| Message ID | 20200108202448.9669-1-sean.j.christopherson@intel.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | KVM: x86/mmu: Huge page fixes, cleanup, and DAX | expand |
Hi - On 1/8/20 3:24 PM, Sean Christopherson wrote: > This series is a mix of bug fixes, cleanup and new support in KVM's > handling of huge pages. The series initially stemmed from a syzkaller > bug report[1], which is fixed by patch 02, "mm: thp: KVM: Explicitly > check for THP when populating secondary MMU". > > While investigating options for fixing the syzkaller bug, I realized KVM > could reuse the approach from Barret's series to enable huge pages for DAX > mappings in KVM[2] for all types of huge mappings, i.e. walk the host page > tables instead of querying metadata (patches 05 - 09). Thanks, Sean. I tested this patch series out, and it works for me. (Huge KVM mappings of a DAX file, etc.). Thanks, Barret
On 09/01/20 20:47, Barret Rhoden wrote: > Hi - > > On 1/8/20 3:24 PM, Sean Christopherson wrote: >> This series is a mix of bug fixes, cleanup and new support in KVM's >> handling of huge pages. The series initially stemmed from a syzkaller >> bug report[1], which is fixed by patch 02, "mm: thp: KVM: Explicitly >> check for THP when populating secondary MMU". >> >> While investigating options for fixing the syzkaller bug, I realized KVM >> could reuse the approach from Barret's series to enable huge pages for >> DAX >> mappings in KVM[2] for all types of huge mappings, i.e. walk the host >> page >> tables instead of querying metadata (patches 05 - 09). > > Thanks, Sean. I tested this patch series out, and it works for me. > (Huge KVM mappings of a DAX file, etc.). Queued, thanks. Paolo
This series is a mix of bug fixes, cleanup and new support in KVM's handling of huge pages. The series initially stemmed from a syzkaller bug report[1], which is fixed by patch 02, "mm: thp: KVM: Explicitly check for THP when populating secondary MMU". While investigating options for fixing the syzkaller bug, I realized KVM could reuse the approach from Barret's series to enable huge pages for DAX mappings in KVM[2] for all types of huge mappings, i.e. walk the host page tables instead of querying metadata (patches 05 - 09). Walking the host page tables sidesteps the issues with refcounting and identifying THP mappings (in theory), and using a common method for identifying huge mappings should improve (haven't actually measured) KVM's overall page fault latency by eliminating the vma lookup that is currently used to identify HugeTLB mappings. Eliminating the HugeTLB specific code also allows for additional cleanup (patches 10 - 13). Testing the page walk approach revealed several pre-existing bugs that are included here (patches 01, 03 and 04) because the changes interact with the rest of the series, e.g. without the read-only memslots fix, walking the host page tables without explicitly filtering out HugeTLB mappings would pick up read-only memslots and introduce a completely unintended functional change. Lastly, with the page walk infrastructure in place, supporting DAX-based huge mappings becomes a trivial change (patch 14). Based on kvm/queue, commit e41a90be9659 ("KVM: x86/mmu: WARN if root_hpa is invalid when handling a page fault") Paolo, assuming I understand your workflow, patch 01 can be squashed with the buggy commit as it's still sitting in kvm/queue. [1] https://lkml.kernel.org/r/0000000000003cffc30599d3d1a0@google.com [2] https://lkml.kernel.org/r/20191212182238.46535-1-brho@google.com Sean Christopherson (14): KVM: x86/mmu: Enforce max_level on HugeTLB mappings mm: thp: KVM: Explicitly check for THP when populating secondary MMU KVM: Use vcpu-specific gva->hva translation when querying host page size KVM: Play nice with read-only memslots when querying host page size x86/mm: Introduce lookup_address_in_mm() KVM: x86/mmu: Refactor THP adjust to prep for changing query KVM: x86/mmu: Walk host page tables to find THP mappings KVM: x86/mmu: Drop level optimization from fast_page_fault() KVM: x86/mmu: Rely on host page tables to find HugeTLB mappings KVM: x86/mmu: Remove obsolete gfn restoration in FNAME(fetch) KVM: x86/mmu: Zap any compound page when collapsing sptes KVM: x86/mmu: Fold max_mapping_level() into kvm_mmu_hugepage_adjust() KVM: x86/mmu: Remove lpage_is_disallowed() check from set_spte() KVM: x86/mmu: Use huge pages for DAX-backed files arch/powerpc/kvm/book3s_xive_native.c | 2 +- arch/x86/include/asm/pgtable_types.h | 4 + arch/x86/kvm/mmu/mmu.c | 208 ++++++++++---------------- arch/x86/kvm/mmu/paging_tmpl.h | 29 +--- arch/x86/mm/pageattr.c | 11 ++ include/linux/huge_mm.h | 6 + include/linux/kvm_host.h | 3 +- mm/huge_memory.c | 11 ++ virt/kvm/arm/mmu.c | 8 +- virt/kvm/kvm_main.c | 24 ++- 10 files changed, 145 insertions(+), 161 deletions(-)