On 2/26/2026 9:59 PM, [email protected] wrote:
> From: Marc-André Lureau <[email protected]>
>
> Hi,
>
> This is an attempt to fix the incompatibility of virtio-mem with confidential
> VMs. The solution implements what was discussed earlier with D. Hildenbrand:
> https://patchwork.ozlabs.org/project/qemu-devel/patch/[email protected]/#3502238
>
> The first patches are misc cleanups. Then some code refactoring to have split
> a
> manager/source. And finally, the manager learns to deal with multiple sources.
>
> I haven't done thorough testing. I only launched a SEV guest with a virtio-mem
> device. It would be nice to have more tests for those scenarios with
> VFIO/virtio-mem/confvm.. In any case, review & testing needed!
Is this series aimed to enable virtio-mem (memory hotplug) in a confidential VM?
I tested it within a TD guest using the qemu command:
qemu-system-x86_64
...
-m 2G,maxmem=10G \
-smp sockets=1,cores=2 \
-object memory-backend-ram,id=mem0,size=2G \
-numa node,nodeid=0,cpus=0-1,memdev=mem0 \
-object memory-backend-ram,id=vmem0,size=8G \
-device virtio-mem-pci,id=vm0,memdev=vmem0,node=0,requested-size=300M \
-object tdx-guest,id=tdx \
-machine q35,kernel_irqchip=split,hpet=off,memory-encryption=tdx \
...
The TD VM will exit with the error when the guest kernel loads the virtio-mem
driver:
kvm_intel: Guest access before accepting 0x108008000 on vCPU 0
I think it still lacks some support to accept the TD guest memory before using
it.
>
> (should fix https://issues.redhat.com/browse/RHEL-131968)
>
> v3: issues found by Cédric
> - fix assertion error on shutdown, due to rcu-defer cleanup
> - fix API doc warnings
>
> v2:
> - drop replay_{populated,discarded} from source, suggested by Peter Xu
> - add extra manager cleanup
> - add r-b tags for preliminary patches
>
> thanks
>
> Marc-André Lureau (15):
> system/rba: use DIV_ROUND_UP
> memory: drop RamDiscardListener::double_discard_supported
> virtio-mem: use warn_report_err_once()
> system/memory: minor doc fix
> kvm: replace RamDicardManager by the RamBlockAttribute
> system/memory: split RamDiscardManager into source and manager
> system/memory: move RamDiscardManager to separate compilation unit
> system/memory: constify section arguments
> system/ram-discard-manager: implement replay via is_populated
> iteration
> virtio-mem: remove replay_populated/replay_discarded implementation
> system/ram-discard-manager: drop replay from source interface
> system/memory: implement RamDiscardManager multi-source aggregation
> system/physmem: destroy ram block attributes before RCU-deferred
> reclaim
> system/memory: add RamDiscardManager reference counting and cleanup
> tests: add unit tests for RamDiscardManager multi-source aggregation
>
> include/hw/vfio/vfio-container.h | 2 +-
> include/hw/vfio/vfio-cpr.h | 2 +-
> include/hw/virtio/virtio-mem.h | 3 -
> include/system/memory.h | 287 +----
> include/system/ram-discard-manager.h | 358 ++++++
> include/system/ramblock.h | 3 +-
> accel/kvm/kvm-all.c | 2 +-
> hw/vfio/cpr-legacy.c | 4 +-
> hw/vfio/listener.c | 12 +-
> hw/virtio/virtio-mem.c | 290 +----
> migration/ram.c | 6 +-
> system/memory.c | 83 +-
> system/memory_mapping.c | 4 +-
> system/physmem.c | 2 +-
> system/ram-block-attributes.c | 279 +----
> system/ram-discard-manager.c | 612 +++++++++
> tests/unit/test-ram-discard-manager-stubs.c | 48 +
> tests/unit/test-ram-discard-manager.c | 1234 +++++++++++++++++++
> system/meson.build | 1 +
> tests/unit/meson.build | 8 +-
> 20 files changed, 2361 insertions(+), 879 deletions(-)
> create mode 100644 include/system/ram-discard-manager.h
> create mode 100644 system/ram-discard-manager.c
> create mode 100644 tests/unit/test-ram-discard-manager-stubs.c
> create mode 100644 tests/unit/test-ram-discard-manager.c
>
