v1: https://lore.kernel.org/r/20251023185913.2923322-1-peterx@redhat.com
v2: https://lore.kernel.org/r/20251119172913.577392-1-peterx@redhat.com
v3:
- Collect R-bs from Xiaoyao
- Rebased to 10.2-rc3; no dependency needed now, as those got merged
- Reorder patches, touch up commit messages or comments on in-place misuse
- Added patch "kvm: Provide explicit error for kvm_create_guest_memfd()" [Xiaoyao]
- Added one patch for renaming machine_require_guest_memfd() [Xiaoyao]
- Added one patch for renaming memory_region_init_ram_guest_memfd() [Xiaoyao]
=========8<===========
This series allows QEMU to consume init-shared guest-memfd to be a common
memory backend. Before this series, guest-memfd was only used in CoCo and
the fds will be created implicitly whenever CoCo environment is detected.
When used in init-shared mode, the guest-memfd will be specified in the
command lines directly just like other types of memory backends.
In the current patchset, I reused the memory-backend-memfd object, rather
than creating a new type of object. After all, guest-memfd (at least from
userspace POV) works similarly like a memfd, except that it was tailored
for VM's use case.
This approach so far also does not involve gmem bindings to KVM instances,
hence it is not prone to issues when the same chunk of RAM will be attached
to more than one KVM memslots.
Now, instead of using a normal memfd backend using:
-object memory-backend-memfd,id=ID,size=SIZE,share=on
One can also boot a VM with guest-memfd:
-object memory-backend-memfd,id=ID,size=SIZE,share=on,guest-memfd=on
The init-shared guest-memfd relies on almost the latest linux, as the
mmap() support just landed v6.18-rc2. When run it on an older qemu, we'll
see errors like:
qemu-system-x86_64: KVM does not support guest_memfd
One thing to mention is live migration is by default supported, however
postcopy is still currently not supported. The postcopy support will have
some kernel dependency work to be merged in Linux first.
Thanks,
Peter Xu (11):
kvm: Detect guest-memfd flags supported
kvm: Provide explicit error for kvm_create_guest_memfd()
ramblock: Rename guest_memfd to guest_memfd_private
memory: Rename RAM_GUEST_MEMFD to RAM_GUEST_MEMFD_PRIVATE
memory: Rename memory_region_has_guest_memfd() to *_private()
hostmem: Rename guest_memfd to guest_memfd_private
hostmem: Support fully shared guest memfd to back a VM
machine: Rename machine_require_guest_memfd() to *_private()
memory: Rename memory_region_init_ram_guest_memfd() to *_private()
tests/migration-test: Support guest-memfd init shared mem type
tests/migration-test: Add a precopy test for guest-memfd
Xiaoyao Li (1):
kvm: Decouple memory attribute check from kvm_guest_memfd_supported
qapi/qom.json | 6 ++-
include/hw/boards.h | 2 +-
include/system/hostmem.h | 2 +-
include/system/kvm.h | 1 +
include/system/memory.h | 27 ++++++------
include/system/ram_addr.h | 2 +-
include/system/ramblock.h | 7 +++-
tests/qtest/migration/framework.h | 4 ++
accel/kvm/kvm-all.c | 33 ++++++++++++---
accel/stubs/kvm-stub.c | 6 +++
backends/hostmem-file.c | 2 +-
backends/hostmem-memfd.c | 55 +++++++++++++++++++++---
backends/hostmem-ram.c | 2 +-
backends/hostmem-shm.c | 2 +-
backends/hostmem.c | 2 +-
backends/igvm.c | 4 +-
hw/core/machine.c | 2 +-
hw/i386/pc.c | 6 +--
hw/i386/pc_sysfw.c | 8 ++--
hw/i386/x86-common.c | 8 ++--
system/memory.c | 17 ++++----
system/physmem.c | 37 ++++++++++-------
target/i386/kvm/kvm.c | 3 +-
tests/qtest/migration/framework.c | 60 +++++++++++++++++++++++++++
tests/qtest/migration/precopy-tests.c | 12 ++++++
25 files changed, 239 insertions(+), 71 deletions(-)
--
2.50.1