --=20 2.34.1