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Jim Mattson a7cec20845 KVM: x86: Provide a capability to disable APERF/MPERF read intercepts 
Allow a guest to read the physical IA32_APERF and IA32_MPERF MSRs
without interception.

The IA32_APERF and IA32_MPERF MSRs are not virtualized. Writes are not
handled at all. The MSR values are not zeroed on vCPU creation, saved
on suspend, or restored on resume. No accommodation is made for
processor migration or for sharing a logical processor with other
tasks. No adjustments are made for non-unit TSC multipliers. The MSRs
do not account for time the same way as the comparable PMU events,
whether the PMU is virtualized by the traditional emulation method or
the new mediated pass-through approach.

Nonetheless, in a properly constrained environment, this capability
can be combined with a guest CPUID table that advertises support for
CPUID.6:ECX.APERFMPERF[bit 0] to induce a Linux guest to report the
effective physical CPU frequency in /proc/cpuinfo. Moreover, there is
no performance cost for this capability.

Signed-off-by: Jim Mattson <jmattson@google.com>
Link: https://lore.kernel.org/r/20250530185239.2335185-3-jmattson@google.com
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Link: https://lore.kernel.org/r/20250626001225.744268-3-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
History 2025-07-09 09:33:37 -07:00
..
ABI Char/Misc/IIO pull request for 6.16-rc1 2025-06-06 11:50:47 -07:00
accel accel/amdxdna: Add documentation for AMD NPU accelerator driver 2024-11-22 11:40:56 -07:00
accounting Mainly individually changelogged singleton patches. The patch series in 2025-01-26 17:50:53 -08:00
admin-guide smb: client: disable path remapping with POSIX extensions 2025-06-09 15:59:03 -05:00
arch RISC-V Patches for the 6.16 Merge Window, Part 1 2025-06-06 18:05:18 -07:00
block Documentation: ublk: Separate UBLK_F_AUTO_BUF_REG fallback behavior sublists 2025-06-13 09:25:42 -06:00
bpf bpf: Add support for __prog argument suffix to pass in prog->aux 2025-05-13 18:47:54 -07:00
cdrom scsi: sr: Fix unintentional arithmetic wraparound 2024-05-15 10:05:24 -04:00
core-api Kbuild updates for v6.16 2025-06-07 10:05:35 -07:00
cpu-freq Docs/subsystem-apis: Remove '[The ]Linux' prefixes from titles of listed documents 2023-01-24 15:27:08 -07:00
crypto crypto: remove obsolete 'comp' compression API 2025-03-21 17:39:06 +08:00
dev-tools Documentation: kunit: improve example on testing static functions 2025-05-19 13:22:21 -06:00
devicetree pinctrl: MAINTAINERS: Drop bouncing Jianlong Huang 2025-06-09 10:16:46 +02:00
doc-guide Docs: doc-guide: update sphinx.rst Sphinx version number 2025-05-21 04:28:29 -06:00
driver-api Char/Misc/IIO pull request for 6.16-rc1 2025-06-06 11:50:47 -07:00
edac cxl/edac: Add CXL memory device soft PPR control feature 2025-05-23 13:25:06 -07:00
fault-injection net: Implement fault injection forcing skb reallocation 2024-11-12 12:05:33 +01:00
fb fbdev: sstfb.rst: Fix spelling mistake 2025-05-31 10:24:02 +02:00
features LoongArch: Enable ARCH_SUPPORTS_MSEAL_SYSTEM_MAPPINGS 2025-05-30 21:45:42 +08:00
filesystems docs: proc: update VmFlags documentation in smaps 2025-06-11 22:42:35 -07:00
firmware-guide Documentation: ACPI: Use all-string data node references 2025-04-09 16:39:17 +02:00
firmware_class firmware: revamp firmware documentation 2017-01-11 09:42:59 +01:00
fpga Documentation: use capitalization for chapters and acronyms 2023-05-16 12:49:31 -06:00
gpu drm fixes for 6.16-rc1 2025-06-06 08:09:56 -07:00
hid docs: hid: Fix typo in intel-thc-hid.rst 2025-04-14 10:40:52 -06:00
hwmon hwmon updates for v6.16 2025-06-03 09:11:26 -07:00
i2c docs: i2c: Fix "resitors" to "resistors" 2025-05-20 11:22:16 +02:00
iio docs: iio: ad3552r: fix malformed table 2025-05-21 14:19:46 +01:00
images docs: add SVG version of the Linux logo 2022-06-01 09:32:45 -06:00
infiniband docs: infiniband: document the UCAP API 2025-03-09 13:13:02 -04:00
input Input: amijoy - make headings compliant w/ guidelines in documentation 2025-05-30 15:34:38 -07:00
isdn Documentation: isdn: correct spelling 2023-02-10 16:28:13 -08:00
kbuild Kbuild updates for v6.16 2025-06-07 10:05:35 -07:00
kernel-hacking docs/licensing: Clarify wording about "GPL" and "Proprietary" 2024-11-22 10:44:25 -07:00
leds LEDs for v6.16 2025-06-03 12:10:31 -07:00
litmus-tests Documentation/litmus-tests: Make cmpxchg() tests safe for klitmus 2024-05-06 14:29:21 -07:00
