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Date:   Thu, 10 Mar 2022 08:45:19 -0800
Message-Id: <20220310164532.1821490-1-bgardon@google.com>
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Subject: [PATCH 00/13] KVM: x86: Add a cap to disable NX hugepages on a VM
From:   Ben Gardon <bgardon@google.com>
To:     linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Cc:     Paolo Bonzini <pbonzini@redhat.com>, Peter Xu <peterx@redhat.com>,
        Sean Christopherson <seanjc@google.com>,
        David Matlack <dmatlack@google.com>,
        Jim Mattson <jmattson@google.com>,
        David Dunn <daviddunn@google.com>,
        Jing Zhang <jingzhangos@google.com>,
        Junaid Shahid <junaids@google.com>,
        Ben Gardon <bgardon@google.com>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

Given the high cost of NX hugepages in terms of TLB performance, it may
be desirable to disable the mitigation on a per-VM basis. In the case of public
cloud providers with many VMs on a single host, some VMs may be more trusted
than others. In order to maximize performance on critical VMs, while still
providing some protection to the host from iTLB Multihit, allow the mitigation
to be selectively disabled.

Disabling NX hugepages on a VM is relatively straightforward, but I took this
as an opportunity to add some NX hugepages test coverage and clean up selftests
infrastructure a bit.

Patches 1-2 add some library calls for accessing stats via the binary stats API.
Patches 3-5 improve memslot ID handling in the KVM util library.
Patch 6 is a misc logging improvement.
Patches 7 and 13 implement an NX hugepages test.
Patches 8, 9, 10, and 12 implement disabling NX on a VM.
Patch 11 is a small cleanup of a bad merge.

This series was tested with the new selftest and the rest of the KVM selftests
on an Intel Haswell machine.

The following tests failed, but I do not believe that has anything to do with
this series:
	userspace_io_test
	vmx_nested_tsc_scaling_test
	vmx_preemption_timer_test

Ben Gardon (13):
  selftests: KVM: Dump VM stats in binary stats test
  selftests: KVM: Test reading a single stat
  selftests: KVM: Wrap memslot IDs in a struct for readability
  selftests: KVM: Add memslot parameter to VM vaddr allocation
  selftests: KVM: Add memslot parameter to elf_load
  selftests: KVM: Improve error message in vm_phy_pages_alloc
  selftests: KVM: Add NX huge pages test
  KVM: x86/MMU: Factor out updating NX hugepages state for a VM
  KVM: x86/MMU: Track NX hugepages on a per-VM basis
  KVM: x86/MMU: Allow NX huge pages to be disabled on a per-vm basis
  KVM: x86: Fix errant brace in KVM capability handling
  KVM: x86/MMU: Require reboot permission to disable NX hugepages
  selftests: KVM: Test disabling NX hugepages on a VM

 arch/x86/include/asm/kvm_host.h               |   3 +
 arch/x86/kvm/mmu.h                            |   9 +-
 arch/x86/kvm/mmu/mmu.c                        |  23 +-
 arch/x86/kvm/mmu/spte.c                       |   7 +-
 arch/x86/kvm/mmu/spte.h                       |   3 +-
 arch/x86/kvm/mmu/tdp_mmu.c                    |   3 +-
 arch/x86/kvm/x86.c                            |  24 +-
 include/uapi/linux/kvm.h                      |   1 +
 tools/testing/selftests/kvm/Makefile          |   3 +-
 .../selftests/kvm/aarch64/psci_cpu_on_test.c  |   2 +-
 .../selftests/kvm/dirty_log_perf_test.c       |   7 +-
 tools/testing/selftests/kvm/dirty_log_test.c  |  45 +--
 .../selftests/kvm/hardware_disable_test.c     |   2 +-
 .../selftests/kvm/include/kvm_util_base.h     |  57 ++--
 .../selftests/kvm/include/x86_64/vmx.h        |   4 +-
 .../selftests/kvm/kvm_binary_stats_test.c     |   6 +
 .../selftests/kvm/kvm_page_table_test.c       |   9 +-
 .../selftests/kvm/lib/aarch64/processor.c     |   7 +-
 tools/testing/selftests/kvm/lib/elf.c         |   5 +-
 tools/testing/selftests/kvm/lib/kvm_util.c    | 311 +++++++++++++++---
 .../selftests/kvm/lib/kvm_util_internal.h     |   2 +-
 .../selftests/kvm/lib/perf_test_util.c        |   4 +-
 .../selftests/kvm/lib/riscv/processor.c       |   5 +-
 .../selftests/kvm/lib/s390x/processor.c       |   9 +-
 .../kvm/lib/x86_64/nx_huge_pages_guest.S      |  45 +++
 .../selftests/kvm/lib/x86_64/processor.c      |  11 +-
 tools/testing/selftests/kvm/lib/x86_64/svm.c  |   8 +-
 tools/testing/selftests/kvm/lib/x86_64/vmx.c  |  26 +-
 .../selftests/kvm/max_guest_memory_test.c     |   6 +-
 .../kvm/memslot_modification_stress_test.c    |   6 +-
 .../testing/selftests/kvm/memslot_perf_test.c |  11 +-
 .../selftests/kvm/set_memory_region_test.c    |   8 +-
 tools/testing/selftests/kvm/steal_time.c      |   3 +-
 tools/testing/selftests/kvm/x86_64/amx_test.c |   6 +-
 .../testing/selftests/kvm/x86_64/cpuid_test.c |   2 +-
 .../kvm/x86_64/emulator_error_test.c          |   2 +-
 .../selftests/kvm/x86_64/hyperv_clock.c       |   2 +-
 .../selftests/kvm/x86_64/hyperv_features.c    |   6 +-
 .../selftests/kvm/x86_64/kvm_clock_test.c     |   2 +-
 .../selftests/kvm/x86_64/mmu_role_test.c      |   3 +-
 .../selftests/kvm/x86_64/nx_huge_pages_test.c | 149 +++++++++
 .../kvm/x86_64/nx_huge_pages_test.sh          |  25 ++
 .../selftests/kvm/x86_64/set_boot_cpu_id.c    |   2 +-
 tools/testing/selftests/kvm/x86_64/smm_test.c |   2 +-
 .../selftests/kvm/x86_64/vmx_dirty_log_test.c |  10 +-
 .../selftests/kvm/x86_64/xapic_ipi_test.c     |   2 +-
 .../selftests/kvm/x86_64/xen_shinfo_test.c    |   4 +-
 .../selftests/kvm/x86_64/xen_vmcall_test.c    |   2 +-
 48 files changed, 704 insertions(+), 190 deletions(-)
 create mode 100644 tools/testing/selftests/kvm/lib/x86_64/nx_huge_pages_guest.S
 create mode 100644 tools/testing/selftests/kvm/x86_64/nx_huge_pages_test.c
 create mode 100755 tools/testing/selftests/kvm/x86_64/nx_huge_pages_test.sh

-- 
2.35.1.616.g0bdcbb4464-goog