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Re: [Xen-devel] [RFC v2 0/4] QEMU changes to do PVH boot
Hi Stefano,
[ Catching up on mail after vacation ]
On 03/01/2019 17:22, Stefano Garzarella wrote:
Hi Liam, Hi Maran,
I'm writing the optionrom to do PVH boot also with SeaBIOS.
It is almost complete and I'm testing it, but I have some issue with
QEMU -initrd parameter.
(It works correctly without -initrd and using a kernel with all needed
modules compiled statically)
Linux boots correctly, but it is not able to find the ramdisk. (I have
the same behavior with qboot)
Looking at Linux, QEMU, and qboot patches, I understood that the first
module pointed by 'modlist_paddr' in the 'hvm_start_info' should be
used to pass the ramdisk address and size to the kernel, but I didn't
understand who load it in RAM. (I guess QEMU directly or the firmware
by fw_cfg interface)
Can you give me some suggestions?
QEMU sets the hvm_modlist_entry in load_linux() after the call to
load_elfboot() and then qboot loads it in boot_pvh_from_fw_cfg()
But the current PVH patches don't handle initrd (they have
start_info.nr_modules == 1).
During (or after) the call to load_elfboot() it looks like we'd need to
do something like what load_multiboot() does below (along with the
associated initialisation)
400 fw_cfg_add_i32(fw_cfg, FW_CFG_INITRD_ADDR, ADDR_MBI);
401 fw_cfg_add_i32(fw_cfg, FW_CFG_INITRD_SIZE, sizeof(bootinfo));
402 fw_cfg_add_bytes(fw_cfg, FW_CFG_INITRD_DATA, mb_bootinfo_data,
403 sizeof(bootinfo));
I'm checking to see if that has any implications for the kernel side.
Regards,
Liam
On Fri, Dec 21, 2018 at 9:07 PM Liam Merwick <liam.merwick@xxxxxxxxxx> wrote:
For certain applications it is desirable to rapidly boot a KVM virtual
machine. In cases where legacy hardware and software support within the
guest is not needed, QEMU should be able to boot directly into the
uncompressed Linux kernel binary with minimal firmware involvement.
There already exists an ABI to allow this for Xen PVH guests and the ABI
is supported by Linux and FreeBSD:
https://xenbits.xen.org/docs/unstable/misc/pvh.html
Details on the Linux changes (v9 staged for 4.21):
https://lkml.org/lkml/2018/12/14/1330
qboot pull request: https://github.com/bonzini/qboot/pull/17
This patch series provides QEMU support to read the ELF header of an
uncompressed kernel binary and get the 32-bit PVH kernel entry point
from an ELF Note. In load_linux() a call is made to load_elfboot()
so see if the header matches that of an uncompressed kernel binary (ELF)
and if so, loads the binary and determines the kernel entry address
from an ELF Note in the binary. Then qboot does futher initialisation
of the guest (e820, etc.) and jumps to the kernel entry address and
boots the guest.
changes v1 -> v2
- Based on feedback from Stefan Hajnoczi
- The reading of the PVH entry point is now done in a single pass during
elf_load() which results in Patch2 in v1 being split into Patches 1&2 in v2
and considerably reworked.
- Patch1 adds a new optional function pointer to parse the ELF note type
(the type is passed in via the existing translate_opaque arg - the
function already had 11 args so I didn't want to add more than one new arg).
