[PATCH v2 00/66] KVM: x86: Introduce KVM cpu caps

Sean Christopherson
2020-03-02T23:57:24Z

Introduce what is effectively a KVM-specific copy of the x86_capabilities
array in boot_cpu_data, kvm_cpu_caps. kvm_cpu_caps is initialized by
copying boot_cpu_data.x86_capabilities before ->hardware_setup(). It is
then updated by KVM's CPUID logic (both common x86 and VMX/SVM specific)
to adjust the caps to reflect the CPU that KVM will expose to the guest.

Quick synopsis:
1. Refactor the KVM_GET_SUPPORTED_CPUID stack to consolidate code,
remove crustiness, and set the stage for introducing kvm_cpu_caps.

2. Introduce cpuid_entry_*() accessors/mutators to automatically
handle retrieving the correct reg from a CPUID entry, and to audit
that the entry matches the reserve CPUID lookup entry. The
cpuid_entry_*() helpers make moving the code from common x86 to
vendor code much less risky.

3. Move CPUID adjustments to vendor code in preparation for kvm_cpu_caps,
which will be initialized at load time before the kvm_x86_ops hooks
are ready to be used, i.e. before ->hardware_setup().

4. Introduce kvm_cpu_caps and move all the CPUID code over to kvm_cpu_caps.

5. Use kvm_cpu_cap_has() to kill off a bunch of ->*_supported() hooks.

6. Additional cleanup in tangentially related areas to kill off even more
->*_supported() hooks, including ->set_supported_cpuid().

Tested by verifying the output of KVM_GET_SUPPORTED_CPUID is identical
before and after on every patch on a Haswell and Coffee Lake, and for the
"before vs. after" output on Ice Lake.

Verified correctness when hiding features via Qemu (running this version
of KVM in L1), e.g. that UMIP is correctly emulated for L2 when it's
hidden from L1, on relevant patches.

Boot tested and ran kvm-unit-tests at key points, e.g. large page
handling.

All AMD patches are build-tested only.

v2:
- Opportunistically remove bare "unsigned" usgae. [Vitaly]
- Remove CPUID auditing (Vitaly and Paolo suggested making it
unconditional, then I realized it would trigger false positives).
- Fix a bug in the series that broke SVM features enumeration.
- Only advertise SVM features when nested SVM is enabled. [Paolo]
- Fully remove support for stateful CPUID.0x2. [Vitaly, Paolo]
- Call out in patch 01's changelog that it technically breaks the
ABI, but that no known VMM is affected. [Vitaly, Paolo]
- Use @function instead of hardcoding "2" for thes stateful code (which
eventually gets tossed anyways). [Vitaly]
- Move 0x8000000A into common code and kill ->set_supported_cpuid().
[Vitaly]
- Call out the subtle emulation handling in ->set_supported_cpuid(),
which also gets tossed :-). [Vitaly]
- Fix the BUILG_BUG_ON() in patch 38. [Vitaly]
- Use !! to explicitly cast a u32 to a bool. [Vitaly, Paolo]
- Sort kvm_cpu_cap_mask() calls by leaf number, ascending. [Vitaly]
- Collect reviews. [Vitaly, Vitaly, Vitaly, Vitaly, Vitaly, Vitaly,
Vitaly, Vitaly, Vitaly, Vitaly, Vitaly, Vitaly, Vitaly, Vitaly,
Vitaly, Vitaly, Vitaly, Vitaly, Vitaly, Vitaly, Vitaly, Vitaly,
Vitaly, Vitaly, Vitaly, Vitaly, Vitaly, Vitaly, Vitaly, Vitaly,
Vitaly, Vitaly, Vitaly, Vitaly, Vitaly, Vitaly, Vitaly, Vitaly,
Vitaly, Vitaly, Vitaly, Vitaly, Vitaly, Vitaly, Vitaly, Vitaly,
Vitaly, Vitaly, Vitaly, Vitaly, Vitaly, Vitaly, Vitaly, Vitaly,
Vitaly, Vitaly, Vitaly, Vitaly, Vitaly, Xiaoyao, Xiaoyao, Xiaoyao]

