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64074ca8ca
Reload the perf event when setting the vPMU counter (vPMC) registers (PMCCNTR_EL0 and PMEVCNTR<n>_EL0). This is a change corresponding to commit9228b26194("KVM: arm64: PMU: Fix GET_ONE_REG for vPMC regs to return the current value") but for SET_ONE_REG. Values of vPMC registers are saved in sysreg files on certain occasions. These saved values don't represent the current values of the vPMC registers if the perf events for the vPMCs count events after the save. The current values of those registers are the sum of the sysreg file value and the current perf event counter value. But, when userspace writes those registers (using KVM_SET_ONE_REG), KVM only updates the sysreg file value and leaves the current perf event counter value as is. It is also important to keep the correct state even if userspace writes them after first run, specifically when debugging Windows on QEMU with GDB; QEMU tries to write back all visible registers when resuming the VM execution with GDB, corrupting the PMU state. Windows always uses the PMU so this can cause adverse effects on that particular OS. Fix this by releasing the current perf event and trigger recreating one with KVM_REQ_RELOAD_PMU. Fixes:051ff581ce("arm64: KVM: Add access handler for event counter register") Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com> Reviewed-by: Marc Zyngier <maz@kernel.org> Link: https://lore.kernel.org/r/20250315-pmc-v5-3-ecee87dab216@daynix.com Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.