On Fri, 17 Feb 2023 04:21:28 +0000,
Yu Zhao <yuz...@google.com> wrote:
>
> On Thu, Feb 16, 2023 at 9:12 PM Yu Zhao <yuz...@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 <yuz...@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 <m...@kernel.org>
M: Oliver Upton <oliver.up...@linux.dev>
R: James Morse <james.mo...@arm.com>
R: Suzuki K Poulose <suzuki.poul...@arm.com>
R: Zenghui Yu <yuzeng...@huawei.com>
L: kvm...@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.
