From 8191d3684157884bf7e6eff0d247d7e91a1cc543 Mon Sep 17 00:00:00 2001 From: Claudio Fontana Date: Mon, 31 Aug 2020 16:18:34 +0200 Subject: icount: rename functions to be consistent with the module name Signed-off-by: Claudio Fontana Reviewed-by: Richard Henderson Reviewed-by: Alex Bennée Signed-off-by: Paolo Bonzini --- docs/replay.txt | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'docs') diff --git a/docs/replay.txt b/docs/replay.txt index 70c27edb36..8952e6d852 100644 --- a/docs/replay.txt +++ b/docs/replay.txt @@ -184,11 +184,11 @@ is then incremented (which is called "warping" the virtual clock) as soon as the timer fires or the CPUs need to go out of the idle state. Two functions are used for this purpose; because these actions change virtual machine state and must be deterministic, each of them creates a -checkpoint. qemu_start_warp_timer checks if the CPUs are idle and if so -starts accounting real time to virtual clock. qemu_account_warp_timer +checkpoint. icount_start_warp_timer checks if the CPUs are idle and if so +starts accounting real time to virtual clock. icount_account_warp_timer is called when the CPUs get an interrupt or when the warp timer fires, and it warps the virtual clock by the amount of real time that has passed -since qemu_start_warp_timer. +since icount_start_warp_timer. Bottom halves ------------- -- cgit v1.2.3-55-g7522 From bbacffc5f7a1a9318afe62f4eb20b3584acb6aa1 Mon Sep 17 00:00:00 2001 From: Pavel Dovgalyuk Date: Sat, 3 Oct 2020 20:13:02 +0300 Subject: qcow2: introduce icount field for snapshots This patch introduces the icount field for saving within the snapshot. It is required for navigation between the snapshots in record/replay mode. Signed-off-by: Pavel Dovgalyuk Acked-by: Kevin Wolf -- v7 changes: - also fix the test which checks qcow2 snapshot extra data Message-Id: <160174518284.12451.2301137308458777398.stgit@pasha-ThinkPad-X280> Signed-off-by: Paolo Bonzini --- block/qcow2-snapshot.c | 7 +++++++ block/qcow2.h | 3 +++ docs/interop/qcow2.txt | 5 +++++ tests/qemu-iotests/261 | 15 ++++++++------ tests/qemu-iotests/261.out | 51 ++++++++++++++++++++++++++++++---------------- 5 files changed, 58 insertions(+), 23 deletions(-) (limited to 'docs') diff --git a/block/qcow2-snapshot.c b/block/qcow2-snapshot.c index 9b68690f56..d68b25e0c5 100644 --- a/block/qcow2-snapshot.c +++ b/block/qcow2-snapshot.c @@ -164,6 +164,12 @@ static int qcow2_do_read_snapshots(BlockDriverState *bs, bool repair, sn->disk_size = bs->total_sectors * BDRV_SECTOR_SIZE; } + if (sn->extra_data_size >= endof(QCowSnapshotExtraData, icount)) { + sn->icount = be64_to_cpu(extra.icount); + } else { + sn->icount = -1ULL; + } + if (sn->extra_data_size > sizeof(extra)) { uint64_t extra_data_end; size_t unknown_extra_data_size; @@ -333,6 +339,7 @@ int qcow2_write_snapshots(BlockDriverState *bs) memset(&extra, 0, sizeof(extra)); extra.vm_state_size_large = cpu_to_be64(sn->vm_state_size); extra.disk_size = cpu_to_be64(sn->disk_size); + extra.icount = cpu_to_be64(sn->icount); id_str_size = strlen(sn->id_str); name_size = strlen(sn->name); diff --git a/block/qcow2.h b/block/qcow2.h index b71e444fca..125ea9679b 100644 --- a/block/qcow2.h +++ b/block/qcow2.h @@ -206,6 +206,7 @@ typedef struct QEMU_PACKED QCowSnapshotHeader { typedef struct QEMU_PACKED QCowSnapshotExtraData { uint64_t vm_state_size_large; uint64_t disk_size; + uint64_t icount; } QCowSnapshotExtraData; @@ -219,6 +220,8 @@ typedef struct QCowSnapshot { uint32_t date_sec; uint32_t date_nsec; uint64_t vm_clock_nsec; + /* icount value for the moment when snapshot was taken */ + uint64_t icount; /* Size of all extra data, including QCowSnapshotExtraData if available */ uint32_t extra_data_size; /* Data beyond QCowSnapshotExtraData, if any */ diff --git a/docs/interop/qcow2.txt b/docs/interop/qcow2.txt index 7da0d81df8..0463f761ef 100644 --- a/docs/interop/qcow2.txt +++ b/docs/interop/qcow2.txt @@ -707,6 +707,11 @@ Snapshot table entry: Byte 48 - 55: Virtual disk size of the