- Patch2 adds a function to elf_ops.h to find an ELF note
matching a specific type
- Patch3 just has a line added to the commit message to state that the Xen
repo is the canonical location
- Patch4 (that does the PVH boot) is mainly equivalent to Patch3 in v1
just minor load_elfboot() changes and the addition of a
read_pvh_start_addr() helper function for load_elf()
Usіng the method/scripts documented by the NEMU team at
https://github.com/intel/nemu/wiki/Measuring-Boot-Latency
https://lists.gnu.org/archive/html/qemu-devel/2018-12/msg00200.html
below are some timings measured (vmlinux and bzImage from the same build)
Time to get to kernel start is almost halved (95ṁs -> 48ms)
QEMU + qboot + vmlinux (PVH + 4.20-rc4)
qemu_init_end: 41.550521
fw_start: 41.667139 (+0.116618)
fw_do_boot: 47.448495 (+5.781356)
linux_startup_64: 47.720785 (+0.27229)
linux_start_kernel: 48.399541 (+0.678756)
linux_start_user: 296.952056 (+248.552515)
QEMU + qboot + bzImage:
qemu_init_end: 29.209276
fw_start: 29.317342 (+0.108066)
linux_start_boot: 36.679362 (+7.36202)
linux_startup_64: 94.531349 (+57.851987)
linux_start_kernel: 94.900913 (+0.369564)
linux_start_user: 401.060971 (+306.160058)
QEMU + bzImage:
qemu_init_end: 30.424430
linux_startup_64: 893.770334 (+863.345904)
linux_start_kernel: 894.17049 (+0.400156)
linux_start_user: 1208.679768 (+314.509278)
Liam Merwick (4):
elf: Add optional function ptr to load_elf() to parse ELF notes
elf-ops.h: Add get_elf_note_type()
pvh: Add x86/HVM direct boot ABI header file
pvh: Boot uncompressed kernel using direct boot ABI
hw/alpha/dp264.c | 4 +-
hw/arm/armv7m.c | 3 +-
hw/arm/boot.c | 2 +-
hw/core/generic-loader.c | 2 +-
hw/core/loader.c | 24 ++++---
hw/cris/boot.c | 3 +-
hw/hppa/machine.c | 6 +-
hw/i386/multiboot.c | 2 +-
hw/i386/pc.c | 131 +++++++++++++++++++++++++++++++++++-
hw/lm32/lm32_boards.c | 6 +-
hw/lm32/milkymist.c | 3 +-
hw/m68k/an5206.c | 2 +-
hw/m68k/mcf5208.c | 2 +-
hw/microblaze/boot.c | 7 +-
hw/mips/mips_fulong2e.c | 5 +-
hw/mips/mips_malta.c | 5 +-
hw/mips/mips_mipssim.c | 5 +-
hw/mips/mips_r4k.c | 5 +-
hw/moxie/moxiesim.c | 2 +-
hw/nios2/boot.c | 7 +-
hw/openrisc/openrisc_sim.c | 2 +-
hw/pci-host/prep.c | 2 +-
hw/ppc/e500.c | 3 +-
hw/ppc/mac_newworld.c | 5 +-
hw/ppc/mac_oldworld.c | 5 +-
hw/ppc/ppc440_bamboo.c | 2 +-
hw/ppc/sam460ex.c | 3 +-
hw/ppc/spapr.c | 7 +-
hw/ppc/virtex_ml507.c | 2 +-
hw/riscv/sifive_e.c | 2 +-
hw/riscv/sifive_u.c | 2 +-
hw/riscv/spike.c | 2 +-
hw/riscv/virt.c | 2 +-
hw/s390x/ipl.c | 9 ++-
hw/sparc/leon3.c | 3 +-
hw/sparc/sun4m.c | 6 +-
hw/sparc64/sun4u.c | 4 +-
hw/tricore/tricore_testboard.c | 2 +-
hw/xtensa/sim.c | 12 ++--
hw/xtensa/xtfpga.c | 2 +-
include/elf.h | 10 +++
include/hw/elf_ops.h | 72 ++++++++++++++++++++
include/hw/loader.h | 9 ++-
include/hw/xen/start_info.h | 146 +++++++++++++++++++++++++++++++++++++++++
44 files changed, 469 insertions(+), 71 deletions(-)
create mode 100644 include/hw/xen/start_info.h
--
1.8.3.1
--
Stefano Garzarella
Red Hat
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