On behalf of Xin, to avoid having to resolve conflicts when applying. This applies on the fastpath cleanup series: https://lore.kernel.org/all/20250805190526.1453366-1-seanjc@xxxxxxxxxx This patch set handles two newly introduced VM exit reasons associated with the immediate form of MSR instructions to ensure proper virtualization of these instructions. The immediate form of MSR access instructions are primarily motivated by performance, not code size: by having the MSR number in an immediate, it is available *much* earlier in the pipeline, which allows the hardware much more leeway about how a particular MSR is handled. For proper virtualization of the immediate form of MSR instructions, Intel VMX architecture adds the following changes: 1) The immediate form of RDMSR uses VM exit reason 84. 2) The immediate form of WRMSRNS uses VM exit reason 85. 3) For both VM exit reasons 84 and 85, the exit qualification is set to the MSR address causing the VM exit. 4) Bits 3 ~ 6 of the VM exit instruction information field represent the operand register used in the immediate form of MSR instruction. 5) The VM-exit instruction length field records the size of the immediate form of the MSR instruction. Note: The VMX specification for the immediate form of MSR instructions was inadvertently omitted from the last published ISE, but it will be included in the upcoming edition. Linux bare metal support of the immediate form of MSR instructions is still under development; however, the KVM support effort is proceeding independently of the bare metal implementation. v3: - Rebase on the fastpath cleanups. - Split patches to better isolate the functional changes. - Massage and expand on a changelogs. - Make a handful of (mostly) stylistic changes (shouldn't affect functionality, key word "should"). v2: https://lore.kernel.org/all/20250802001520.3142577-1-xin@xxxxxxxxx v1: https://lore.kernel.org/lkml/20250730174605.1614792-1-xin@xxxxxxxxx Sean Christopherson (1): KVM: x86: Rename local "ecx" variables to "msr" and "pmc" as appropriate Xin Li (5): x86/cpufeatures: Add a CPU feature bit for MSR immediate form instructions KVM: x86: Rename handle_fastpath_set_msr_irqoff() to handle_fastpath_wrmsr() KVM: x86: Add support for RDMSR/WRMSRNS w/ immediate on Intel KVM: VMX: Support the immediate form of WRMSRNS in the VM-Exit fastpath KVM: x86: Advertise support for the immediate form of MSR instructions arch/x86/include/asm/cpufeatures.h | 1 + arch/x86/include/asm/kvm_host.h | 4 ++ arch/x86/include/uapi/asm/vmx.h | 6 +- arch/x86/kernel/cpu/scattered.c | 1 + arch/x86/kvm/cpuid.c | 6 +- arch/x86/kvm/reverse_cpuid.h | 5 ++ arch/x86/kvm/svm/svm.c | 8 ++- arch/x86/kvm/vmx/nested.c | 13 ++++- arch/x86/kvm/vmx/vmx.c | 26 ++++++++- arch/x86/kvm/vmx/vmx.h | 5 ++ arch/x86/kvm/x86.c | 94 ++++++++++++++++++++++-------- arch/x86/kvm/x86.h | 3 +- 12 files changed, 139 insertions(+), 33 deletions(-) base-commit: 53d61a43a7973f812caa08fa922b607574befef4 -- 2.50.1.565.gc32cd1483b-goog
