[Same distribution list as Gavin's dirty-ring on arm64 series] As Gavin started posting patches enabling the dirty-ring infrastructure on arm64 [1], it quickly became apparent that the API was never intended to work on relaxed memory ordering architectures (owing to its x86 origins). This series tries to retrofit some ordering into the existing API by: - relying on acquire/release semantics which are the default on x86, but need to be explicit on arm64 - adding a new capability that indicate which flavor is supported, either with explicit ordering (arm64) or both implicit and explicit (x86), as suggested by Paolo at KVM Forum - documenting the requirements for this new capability on weakly ordered architectures - updating the selftests to do the right thing Ideally, this series should be a prefix of Gavin's, plus a small change to his series: diff --git a/arch/arm64/kvm/Kconfig b/arch/arm64/kvm/Kconfig index 0309b2d0f2da..7785379c5048 100644 --- a/arch/arm64/kvm/Kconfig +++ b/arch/arm64/kvm/Kconfig @@ -32,7 +32,7 @@ menuconfig KVM select KVM_VFIO select HAVE_KVM_EVENTFD select HAVE_KVM_IRQFD - select HAVE_KVM_DIRTY_RING + select HAVE_KVM_DIRTY_RING_ORDERED select HAVE_KVM_MSI select HAVE_KVM_IRQCHIP select HAVE_KVM_IRQ_ROUTING This has been very lightly tested on an arm64 box with Gavin's v3 [2] series. [1] https://lore.kernel.org/lkml/YyiV%2Fl7O23aw5aaO@xz-m1.local/T/ [2] https://lore.kernel.org/r/20220922003214.276736-1-gshan@xxxxxxxxxx Marc Zyngier (6): KVM: Use acquire/release semantics when accessing dirty ring GFN state KVM: Add KVM_CAP_DIRTY_LOG_RING_ORDERED capability and config option KVM: x86: Select CONFIG_HAVE_KVM_DIRTY_RING_ORDERED KVM: Document weakly ordered architecture requirements for dirty ring KVM: selftests: dirty-log: Upgrade dirty_gfn_set_collected() to store-release KVM: selftests: dirty-log: Use KVM_CAP_DIRTY_LOG_RING_ORDERED of available Documentation/virt/kvm/api.rst | 16 +++++++++++++--- arch/x86/kvm/Kconfig | 1 + include/linux/kvm_dirty_ring.h | 6 +++--- include/uapi/linux/kvm.h | 1 + tools/testing/selftests/kvm/dirty_log_test.c | 6 ++++-- tools/testing/selftests/kvm/lib/kvm_util.c | 5 ++++- virt/kvm/Kconfig | 14 ++++++++++++++ virt/kvm/Makefile.kvm | 2 +- virt/kvm/dirty_ring.c | 4 ++-- virt/kvm/kvm_main.c | 11 +++++++++-- 10 files changed, 52 insertions(+), 14 deletions(-) -- 2.34.1
