v2: https://lore.kernel.org/kvm/20230118145030.40845-1-minipli@xxxxxxxxxxxxxx/ This series is a resurrection of the missing pieces of Paolo's previous attempt[1] to avoid needless MMU roots unloading. The performance gap between TDP and legacy MMU is still existent, especially noticeable under grsecurity which implements kernel W^X by toggling CR0.WP, which happens very frequently. Patches 1-13 and 17 of the old series had been merged, but, unfortunately, the remaining parts never saw a v3. I therefore took care of these, took Sean's feedback into account[2] and simplified the whole approach to just handle the case we care most about explicitly. Patch 1 is a v3 of [3], addressing Sean's feedback. Patch 2 is specifically useful for grsecurity, as handle_cr() is by far *the* top vmexit reason. Patch 3 is the most important one, as it skips unloading the MMU roots for CR0.WP toggling. Sean was suggesting another change on top of v2 of this series, to skip intercepting CR0.WP writes completely for VMX[4]. That turned out to be yet another performance boost and is implemenmted in patch 6. While patches 1 and 2 bring small performance improvements already, the big gains come from patches 3 and 6. I used 'ssdd 10 50000' from rt-tests[5] as a micro-benchmark, running on a grsecurity L1 VM. Below table shows the results (runtime in seconds, lower is better): legacy TDP shadow kvm.git/queue 11.55s 13.91s 75.2s + patches 1-3 7.32s 7.31s 74.6s + patches 4-6 4.89s 4.89s 73.4s This series builds on top of kvm.git/queue, namely commit de60733246ff ("Merge branch 'kvm-hw-enable-refactor' into HEAD"). Patches 1-3 didn't change from v2, beside minor changlog mangling. Patches 4-6 are new to v3. Thanks, Mathias [1] https://lore.kernel.org/kvm/20220217210340.312449-1-pbonzini@xxxxxxxxxx/ [2] https://lore.kernel.org/kvm/YhATewkkO%2Fl4P9UN@xxxxxxxxxx/ [3] https://lore.kernel.org/kvm/YhAB1d1%2FnQbx6yvk@xxxxxxxxxx/ [4] https://lore.kernel.org/kvm/Y8cTMnyBzNdO5dY3@xxxxxxxxxx/ [5] https://git.kernel.org/pub/scm/utils/rt-tests/rt-tests.git Mathias Krause (5): KVM: VMX: Avoid retpoline call for control register caused exits KVM: x86: Do not unload MMU roots when only toggling CR0.WP KVM: x86: Make use of kvm_read_cr*_bits() when testing bits KVM: x86/mmu: Fix comment typo KVM: VMX: Make CR0.WP a guest owned bit Paolo Bonzini (1): KVM: x86/mmu: Avoid indirect call for get_cr3 arch/x86/kvm/kvm_cache_regs.h | 3 ++- arch/x86/kvm/mmu/mmu.c | 31 ++++++++++++++++++++----------- arch/x86/kvm/mmu/paging_tmpl.h | 2 +- arch/x86/kvm/mmu/spte.c | 2 +- arch/x86/kvm/pmu.c | 4 ++-- arch/x86/kvm/vmx/capabilities.h | 1 + arch/x86/kvm/vmx/nested.c | 4 ++-- arch/x86/kvm/vmx/vmx.c | 15 ++++++++++++--- arch/x86/kvm/vmx/vmx.h | 8 ++++++++ arch/x86/kvm/x86.c | 9 +++++++++ 10 files changed, 58 insertions(+), 21 deletions(-) -- 2.39.1
