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Szmigiero" To: qemu-devel@nongnu.org Cc: David Hildenbrand Subject: [PULL 1/9] memory-device: Support empty memory devices Date: Sun, 5 Nov 2023 12:47:49 +0100 Message-ID: <6c1b28e9e405da8cfb7296b9efa2b85650086784.1699184105.git.maciej.szmigiero@oracle.com> X-Mailer: git-send-email 2.42.0 In-Reply-To: References: 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=37.28.154.113; envelope-from=mail@maciej.szmigiero.name; helo=vps-vb.mhejs.net 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, 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-ZM-MESSAGEID: 1699184965930100001 Content-Type: text/plain; charset="utf-8" From: David Hildenbrand Let's support empty memory devices -- memory devices that don't have a memory device region in the current configuration. hv-balloon with an optional memdev is the primary use case. Signed-off-by: David Hildenbrand Signed-off-by: Maciej S. Szmigiero --- hw/mem/memory-device.c | 43 +++++++++++++++++++++++++++++++--- include/hw/mem/memory-device.h | 7 +++++- 2 files changed, 46 insertions(+), 4 deletions(-) diff --git a/hw/mem/memory-device.c b/hw/mem/memory-device.c index ae38f48f1676..db702ccad554 100644 --- a/hw/mem/memory-device.c +++ b/hw/mem/memory-device.c @@ -20,6 +20,22 @@ #include "exec/address-spaces.h" #include "trace.h" =20 +static bool memory_device_is_empty(const MemoryDeviceState *md) +{ + const MemoryDeviceClass *mdc =3D MEMORY_DEVICE_GET_CLASS(md); + Error *local_err =3D NULL; + MemoryRegion *mr; + + /* dropping const here is fine as we don't touch the memory region */ + mr =3D mdc->get_memory_region((MemoryDeviceState *)md, &local_err); + if (local_err) { + /* Not empty, we'll report errors later when ontaining the MR agai= n. */ + error_free(local_err); + return false; + } + return !mr; +} + static gint memory_device_addr_sort(gconstpointer a, gconstpointer b) { const MemoryDeviceState *md_a =3D MEMORY_DEVICE(a); @@ -249,6 +265,10 @@ static uint64_t memory_device_get_free_addr(MachineSta= te *ms, uint64_t next_addr; Range tmp; =20 + if (memory_device_is_empty(md)) { + continue; + } + range_init_nofail(&tmp, mdc->get_addr(md), memory_device_get_region_size(md, &error_abort)); =20 @@ -292,6 +312,7 @@ MemoryDeviceInfoList *qmp_memory_device_list(void) const MemoryDeviceClass *mdc =3D MEMORY_DEVICE_GET_CLASS(item->dat= a); MemoryDeviceInfo *info =3D g_new0(MemoryDeviceInfo, 1); =20 + /* Let's query infotmation even for empty memory devices. */ mdc->fill_device_info(md, info); =20 QAPI_LIST_APPEND(tail, info); @@ -311,7 +332,7 @@ static int memory_device_plugged_size(Object *obj, void= *opaque) const MemoryDeviceState *md =3D MEMORY_DEVICE(obj); const MemoryDeviceClass *mdc =3D MEMORY_DEVICE_GET_CLASS(obj); =20 - if (dev->realized) { + if (dev->realized && !memory_device_is_empty(md)) { *size +=3D mdc->get_plugged_size(md, &error_abort); } } @@ -337,6 +358,11 @@ void memory_device_pre_plug(MemoryDeviceState *md, Mac= hineState *ms, uint64_t addr, align =3D 0; MemoryRegion *mr; =20 + /* We support empty memory devices even without device memory. */ + if (memory_device_is_empty(md)) { + return; + } + if (!ms->device_memory) { error_setg(errp, "the configuration is not prepared for memory dev= ices" " (e.g., for memory hotplug), consider specifying= the" @@ -380,10 +406,17 @@ out: void memory_device_plug(MemoryDeviceState *md, MachineState *ms) { const MemoryDeviceClass *mdc =3D MEMORY_DEVICE_GET_CLASS(md); - const unsigned int memslots =3D memory_device_get_memslots(md); - const uint64_t addr =3D mdc->get_addr(md); + unsigned int memslots; + uint64_t addr; MemoryRegion *mr; =20 + if (memory_device_is_empty(md)) { + return; + } + + memslots =3D memory_device_get_memslots(md); + addr =3D mdc->get_addr(md); + /* * We expect that a previous call to memory_device_pre_plug() succeede= d, so * it can't fail at this point. @@ -408,6 +441,10 @@ void memory_device_unplug(MemoryDeviceState *md, Machi= neState *ms) const unsigned int memslots =3D memory_device_get_memslots(md); MemoryRegion *mr; =20 + if (memory_device_is_empty(md)) { + return; + } + /* * We expect that a previous call to memory_device_pre_plug() succeede= d, so * it can't fail at this point. diff --git a/include/hw/mem/memory-device.h b/include/hw/mem/memory-device.h index 3354d6c1667e..a1d62cc551ab 100644 --- a/include/hw/mem/memory-device.h +++ b/include/hw/mem/memory-device.h @@ -38,6 +38,10 @@ typedef struct MemoryDeviceState MemoryDeviceState; * address in guest physical memory can either be specified explicitly * or get assigned automatically. * + * Some memory device might not own a memory region in certain device + * configurations. Such devices can logically get (un)plugged, however, + * empty memory devices are mostly ignored by the memory device code. + * * Conceptually, memory devices only span one memory region. If multiple * successive memory regions are used, a covering memory region has to * be provided. Scattered memory regions are not supported for single @@ -91,7 +95,8 @@ struct MemoryDeviceClass { uint64_t (*get_plugged_size)(const MemoryDeviceState *md, Error **errp= ); =20 /* - * Return the memory region of the memory device. + * Return the memory region of the memory device. If the device is + * completely empty, returns NULL without an error. * * Called when (un)plugging the memory device, to (un)map the * memory region in guest physical memory, but also to detect the