Messages in this thread | | | Date | Fri, 17 Feb 2023 09:00:20 +0000 | From | Marc Zyngier <> | Subject | Re: [PATCH mm-unstable v1 3/5] kvm/arm64: add kvm_arch_test_clear_young() |
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On Fri, 17 Feb 2023 04:21:28 +0000, Yu Zhao <yuzhao@google.com> wrote: > > On Thu, Feb 16, 2023 at 9:12 PM Yu Zhao <yuzhao@google.com> wrote: > > > > This patch adds kvm_arch_test_clear_young() for the vast majority of > > VMs that are not pKVM and run on hardware that sets the accessed bit > > in KVM page tables.
I'm really interested in how you can back this statement. 90% of the HW I have access to is not FEAT_HWAFDB capable, either because it predates the feature or because the feature is too buggy to be useful.
Do you have numbers?
> > > > It relies on two techniques, RCU and cmpxchg, to safely test and clear > > the accessed bit without taking the MMU lock. The former protects KVM > > page tables from being freed while the latter clears the accessed bit > > atomically against both the hardware and other software page table > > walkers. > > > > Signed-off-by: Yu Zhao <yuzhao@google.com> > > --- > > arch/arm64/include/asm/kvm_host.h | 7 +++ > > arch/arm64/include/asm/kvm_pgtable.h | 8 +++ > > arch/arm64/include/asm/stage2_pgtable.h | 43 ++++++++++++++ > > arch/arm64/kvm/arm.c | 1 + > > arch/arm64/kvm/hyp/pgtable.c | 51 ++-------------- > > arch/arm64/kvm/mmu.c | 77 ++++++++++++++++++++++++- > > 6 files changed, 141 insertions(+), 46 deletions(-) > > Adding Marc and Will. > > Can you please add other interested parties that I've missed?
The MAINTAINERS file has it all:
KERNEL VIRTUAL MACHINE FOR ARM64 (KVM/arm64) M: Marc Zyngier <maz@kernel.org> M: Oliver Upton <oliver.upton@linux.dev> R: James Morse <james.morse@arm.com> R: Suzuki K Poulose <suzuki.poulose@arm.com> R: Zenghui Yu <yuzenghui@huawei.com> L: kvmarm@lists.linux.dev
May I suggest that you repost your patch and Cc the interested parties yourself? I guess most folks will want to see this in context, and not as a random, isolated change with no rationale.
M.
-- Without deviation from the norm, progress is not possible.
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