Sean Christopherson (66):
KVM: x86: Return -E2BIG when KVM_GET_SUPPORTED_CPUID hits max entries
KVM: x86: Refactor loop around do_cpuid_func() to separate helper
KVM: x86: Simplify handling of Centaur CPUID leafs
KVM: x86: Clean up error handling in kvm_dev_ioctl_get_cpuid()
KVM: x86: Check userapce CPUID array size after validating sub-leaf
KVM: x86: Move CPUID 0xD.1 handling out of the index>0 loop
KVM: x86: Check for CPUID 0xD.N support before validating array size
KVM: x86: Warn on zero-size save state for valid CPUID 0xD.N sub-leaf
KVM: x86: Refactor CPUID 0xD.N sub-leaf entry creation
KVM: x86: Clean up CPUID 0x7 sub-leaf loop
KVM: x86: Drop the explicit @index from do_cpuid_7_mask()
KVM: x86: Drop redundant boot cpu checks on SSBD feature bits
KVM: x86: Consolidate CPUID array max num entries checking
KVM: x86: Hoist loop counter and terminator to top of
__do_cpuid_func()
KVM: x86: Refactor CPUID 0x4 and 0x8000001d handling
KVM: x86: Encapsulate CPUID entries and metadata in struct
KVM: x86: Drop redundant array size check
KVM: x86: Use common loop iterator when handling CPUID 0xD.N
KVM: VMX: Add helpers to query Intel PT mode
KVM: x86: Calculate the supported xcr0 mask at load time
KVM: x86: Use supported_xcr0 to detect MPX support
KVM: x86: Make kvm_mpx_supported() an inline function
KVM: x86: Clear output regs for CPUID 0x14 if PT isn't exposed to
guest
KVM: x86: Drop explicit @func param from ->set_supported_cpuid()
KVM: x86: Use u32 for holding CPUID register value in helpers
KVM: x86: Replace bare "unsigned" with "unsigned int" in cpuid helpers
KVM: x86: Introduce cpuid_entry_{get,has}() accessors
KVM: x86: Introduce cpuid_entry_{change,set,clear}() mutators
KVM: x86: Refactor cpuid_mask() to auto-retrieve the register
KVM: x86: Handle MPX CPUID adjustment in VMX code
KVM: x86: Handle INVPCID CPUID adjustment in VMX code
KVM: x86: Handle UMIP emulation CPUID adjustment in VMX code
KVM: x86: Handle PKU CPUID adjustment in VMX code
KVM: x86: Handle RDTSCP CPUID adjustment in VMX code
KVM: x86: Handle Intel PT CPUID adjustment in VMX code
KVM: x86: Handle GBPAGE CPUID adjustment for EPT in VMX code
KVM: x86: Refactor handling of XSAVES CPUID adjustment
KVM: x86: Introduce kvm_cpu_caps to replace runtime CPUID masking
KVM: SVM: Convert feature updates from CPUID to KVM cpu caps
KVM: VMX: Convert feature updates from CPUID to KVM cpu caps
KVM: x86: Move XSAVES CPUID adjust to VMX's KVM cpu cap update
KVM: x86: Add a helper to check kernel support when setting cpu cap
KVM: x86: Use KVM cpu caps to mark CR4.LA57 as not-reserved
KVM: x86: Use KVM cpu caps to track UMIP emulation
KVM: x86: Fold CPUID 0x7 masking back into __do_cpuid_func()
KVM: x86: Remove the unnecessary loop on CPUID 0x7 sub-leafs
KVM: x86: Squash CPUID 0x2.0 insanity for modern CPUs
KVM: x86: Remove stateful CPUID handling
KVM: x86: Do host CPUID at load time to mask KVM cpu caps
KVM: x86: Override host CPUID results with kvm_cpu_caps
KVM: x86: Set emulated/transmuted feature bits via kvm_cpu_caps
KVM: x86: Use kvm_cpu_caps to detect Intel PT support
KVM: x86: Do kvm_cpuid_array capacity checks in terminal functions
KVM: x86: Use KVM cpu caps to detect MSR_TSC_AUX virt support
KVM: VMX: Directly use VMX capabilities helper to detect RDTSCP
support
KVM: x86: Check for Intel PT MSR virtualization using KVM cpu caps
KVM: VMX: Directly query Intel PT mode when refreshing PMUs
KVM: SVM: Refactor logging of NPT enabled/disabled
KVM: x86/mmu: Merge kvm_{enable,disable}_tdp() into a common function
KVM: x86/mmu: Configure max page level during hardware setup
KVM: x86: Don't propagate MMU lpage support to memslot.disallow_lpage
KVM: Drop largepages_enabled and its accessor/mutator
KVM: x86: Move VMX's host_efer to common x86 code
KVM: nSVM: Expose SVM features to L1 iff nested is enabled
KVM: nSVM: Advertise and enable NRIPS for L1 iff nrips is enabled
KVM: x86: Move nSVM CPUID 0x8000000A handing into common x86 code

Documentation/virt/kvm/api.rst | 22 +-
arch/x86/include/asm/kvm_host.h | 15 +-
arch/x86/kvm/cpuid.c | 874 +++++++++++++++-----------------
arch/x86/kvm/cpuid.h | 134 ++++-
arch/x86/kvm/mmu/mmu.c | 29 +-
arch/x86/kvm/svm.c | 130 ++---
arch/x86/kvm/vmx/capabilities.h | 25 +-
arch/x86/kvm/vmx/nested.c | 2 +-
arch/x86/kvm/vmx/pmu_intel.c | 2 +-
arch/x86/kvm/vmx/vmx.c | 121 +++--
arch/x86/kvm/vmx/vmx.h | 5 +-
arch/x86/kvm/x86.c | 48 +-
arch/x86/kvm/x86.h | 10 +-
include/linux/kvm_host.h | 2 -
virt/kvm/kvm_main.c | 13 -
15 files changed, 695 insertions(+), 737 deletions(-)

--
2.24.1