linux/virt/kvm/arm
Marc Zyngier 8c3252c065 KVM: arm64: pmu: Reset sample period on overflow handling
The PMU emulation code uses the perf event sample period to trigger
the overflow detection. This works fine  for the *first* overflow
handling, but results in a huge number of interrupts on the host,
unrelated to the number of interrupts handled in the guest (a x20
factor is pretty common for the cycle counter). On a slow system
(such as a SW model), this can result in the guest only making
forward progress at a glacial pace.

It turns out that the clue is in the name. The sample period is
exactly that: a period. And once the an overflow has occured,
the following period should be the full width of the associated
counter, instead of whatever the guest had initially programed.

Reset the sample period to the architected value in the overflow
handler, which now results in a number of host interrupts that is
much closer to the number of interrupts in the guest.

Fixes: b02386eb7d ("arm64: KVM: Add PMU overflow interrupt routing")
Reviewed-by: Andrew Murray <andrew.murray@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
2019-10-20 10:47:07 +01:00
..
hyp KVM: arm: vgic-v3: Mark expected switch fall-through 2019-07-26 15:37:11 +01:00
vgic KVM/arm fixes for 5.4, take #1 2019-10-03 12:08:50 +02:00
aarch32.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 234 2019-06-19 17:09:07 +02:00
arch_timer.c KVM: arm64: Migrate _elx sysreg accessors to msr_s/mrs_s 2019-07-05 13:57:25 +01:00
arm.c KVM: arm/arm64: vgic: Allow more than 256 vcpus for KVM_IRQ_LINE 2019-09-09 12:29:09 +01:00
mmio.c KVM: arm/arm64: Only skip MMIO insn once 2019-08-22 13:19:56 +01:00
mmu.c arm64: switch to generic version of pte allocation 2019-07-12 11:05:45 -07:00
perf.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 234 2019-06-19 17:09:07 +02:00
pmu.c KVM: arm64: pmu: Reset sample period on overflow handling 2019-10-20 10:47:07 +01:00
psci.c KVM: arm/arm64: Add save/restore support for firmware workaround state 2019-07-05 13:56:27 +01:00
trace.h KVM: arm/arm64: Fix TRACE_INCLUDE_PATH 2019-02-19 21:05:51 +00:00