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envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=2607:f8b0:4864:20::102a; envelope-from=richy.liu.2002@gmail.com; helo=mail-pj1-x102a.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, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_ENVFROM_END_DIGIT=0.25, FREEMAIL_FROM=0.001, 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" X-ZohoMail-DKIM: pass (identity @gmail.com) X-ZM-MESSAGEID: 1658517932836100001 Content-Type: text/plain; charset="utf-8" Use a file-backed copy-on-write mmap region for snapshots. Restores are handled by remmaping the fixed region. Currently, the snapshot file save path (`filepath`) is hardcoded (to a path that is memory-backed on my machine). Signed-off-by: Richard Liu --- hw/misc/snapshot.c | 72 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 72 insertions(+) diff --git a/hw/misc/snapshot.c b/hw/misc/snapshot.c index 2690b331fd..510bf59dce 100644 --- a/hw/misc/snapshot.c +++ b/hw/misc/snapshot.c @@ -18,8 +18,63 @@ DECLARE_INSTANCE_CHECKER(SnapshotState, SNAPSHOT, struct SnapshotState { PCIDevice pdev; MemoryRegion mmio; + + // track saved stated to prevent re-saving + bool is_saved; + + // saved cpu and devices state + QIOChannelBuffer *ioc; }; =20 +// memory save location (for better performance, use tmpfs) +const char *filepath =3D "/Volumes/RAMDisk/snapshot_0"; + +static void save_snapshot(struct SnapshotState *s) { + if (s->is_saved) { + return; + } + s->is_saved =3D true; + + // save memory state to file + int fd =3D -1; + uint8_t *guest_mem =3D current_machine->ram->ram_block->host; + size_t guest_size =3D current_machine->ram->ram_block->max_length; + + fd =3D open(filepath, O_RDWR | O_CREAT | O_TRUNC, (mode_t)0600); + ftruncate(fd, guest_size); + + char *map =3D mmap(0, guest_size, PROT_READ | PROT_WRITE, MAP_SHARED, = fd, 0); + memcpy(map, guest_mem, guest_size); + msync(map, guest_size, MS_SYNC); + munmap(map, guest_size); + close(fd); + + // unmap the guest, we will now use a MAP_PRIVATE + munmap(guest_mem, guest_size); + + // map as MAP_PRIVATE to avoid carrying writes back to the saved file + fd =3D open(filepath, O_RDONLY); + mmap(guest_mem, guest_size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_= FIXED, fd, 0); +} + +static void restore_snapshot(struct SnapshotState *s) { + int fd =3D -1; + uint8_t *guest_mem =3D current_machine->ram->ram_block->host; + size_t guest_size =3D current_machine->ram->ram_block->max_length; + + if (!s->is_saved) { + fprintf(stderr, "[QEMU] ERROR: attempting to restore but state has= not been saved!\n"); + return; + } + + munmap(guest_mem, guest_size); + + // remap the snapshot at the same location + fd =3D open(filepath, O_RDONLY); + mmap(guest_mem, guest_size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_= FIXED, fd, 0); + close(fd); +} + static uint64_t snapshot_mmio_read(void *opaque, hwaddr addr, unsigned siz= e) { return 0; @@ -28,6 +83,21 @@ static uint64_t snapshot_mmio_read(void *opaque, hwaddr = addr, unsigned size) static void snapshot_mmio_write(void *opaque, hwaddr addr, uint64_t val, unsigned size) { + SnapshotState *snapshot =3D opaque; + (void)snapshot; + + switch (addr) { + case 0x00: + switch (val) { + case 0x101: + save_snapshot(snapshot); + break; + case 0x102: + restore_snapshot(snapshot); + break; + } + break; + } } =20 static const MemoryRegionOps snapshot_mmio_ops =3D { @@ -48,6 +118,8 @@ static const MemoryRegionOps snapshot_mmio_ops =3D { static void pci_snapshot_realize(PCIDevice *pdev, Error **errp) { SnapshotState *snapshot =3D SNAPSHOT(pdev); + snapshot->is_saved =3D false; + snapshot->ioc =3D NULL; =20 memory_region_init_io(&snapshot->mmio, OBJECT(snapshot), &snapshot_mmi= o_ops, snapshot, "snapshot-mmio", 1 * MiB); --=20 2.35.1