On 23/09/20 20:37, Sean Christopherson wrote:
> Patch 1 is a minor fix for a very theoretical bug where KVM could skip
> the final "commit zap" when recovering shadow pages for the NX huge
> page mitigation.
>
> Patch 2 is cleanup that's made possible by patch 1.
>
> Patches 3-5 are the main course and fix bugs in the NX huge page
> accounting where shadow pages are incorrectly added to the list of
> disallowed huge pages. KVM doesn't actually check to see if the page
> could actually have been a large page when adding to the disallowed list.
> This result in what are effectively spurious zaps. The biggest issue is
> likely with shadow pages in the upper levels, i.e. levels 3 and 4, as they
> are either unlikely to be huge (1gb) or flat out can't be huge (512tb).
> And because of the way KVM zaps, the upper levels will be zapped first,
> i.e. KVM is likely zapping and rebuilding a decent number of its shadow
> pages for zero benefit.
>
> Ideally, patches 3-5 would be a single patch to ease backporting. In the
> end, I decided the change is probably not suitable for stable as at worst
> it creates an infrequent performance spike (assuming the admin isn't going
> crazy with the recovery frequency), and it's far from straightforward or
> risk free. Cramming everything into a single patch was a mess.
>
> Patches 6-8 are cleanups in related code. The 'hlevel' name in particular
> has been on my todo list for a while.
>
> v2:
> - Rebased to kvm/queue, commit e1ba1a15af73 ("KVM: SVM: Enable INVPCID
> feature on AMD").
>
> Sean Christopherson (8):
> KVM: x86/mmu: Commit zap of remaining invalid pages when recovering
> lpages
> KVM: x86/mmu: Refactor the zap loop for recovering NX lpages
> KVM: x86/mmu: Move "huge page disallowed" calculation into mapping
> helpers
> KVM: x86/mmu: Capture requested page level before NX huge page
> workaround
> KVM: x86/mmu: Account NX huge page disallowed iff huge page was
> requested
> KVM: x86/mmu: Rename 'hlevel' to 'level' in FNAME(fetch)
> KVM: x86/mmu: Hoist ITLB multi-hit workaround check up a level
> KVM: x86/mmu: Track write/user faults using bools
>
> arch/x86/kvm/mmu/mmu.c | 58 +++++++++++++++++++++-------------
> arch/x86/kvm/mmu/paging_tmpl.h | 39 ++++++++++++-----------
> 2 files changed, 57 insertions(+), 40 deletions(-)
>
Queued, thanks.
Paolo
