[BUG] Interrupt timing warnings in pSeries guest on PowerNV host

[BUG] Interrupt timing warnings in pSeries guest on PowerNV host

[Timothy Pearson]

On a POWER9/PowerNV host, when running a pSeries guest using QEMU, sporadic interrupt timing warnings are observed.  This is on kernel 6.12 (Debian Stable) on both host and guest, system load is moderate, the host CPUs are not pegged at 100% at any time.  The guest has only one virtual CPU core assigned.

[11622.031047] hrtimer: interrupt took 12354614 ns
[46723.139964] hrtimer: interrupt took 8522695 ns

This *may* be related to the dropped / late interrupts I have reported in earlier messages, but it could also be a separate issue.  QEMU version is 7.2.22.

Re: [BUG] Interrupt timing warnings in pSeries guest on PowerNV host

[Shrikanth Hegde]

Hi Timothy,

On 8/21/26 10:08 PM, Timothy Pearson wrote:
> On a POWER9/PowerNV host, when running a pSeries guest using QEMU, sporadic interrupt timing warnings are observed.  This is on kernel 6.12 (Debian Stable) on both host and guest, system load is moderate, the host CPUs are not pegged at 100% at any time.  The guest has only one virtual CPU core assigned.
> 
> [11622.031047] hrtimer: interrupt took 12354614 ns
> [46723.139964] hrtimer: interrupt took 8522695 ns
> 

         /*
          * The next timer was already expired due to:
          * - tracing
          * - long lasting callbacks
          * - being scheduled away when running in a VM

This message used to come if the timer expiry was in past and it was tried 3 times and still
can't catch up.  Very likely it was due to guest being scheduled away.

This behavior has changed now and this particular trace has been removed.
https://lore.kernel.org/all/20260224163430.870639266@kernel.org/

> This *may* be related to the dropped / late interrupts I have reported in earlier messages, but it could also be a separate issue.  QEMU version is 7.2.22.