snapshot in bytes + Byte 56 - 63: icount value which corresponds to + the record/replay instruction count + when the snapshot was taken. Set to -1 + if icount was disabled + Version 3 images must include extra data at least up to byte 55. diff --git a/tests/qemu-iotests/261 b/tests/qemu-iotests/261 index ddcb04f285..848ffa760d 100755 --- a/tests/qemu-iotests/261 +++ b/tests/qemu-iotests/261 @@ -91,7 +91,10 @@ print_snapshot_table() if [ $extra_len -ge 16 ]; then echo " Disk size: $(peek_file_be "$1" $((extra_ofs + 8)) 8)" fi - if [ $extra_len -gt 16 ]; then + if [ $extra_len -ge 24 ]; then + echo " Icount: $(peek_file_be "$1" $((extra_ofs + 16)) 8)" + fi + if [ $extra_len -gt 24 ]; then echo ' Unknown extra data:' \ "$(peek_file_raw "$1" $((extra_ofs + 16)) $((extra_len - 16)) \ | tr -d '\0')" @@ -198,12 +201,12 @@ truncate -s 0 "$TEST_DIR/sn0-extra" truncate -s $(($(snapshot_table_entry_size "$TEST_DIR/sn0-pre") - 40)) \ "$TEST_DIR/sn0-post" -# Set sn1's extra data size to 42 -poke_file "$TEST_DIR/sn1-pre" 36 '\x00\x00\x00\x2a' -truncate -s 42 "$TEST_DIR/sn1-extra" -poke_file "$TEST_DIR/sn1-extra" 16 'very important data' +# Set sn1's extra data size to 50 +poke_file "$TEST_DIR/sn1-pre" 36 '\x00\x00\x00\x32' +truncate -s 50 "$TEST_DIR/sn1-extra" +poke_file "$TEST_DIR/sn1-extra" 24 'very important data' # Grow sn1-post to pad -truncate -s $(($(snapshot_table_entry_size "$TEST_DIR/sn1-pre") - 82)) \ +truncate -s $(($(snapshot_table_entry_size "$TEST_DIR/sn1-pre") - 90)) \ "$TEST_DIR/sn1-post" # Set sn2's extra data size to 8 diff --git a/tests/qemu-iotests/261.out b/tests/qemu-iotests/261.out index 2600354566..612433ae40 100644 --- a/tests/qemu-iotests/261.out +++ b/tests/qemu-iotests/261.out @@ -12,9 +12,10 @@ Snapshots in TEST_DIR/t.IMGFMT.v2.orig: [1] ID: 2 Name: sn1 - Extra data size: 42 + Extra data size: 50 VM state size: 0 Disk size: 67108864 + Icount: 0 Unknown extra data: very important data [2] ID: 3 @@ -29,22 +30,25 @@ Snapshots in TEST_DIR/t.IMGFMT.v3.orig: [0] ID: 1 Name: sn0 - Extra data size: 16 + Extra data size: 24 VM state size: 0 Disk size: 67108864 + Icount: 18446744073709551615 [1] ID: 2 Name: sn1 - Extra data size: 42 + Extra data size: 50 VM state size: 0 Disk size: 67108864 + Icount: 0 Unknown extra data: very important data [2] ID: 3 Name: sn2 - Extra data size: 16 + Extra data size: 24 VM state size: 0 Disk size: 67108864 + Icount: 18446744073709551615 === Repair botched v3 === @@ -61,22 +65,25 @@ Snapshots in TEST_DIR/t.IMGFMT: [0] ID: 1 Name: sn0 - Extra data size: 16 + Extra data size: 24 VM state size: 0 Disk size: 67108864 + Icount: 18446744073709551615 [1] ID: 2 Name: sn1 - Extra data size: 42 + Extra data size: 50 VM state size: 0 Disk size: 67108864 + Icount: 0 Unknown extra data: very important data [2] ID: 3 Name: sn2 - Extra data size: 16 + Extra data size: 24 VM state size: 0 Disk size: 67108864 + Icount: 18446744073709551615 === Add new snapshot === @@ -85,28 +92,32 @@ Snapshots in TEST_DIR/t.IMGFMT: [0] ID: 1 Name: sn0 - Extra data size: 16 + Extra data size: 24 VM state size: 0 Disk size: 67108864 + Icount: 18446744073709551615 [1] ID: 2 Name: sn1 - Extra data size: 42 + Extra data size: 50 VM state size: 0 Disk size: 67108864 + Icount: 0 Unknown extra data: very important data [2] ID: 3 Name: sn2 - Extra data size: 16 + Extra data size: 24 VM state size: 0 Disk size: 67108864 + Icount: 18446744073709551615 [3] ID: 4 Name: sn3 - Extra data size: 16 + Extra data size: 24 VM state size: 0 Disk size: 67108864 + Icount: 0 === Remove different snapshots === @@ -116,16 +127,18 @@ Snapshots in TEST_DIR/t.IMGFMT: [0] ID: 2 Name: sn1 - Extra data size: 42 + Extra data size: 50 VM state size: 0 Disk size: 67108864 + Icount: 0 Unknown extra data: very important data [1] ID: 3 Name: sn2 - Extra data size: 16 + Extra data size: 24 VM state size: 0 Disk size: 67108864 + Icount: 18446744073709551615 --- sn1 --- No errors were found on the image. @@ -133,15 +146,17 @@ Snapshots in TEST_DIR/t.IMGFMT: [0] ID: 1 Name: