On Mon, May 3, 2021 at 6:45 AM Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote: > > On 29/04/21 23:18, Ben Gardon wrote: > > This series enables KVM to save memory when using the TDP MMU by waiting > > to allocate memslot rmaps until they are needed. To do this, KVM tracks > > whether or not a shadow root has been allocated. In order to get away > > with not allocating the rmaps, KVM must also be sure to skip operations > > which iterate over the rmaps. If the TDP MMU is in use and we have not > > allocated a shadow root, these operations would essentially be op-ops > > anyway. Skipping the rmap operations has a secondary benefit of avoiding > > acquiring the MMU lock in write mode in many cases, substantially > > reducing MMU lock contention. > > > > This series was tested on an Intel Skylake machine. With the TDP MMU off > > and on, this introduced no new failures on kvm-unit-tests or KVM selftests. > > Thanks, I only reported some technicalities in the ordering of loads > (which matter since the loads happen with SRCU protection only). Apart > from this, this looks fine! Awesome to hear, thank you for the reviews. Should I send a v3 addressing those comments, or did you already make those changes when applying to your tree? > > Paolo > > > Changelog: > > v2: > > Incorporated feedback from Paolo and Sean > > Replaced the memslot_assignment_lock with slots_arch_lock, which > > has a larger critical section. > > > > Ben Gardon (7): > > KVM: x86/mmu: Track if shadow MMU active > > KVM: x86/mmu: Skip rmap operations if shadow MMU inactive > > KVM: x86/mmu: Deduplicate rmap freeing > > KVM: x86/mmu: Factor out allocating memslot rmap > > KVM: mmu: Refactor memslot copy > > KVM: mmu: Add slots_arch_lock for memslot arch fields > > KVM: x86/mmu: Lazily allocate memslot rmaps > > > > arch/x86/include/asm/kvm_host.h | 13 +++ > > arch/x86/kvm/mmu/mmu.c | 153 +++++++++++++++++++++----------- > > arch/x86/kvm/mmu/mmu_internal.h | 2 + > > arch/x86/kvm/mmu/tdp_mmu.c | 6 +- > > arch/x86/kvm/mmu/tdp_mmu.h | 4 +- > > arch/x86/kvm/x86.c | 110 +++++++++++++++++++---- > > include/linux/kvm_host.h | 9 ++ > > virt/kvm/kvm_main.c | 54 ++++++++--- > > 8 files changed, 264 insertions(+), 87 deletions(-) > > >
