[RFC PATCH v2 00/34] MSR refactor with new MSR instructions support

Xin Li (Intel)
2025-04-22T08:23:51Z

Obviously the existing MSR code and the pv_ops MSR access APIs need some
love: https://lore.kernel.org/lkml/87y1h81ht4.ffs@tglx/

hpa has started a discussion about how to refactor it last October:
https://lore.kernel.org/lkml/7a4de623-ecda-4369-a7ae-0c43ef328177@zytor.com/

The consensus so far is to utilize the alternatives mechanism to eliminate
the Xen MSR access overhead on native systems and enable new MSR instructions
based on their availability.

To achieve this, a code refactor is required:

Patch 1 relocates rdtsc{,_ordered}() from <asm/msr.h> to <asm/tsc.h> and
removes the inclusion of <asm/msr.h> in <asm/tsc.h>. As a result,
<asm/msr.h> must now be explicitly included in several source files where
it was previously included implicitly through <asm/tsc.h>.

Patches 2 ~ 6 refactor the code to use the alternatives mechanism to read
PMC.

Patches 7 ~ 16 unify and simplify the MSR API definitions and usages.

Patches 17 ~ 19 add basic support for immediate form MSR instructions,
e.g., its CPU feature bit and opcode.

Patch 20 adds a new exception type to allow a function call inside an
alternative for instruction emulation to "kick back" the exception into
the alternatives pattern, possibly invoking a different exception handling
pattern there, or at least indicating the "real" location of the fault.

patches 21 and 22 refactor the code to use the alternatives mechanism to
read and write MSR.

Patches 23 ~ 34 are afterwards cleanups.

H. Peter Anvin (Intel) (1):
x86/extable: Implement EX_TYPE_FUNC_REWIND

Xin Li (Intel) (33):
x86/msr: Move rdtsc{,_ordered}() to <asm/tsc.h>
x86/msr: Remove rdpmc()
x86/msr: Rename rdpmcl() to rdpmcq()
x86/msr: Convert rdpmcq() into a function
x86/msr: Return u64 consistently in Xen PMC read functions
x86/msr: Use the alternatives mechanism to read PMC
x86/msr: Convert __wrmsr() uses to native_wrmsr{,q}() uses
x86/msr: Convert a native_wrmsr() use to native_wrmsrq()
x86/msr: Add the native_rdmsrq() helper
x86/msr: Convert __rdmsr() uses to native_rdmsrq() uses
x86/msr: Remove calling native_{read,write}_msr{,_safe}() in
pmu_msr_{read,write}()
x86/msr: Remove pmu_msr_{read,write}()
x86/xen/msr: Remove the error pointer argument from set_reg()
x86/msr: refactor pv_cpu_ops.write_msr{_safe}()
x86/msr: Replace wrmsr(msr, low, 0) with wrmsrq(msr, low)
x86/msr: Change function type of native_read_msr_safe()
x86/cpufeatures: Add a CPU feature bit for MSR immediate form
instructions
x86/opcode: Add immediate form MSR instructions
x86/extable: Add support for immediate form MSR instructions
x86/msr: Utilize the alternatives mechanism to write MSR
x86/msr: Utilize the alternatives mechanism to read MSR
x86/extable: Remove new dead code in ex_handler_msr()
x86/mce: Use native MSR API __native_{wr,rd}msrq()
x86/msr: Rename native_wrmsrq() to native_wrmsrq_no_trace()
x86/msr: Rename native_wrmsr() to native_wrmsr_no_trace()
x86/msr: Rename native_write_msr() to native_wrmsrq()
x86/msr: Rename native_write_msr_safe() to native_wrmsrq_safe()
x86/msr: Rename native_rdmsrq() to native_rdmsrq_no_trace()
x86/msr: Rename native_rdmsr() to native_rdmsr_no_trace()
x86/msr: Rename native_read_msr() to native_rdmsrq()
x86/msr: Rename native_read_msr_safe() to native_rdmsrq_safe()
x86/msr: Move the ARGS macros after the MSR read/write APIs
x86/msr: Convert native_rdmsr_no_trace() uses to
native_rdmsrq_no_trace() uses

