Re: [GIT PULL] KVM/arm64 fixes for 6.3, part #2

[Marc Zyngier <maz@kernel.org>]

On Fri, 24 Mar 2023 18:16:30 +0000,
Oliver Upton <oliver.upton@linux.dev> wrote:
> 
> Paolo,
> 
> Pinging this PR in case you missed it, the issues around host page table walks
> are particularly urgent as the race on host page table teardown has been
> reproduced on some setups.

If we don't hear from Paolo shortly, I suggest we route this via the
arm64 tree.

Thanks,

	M.

> 
> --
> Thanks,
> Oliver
> 
> On Thu, Mar 16, 2023 at 08:09:20PM -0700, Oliver Upton wrote:
> > Hi Paolo,
> > 
> > Another week, another set of fixes for KVM/arm64.
> > 
> > Description can be found in the tag, but the teardown race when walking
> > host page tables is particularly nasty and currently causing problems
> > for folks. The fix is quite simple by disabling interrupts when walking
> > host page tables, as the thread must be IPI'ed before the table memory
> > can actually be freed.
> > 
> > Please pull,
> > 
> > Oliver
> > 
> > The following changes since commit 47053904e18282af4525a02e3e0f519f014fc7f9:
> > 
> >   KVM: arm64: timers: Convert per-vcpu virtual offset to a global value (2023-03-11 02:00:40 -0800)
> > 
> > are available in the Git repository at:
> > 
> >   git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git tags/kvmarm-fixes-6.3-2
> > 
> > for you to fetch changes up to 8c2e8ac8ad4be68409e806ce1cc78fc7a04539f3:
> > 
> >   KVM: arm64: Check for kvm_vma_mte_allowed in the critical section (2023-03-16 23:42:56 +0000)
> > 
> > ----------------------------------------------------------------
> > KVM/arm64 fixes for 6.3, part #2
> > 
> > Fixes for a rather interesting set of bugs relating to the MMU:
> > 
> >  - Read the MMU notifier seq before dropping the mmap lock to guard
> >    against reading a potentially stale VMA
> > 
> >  - Disable interrupts when walking user page tables to protect against
> >    the page table being freed
> > 
> >  - Read the MTE permissions for the VMA within the mmap lock critical
> >    section, avoiding the use of a potentally stale VMA pointer
> > 
> > Additionally, some fixes targeting the vPMU:
> > 
> >  - Return the sum of the current perf event value and PMC snapshot for
> >    reads from userspace
> > 
> >  - Don't save the value of guest writes to PMCR_EL0.{C,P}, which could
> >    otherwise lead to userspace erroneously resetting the vPMU during VM
> >    save/restore
> > 
> > ----------------------------------------------------------------
> > David Matlack (1):
> >       KVM: arm64: Retry fault if vma_lookup() results become invalid
> > 
> > Marc Zyngier (2):
> >       KVM: arm64: Disable interrupts while walking userspace PTs
> >       KVM: arm64: Check for kvm_vma_mte_allowed in the critical section
> > 
> > Reiji Watanabe (2):
> >       KVM: arm64: PMU: Fix GET_ONE_REG for vPMC regs to return the current value
> >       KVM: arm64: PMU: Don't save PMCR_EL0.{C,P} for the vCPU
> > 
> >  arch/arm64/kvm/mmu.c      | 99 ++++++++++++++++++++++++++++++-----------------
> >  arch/arm64/kvm/pmu-emul.c |  3 +-
> >  arch/arm64/kvm/sys_regs.c | 21 +++++++++-
> >  3 files changed, 85 insertions(+), 38 deletions(-)
> > 
> 
> -- 
> Thanks,
> Oliver
> 

-- 
Without deviation from the norm, progress is not possible.