livepatch docs: livepatch: move text out of code block 2025-03-04 16:01:29 +01:00
locking hwspinlock: Remove unused hwspin_lock_get_id() 2025-03-21 17:12:04 -05:00
maintainer docs: Remove redundant word "for" 2024-10-21 09:32:20 -06:00
mhi docs: Add documentation for MHI bus 2020-03-19 07:41:04 +01:00
misc-devices misc: amd-sbi: Add document for AMD SB IOCTL description 2025-05-21 14:44:41 +02:00
mm Docs/damon: update titles and brief introductions to explain DAMOS 2025-05-22 14:55:38 -07:00
netlabel docs: add some directories to the main documentation index 2019-07-15 11:03:03 -03:00
netlink netlink: specs: rt-link: decode ip6gre 2025-06-05 12:50:10 +02:00
networking - The 11 patch series "Add folio_mk_pte()" from Matthew Wilcox 2025-05-31 15:44:16 -07:00
nvdimm nvdimm: fixes to maintainter-entry-profile 2020-05-25 10:19:19 -06:00
nvme Documentation: typo fixes 2025-02-18 14:01:22 -07:00
PCI Merge branch 'pci/misc' 2025-06-04 10:50:45 -05:00
pcmcia Documentation: use capitalization for chapters and acronyms 2023-05-16 12:49:31 -06:00
peci Docs/subsystem-apis: Remove '[The ]Linux' prefixes from titles of listed documents 2023-01-24 15:27:08 -07:00
power PM: EM: Documentation: Fix typos in example driver code 2025-05-13 14:30:01 +02:00
process - The 3 patch series "hung_task: extend blocking task stacktrace dump to 2025-05-31 19:12:53 -07:00
RCU doc/RCU/listRCU: refine example code for eliminating stale data 2025-05-16 09:00:54 -04:00
rust Documentation: rust: testing: add docs on the new KUnit #[test] tests 2025-05-27 20:09:59 +02:00
scheduler sched_ext: Changes for v6.16 2025-05-27 21:12:50 -07:00
scsi scsi: docs: Clean up some style in scsi_mid_low_api 2025-05-12 22:11:55 -04:00
security Hi, 2025-03-28 12:42:53 -07:00
sound ASoC: doc: Add documentation for SOC USB 2025-04-11 13:02:31 +02:00
sphinx docs: kerneldoc.py: simplify exception handling logic 2025-05-21 03:53:40 -06:00
sphinx-static docs: translations: add translations links when they exist 2023-12-19 14:34:59 -07:00
spi spi: Enable controllers to extend the SPI protocol with MOSI idle configuration 2024-07-29 01:19:51 +01:00
staging rpmsg updates for v6.16 2025-06-02 11:06:44 -07:00
sunrpc/xdr nfsd: rename NFS4_SHARE_WANT_* constants to OPEN4_SHARE_ACCESS_WANT_* 2025-01-21 15:30:01 -05:00
target scsi: target: docs: Remove tcm_mod_builder.py 2023-06-28 22:01:32 -04:00
tee Documentation: tee: Add TS-TEE driver 2024-04-03 14:03:09 +02:00
timers timers/Documentation: Cleanup delay/sleep documentation 2024-10-16 00:36:48 +02:00
tools Documentation/rtla: Include BPF sample collection 2025-04-14 10:42:55 -06:00
trace Char/Misc/IIO pull request for 6.16-rc1 2025-06-06 11:50:47 -07:00
translations Kbuild updates for v6.16 2025-06-07 10:05:35 -07:00
usb USB/Thunderbolt update for 6.15-rc1 2025-04-02 18:23:31 -07:00
userspace-api LoongArch changes for v6.16 2025-06-07 09:56:18 -07:00
virt KVM: x86: Provide a capability to disable APERF/MPERF read intercepts 2025-07-09 09:33:37 -07:00
w1 w1: add UART w1 bus driver 2024-02-15 15:02:33 +01:00
watchdog watchdog: Delete the cpu5wdt driver 2024-11-05 10:04:39 +01:00
wmi platform/x86: dell-ddv: Expose the battery health to userspace 2025-05-12 13:20:42 +03:00
.gitignore .gitignore: add SPDX License Identifier 2020-03-25 11:50:48 +01:00
atomic_bitops.txt wait_on_bit: add an acquire memory barrier 2022-08-26 09:30:25 -07:00
atomic_t.txt Documentation/atomic_t: Emphasize that failed atomic operations give no ordering 2024-05-06 14:29:04 -07:00
Changes docs: add back 'Documentation/Changes' file (as symlink) 2016-12-14 16:30:12 -08:00
CodingStyle doc: re-add CodingStyle and SubmittingPatches 2016-10-24 08:12:35 -02:00
conf.py docs: conf.py: drop backward support for old Sphinx versions 2025-05-19 08:02:14 -06:00
docutils.conf doc-rst: Add missing newline at end of file 2019-06-20 14:16:56 -06:00
index.rst docs: fix typo in firmware-related section 2025-05-07 00:53:22 -06:00
Kconfig Documentation: Avoid duplicate Kconfig inclusion 2023-01-19 13:56:34 -07:00
Makefile docs: Makefile: Inherit PYTHONPYCACHEPREFIX setting as env variable 2025-05-07 00:53:22 -06:00
memory-barriers.txt docs/memory-barriers.txt: Remove left-over references to "CACHE COHERENCY" 2024-09-13 23:56:44 -07:00
SubmittingPatches doc: re-add CodingStyle and SubmittingPatches 2016-10-24 08:12:35 -02:00
subsystem-apis.rst Documentation/EDAC: Fix warning document isn't included in any toctree 2025-04-01 22:26:47 +02:00