sn0 - Extra data size: 16 + Extra data size: 24 VM state size: 0 Disk size: 67108864 + Icount: 18446744073709551615 [1] ID: 3 Name: sn2 - Extra data size: 16 + Extra data size: 24 VM state size: 0 Disk size: 67108864 + Icount: 18446744073709551615 --- sn2 --- No errors were found on the image. @@ -149,15 +164,17 @@ Snapshots in TEST_DIR/t.IMGFMT: [0] ID: 1 Name: sn0 - Extra data size: 16 + Extra data size: 24 VM state size: 0 Disk size: 67108864 + Icount: 18446744073709551615 [1] ID: 2 Name: sn1 - Extra data size: 42 + Extra data size: 50 VM state size: 0 Disk size: 67108864 + Icount: 0 Unknown extra data: very important data === Reject too much unknown extra data === -- cgit v1.2.3-55-g7522 From 9a608af3c0f9856e396d12c3ec8985d70c548a54 Mon Sep 17 00:00:00 2001 From: Pavel Dovgalyuk Date: Sat, 3 Oct 2020 20:13:55 +0300 Subject: replay: describe reverse debugging in docs/replay.txt This patch updates the documentation and describes usage of the reverse debugging in QEMU+GDB. Signed-off-by: Pavel Dovgalyuk Reviewed-by: Alex Bennée -- v4 changes: - added an example of the command line for reverse debugging of the diskless machine Message-Id: <160174523509.12451.1409905901920738979.stgit@pasha-ThinkPad-X280> Signed-off-by: Paolo Bonzini --- docs/replay.txt | 46 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 46 insertions(+) (limited to 'docs') diff --git a/docs/replay.txt b/docs/replay.txt index 8952e6d852..87a64ae068 100644 --- a/docs/replay.txt +++ b/docs/replay.txt @@ -265,6 +265,16 @@ of the original disk image, use overlay files linked to the original images. Therefore all new snapshots (including the starting one) will be saved in overlays and the original image remains unchanged. +When you need to use snapshots with diskless virtual machine, +it must be started with 'orphan' qcow2 image. This image will be used +for storing VM snapshots. Here is the example of the command line for this: + + qemu-system-i386 -icount shift=3,rr=replay,rrfile=record.bin,rrsnapshot=init \ + -net none -drive file=empty.qcow2,if=none,id=rr + +empty.qcow2 drive does not connected to any virtual block device and used +for VM snapshots only. + Network devices --------------- @@ -294,6 +304,42 @@ for recording and replaying must contain identical number of ports in record and replay modes, but their backends may differ. E.g., '-serial stdio' in record mode, and '-serial null' in replay mode. +Reverse debugging +----------------- + +Reverse debugging allows "executing" the program in reverse direction. +GDB remote protocol supports "reverse step" and "reverse continue" +commands. The first one steps single instruction backwards in time, +and the second one finds the last breakpoint in the past. + +Recorded executions may be used to enable reverse debugging. QEMU can't +execute the code in backwards direction, but can load a snapshot and +replay forward to find the desired position or breakpoint. + +The following GDB commands are supported: + - reverse-stepi (or rsi) - step one instruction backwards + - reverse-continue (or rc) - find last breakpoint in the past + +Reverse step loads the nearest snapshot and replays the execution until +the required instruction is met. + +Reverse continue may include several passes of examining the execution +between the snapshots. Each of the passes include the following steps: + 1. loading the snapshot + 2. replaying to examine the breakpoints + 3. if breakpoint or watchpoint was met + - loading the snaphot again + - replaying to the required breakpoint + 4. else + - proceeding to the p.1 with the earlier snapshot + +Therefore usage of the reverse debugging requires at least one snapshot +created in advance. This can be done by omitting 'snapshot' option +for the block drives and adding 'rrsnapshot' for both record and replay +command lines. +See the "Snapshotting" section to learn more about running record/replay +and creating the snapshot in these modes. + Replay log format ----------------- -- cgit v1.2.3-55-g7522