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| author | Paolo Bonzini <pbonzini@redhat.com> | 2024-09-12 11:07:15 -0400 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2024-09-17 11:38:19 -0400 |
| commit | 55f50b2f86929ae042cd2eee8b2e8ffe00b5a885 (patch) | |
| tree | 233e06994cdde602da0703ba6ede84a503884ff7 /Documentation | |
| parent | 356dab4efd1a661c7882010c34594fe9cb0048f3 (diff) | |
| parent | 61de4c34b51c5b9c7ef8229eb246346254638446 (diff) | |
Merge branch 'kvm-memslot-zap-quirk' into HEAD
Today whenever a memslot is moved or deleted, KVM invalidates the entire
page tables and generates fresh ones based on the new memslot layout.
This behavior traditionally was kept because of a bug which was never
fully investigated and caused VM instability with assigned GeForce
GPUs. It generally does not have a huge overhead, because the old
MMU is able to reuse cached page tables and the new one is more
scalabale and can resolve EPT violations/nested page faults in parallel,
but it has worse performance if the guest frequently deletes and
adds small memslots, and it's entirely not viable for TDX. This is
because TDX requires re-accepting of private pages after page dropping.
For non-TDX VMs, this series therefore introduces the
KVM_X86_QUIRK_SLOT_ZAP_ALL quirk, enabling users to control the behavior
of memslot zapping when a memslot is moved/deleted. The quirk is turned
on by default, leading to the zapping of all SPTEs when a memslot is
moved/deleted; users however have the option to turn off the quirk,
which limits the zapping only to those SPTEs hat lie within the range
of memslot being moved/deleted.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/virt/kvm/api.rst | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index b3be87489108..b4d1cf2e4628 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -8082,6 +8082,14 @@ KVM_X86_QUIRK_MWAIT_NEVER_UD_FAULTS By default, KVM emulates MONITOR/MWAIT (if guest CPUID on writes to MISC_ENABLE if KVM_X86_QUIRK_MISC_ENABLE_NO_MWAIT is disabled. + +KVM_X86_QUIRK_SLOT_ZAP_ALL By default, KVM invalidates all SPTEs in + fast way for memslot deletion when VM type + is KVM_X86_DEFAULT_VM. + When this quirk is disabled or when VM type + is other than KVM_X86_DEFAULT_VM, KVM zaps + only leaf SPTEs that are within the range of + the memslot being deleted. =================================== ============================================ 7.32 KVM_CAP_MAX_VCPU_ID |