arch/x86/boot/startup/sme.c | 5 +-
arch/x86/events/amd/brs.c | 4 +-
arch/x86/events/amd/uncore.c | 2 +-
arch/x86/events/core.c | 2 +-
arch/x86/events/intel/core.c | 4 +-
arch/x86/events/intel/ds.c | 2 +-
arch/x86/events/msr.c | 3 +
arch/x86/events/perf_event.h | 1 +
arch/x86/events/probe.c | 2 +
arch/x86/hyperv/hv_apic.c | 6 +-
arch/x86/hyperv/hv_vtl.c | 4 +-
arch/x86/hyperv/ivm.c | 7 +-
arch/x86/include/asm/apic.h | 4 +-
arch/x86/include/asm/asm.h | 6 +
arch/x86/include/asm/cpufeatures.h | 1 +
arch/x86/include/asm/extable_fixup_types.h | 1 +
arch/x86/include/asm/fred.h | 3 +-
arch/x86/include/asm/microcode.h | 10 +-
arch/x86/include/asm/mshyperv.h | 3 +-
arch/x86/include/asm/msr.h | 637 ++++++++++++------
arch/x86/include/asm/paravirt.h | 78 ---
arch/x86/include/asm/paravirt_types.h | 13 -
arch/x86/include/asm/sev-internal.h | 9 +-
arch/x86/include/asm/spec-ctrl.h | 2 +-
arch/x86/include/asm/suspend_32.h | 1 +
arch/x86/include/asm/suspend_64.h | 1 +
arch/x86/include/asm/switch_to.h | 4 +-
arch/x86/include/asm/tsc.h | 76 ++-
arch/x86/kernel/cpu/amd.c | 2 +-
arch/x86/kernel/cpu/common.c | 10 +-
arch/x86/kernel/cpu/mce/core.c | 61 +-
arch/x86/kernel/cpu/microcode/amd.c | 10 +-
arch/x86/kernel/cpu/microcode/core.c | 4 +-
arch/x86/kernel/cpu/microcode/intel.c | 8 +-
arch/x86/kernel/cpu/resctrl/pseudo_lock.c | 25 +-
arch/x86/kernel/cpu/resctrl/rdtgroup.c | 2 +-
arch/x86/kernel/cpu/scattered.c | 1 +
arch/x86/kernel/cpu/umwait.c | 4 +-
arch/x86/kernel/fpu/xstate.h | 1 +
arch/x86/kernel/hpet.c | 1 +
arch/x86/kernel/kvm.c | 2 +-
arch/x86/kernel/kvmclock.c | 2 +-
arch/x86/kernel/paravirt.c | 5 -
arch/x86/kernel/process_64.c | 1 +
arch/x86/kernel/trace_clock.c | 2 +-
arch/x86/kernel/tsc_sync.c | 1 +
arch/x86/kvm/svm/svm.c | 34 +-
arch/x86/kvm/vmx/vmx.c | 12 +-
arch/x86/lib/kaslr.c | 2 +-
arch/x86/lib/x86-opcode-map.txt | 5 +-
arch/x86/mm/extable.c | 181 +++--
arch/x86/realmode/init.c | 1 +
arch/x86/xen/enlighten_pv.c | 112 ++-
arch/x86/xen/pmu.c | 63 +-
arch/x86/xen/xen-asm.S | 113 ++++
arch/x86/xen/xen-ops.h | 14 +-
drivers/acpi/processor_perflib.c | 1 +
drivers/acpi/processor_throttling.c | 3 +-
drivers/cpufreq/amd-pstate-ut.c | 2 +
drivers/hwmon/hwmon-vid.c | 4 +
drivers/net/vmxnet3/vmxnet3_drv.c | 6 +-
.../intel/speed_select_if/isst_if_common.c | 1 +
drivers/platform/x86/intel/turbo_max_3.c | 1 +
tools/arch/x86/lib/x86-opcode-map.txt | 5 +-
64 files changed, 988 insertions(+), 605 deletions(-)

base-commit: f30a0c0d2b08b355c01392538de8fc872387cb2b
--
2.49.0