On 6 August 2014 19:54, Will Deacon <will.deacon@xxxxxxx> wrote: > On Tue, Aug 05, 2014 at 10:24:11AM +0100, Anup Patel wrote: >> A hypervisor will typically mask the overflow interrupt before >> forwarding it to Guest Linux hence we need to re-enable the overflow >> interrupt after clearing it in Guest Linux. Also, this re-enabling >> of overflow interrupt does not harm in non-virtualized scenarios. >> >> Signed-off-by: Pranavkumar Sawargaonkar <pranavkumar@xxxxxxxxxx> >> Signed-off-by: Anup Patel <anup.patel@xxxxxxxxxx> >> --- >> arch/arm64/kernel/perf_event.c | 8 ++++++++ >> 1 file changed, 8 insertions(+) >> >> diff --git a/arch/arm64/kernel/perf_event.c b/arch/arm64/kernel/perf_event.c >> index 47dfb8b..19fb140 100644 >> --- a/arch/arm64/kernel/perf_event.c >> +++ b/arch/arm64/kernel/perf_event.c >> @@ -1076,6 +1076,14 @@ static irqreturn_t armv8pmu_handle_irq(int irq_num, void *dev) >> if (!armv8pmu_counter_has_overflowed(pmovsr, idx)) >> continue; >> >> + /* >> + * If we are running under a hypervisor such as KVM then >> + * hypervisor will mask the interrupt before forwarding >> + * it to Guest Linux hence re-enable interrupt for the >> + * overflowed counter. >> + */ >> + armv8pmu_enable_intens(idx); >> + > > Really? This is a giant bodge in the guest to work around short-comings in > the hypervisor. Why can't we fix this properly using something like Marc's > irq forwarding code? This change is in accordance with our previous RFC thread about PMU virtualization where Marc Z had suggest to do interrupt mask/unmask dance similar to arch-timer. I have not tried Marc'z irq forwarding series. In next revision of this patchset, I will try to use Marc's irq forwarding approach. > > Will -- Anup -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
