Hello, This is another iteration of the virtio-pstore work. I've addressed all comments from Daniel Berrange on the qemu side. * changes in v4) - use qio_channel_file_new_path() (Daniel) - rename to delete_old_pstore_file (Daniel) - convert G_REMOVE_SOURCE to FALSE (Daniel) * changes in v3) - use QIOChannel API (Stefan, Daniel) - add bound check for malcious guests (Daniel) - drop support PSTORE_TYPE_CONSOLE for now - update license to allow GPL v2 or later (Michael) - limit number of pstore files on qemu * changes in v2) - update VIRTIO_ID_PSTORE to 22 (Cornelia, Stefan) - make buffer size configurable (Cornelia) - support PSTORE_TYPE_CONSOLE (Kees) - use separate virtqueues for read and write - support concurrent async write - manage pstore (file) id in device side - fix various mistakes in qemu device (Stefan) It started from the fact that dumping ftrace buffer at kernel oops/panic takes too much time. Although there's a way to reduce the size of the original data, sometimes I want to have the information as many as possible. Maybe kexec/kdump can solve this problem but it consumes some portion of guest memory so I'd like to avoid it. And I know the qemu + crashtool can dump and analyze the whole guest memory including the ftrace buffer without wasting guest memory, but it adds one more layer and has some limitation as an out-of-tree tool like not being in sync with the kernel changes. So I think it'd be great using the pstore interface to dump guest kernel data on the host. One can read the data on the host directly or on the guest (at the next boot) using pstore filesystem as usual. While this patchset only implements dumping kernel log buffer, it can be extended to have ftrace buffer and probably some more.. The patch 0001 implements virtio pstore driver. It has two virt queue for (sync) read and (async) write, pstore buffer and io request and response structure. The virtio_pstore_req struct is to give information about the current pstore operation. The result will be written to the virtio_pstore_res struct. For read operation it also uses virtio_pstore_fileinfo struct. The patch 0002 and 0003 implement virtio-pstore legacy PCI device on qemu-kvm and kvmtool respectively. I referenced virtio-baloon and virtio-rng implementations and I don't know whether kvmtool supports modern virtio 1.0+ spec. Other transports might be supported later. For example, using virtio-pstore on qemu looks like below: $ qemu-system-x86_64 -enable-kvm -device virtio-pstore,directory=xxx When guest kernel gets panic the log messages will be saved under the xxx directory. $ ls xxx dmesg-1.enc.z dmesg-2.enc.z As you can see the pstore subsystem compresses the log data using zlib (now supports lzo and lz4 too). The data can be extracted with the following command: $ cat xxx/dmesg-1.enc.z | \ > python -c 'import sys, zlib; print(zlib.decompress(sys.stdin.read()))' Oops#1 Part1 <5>[ 0.000000] Linux version 4.6.0kvm+ (namhyung@danjae) (gcc version 5.3.0 (GCC) ) #145 SMP Mon Jul 18 10:22:45 KST 2016 <6>[ 0.000000] Command line: root=/dev/vda console=ttyS0 <6>[ 0.000000] x86/fpu: Legacy x87 FPU detected. <6>[ 0.000000] x86/fpu: Using 'eager' FPU context switches. <6>[ 0.000000] e820: BIOS-provided physical RAM map: <6>[ 0.000000] BIOS-e820: [mem 0x0000000000000000-0x000000000009fbff] usable <6>[ 0.000000] BIOS-e820: [mem 0x000000000009fc00-0x000000000009ffff] reserved <6>[ 0.000000] BIOS-e820: [mem 0x00000000000f0000-0x00000000000fffff] reserved <6>[ 0.000000] BIOS-e820: [mem 0x0000000000100000-0x0000000007fddfff] usable <6>[ 0.000000] BIOS-e820: [mem 0x0000000007fde000-0x0000000007ffffff] reserved <6>[ 0.000000] BIOS-e820: [mem 0x00000000feffc000-0x00000000feffffff] reserved <6>[ 0.000000] BIOS-e820: [mem 0x00000000fffc0000-0x00000000ffffffff] reserved <6>[ 0.000000] NX (Execute Disable) protection: active <6>[ 0.000000] SMBIOS 2.8 present. <7>[ 0.000000] DMI: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.9.3-0-ge2fc41e-prebuilt.qemu-project.org 04/01/2014 ... Namhyung Kim (3): virtio: Basic implementation of virtio pstore driver qemu: Implement virtio-pstore device kvmtool: Implement virtio-pstore device drivers/virtio/Kconfig | 10 + drivers/virtio/Makefile | 1 + drivers/virtio/virtio_pstore.c | 417 +++++++++++++++++++++++++++++++++++++ include/uapi/linux/Kbuild | 1 + include/uapi/linux/virtio_ids.h | 1 + include/uapi/linux/virtio_pstore.h | 74 +++++++ 6 files changed, 504 insertions(+) create mode 100644 drivers/virtio/virtio_pstore.c create mode 100644 include/uapi/linux/virtio_pstore.h Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx> Cc: Radim Krčmář <rkrcmar@xxxxxxxxxx> Cc: "Michael S. Tsirkin" <mst@xxxxxxxxxx> Cc: Anthony Liguori <aliguori@xxxxxxxxxx> Cc: Anton Vorontsov <anton@xxxxxxxxxx> Cc: Colin Cross <ccross@xxxxxxxxxxx> Cc: Kees Cook <keescook@xxxxxxxxxxxx> Cc: Tony Luck <tony.luck@xxxxxxxxx> Cc: Steven Rostedt <rostedt@xxxxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxxxxx> Cc: Minchan Kim <minchan@xxxxxxxxxx> Cc: Will Deacon <will.deacon@xxxxxxx> Cc: kvm@xxxxxxxxxxxxxxx Cc: qemu-devel@xxxxxxxxxx Cc: virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx Cc: virtio-dev@xxxxxxxxxxxxxxxxxxxx Thanks, Namhyung -- 2.9.3 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
