Looks good.
Reviewed-by: Caleb Schlossin <cal...@linux.ibm.com>
On 5/11/25 10:10 PM, Nicholas Piggin wrote:
> From: Glenn Miles <mil...@linux.ibm.com>
>
> A problem was seen where uart interrupts would be lost resulting in the
> console hanging. Traces showed that a lower priority interrupt was
> preempting a higher priority interrupt, which would result in the higher
> priority interrupt never being handled.
>
> The new interrupt's priority was being compared against the CPPR
> (Current Processor Priority Register) instead of the PIPR (Post
> Interrupt Priority Register), as was required by the XIVE spec.
> This allowed for a window between raising an interrupt and ACK'ing
> the interrupt where a lower priority interrupt could slip in.
>
> Fixes: 26c55b99418 ("ppc/xive2: Process group backlog when updating the CPPR")
> Signed-off-by: Glenn Miles <mil...@linux.ibm.com>
> ---
> hw/intc/xive2.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/hw/intc/xive2.c b/hw/intc/xive2.c
> index 453fe37f18..2b4d0f51be 100644
> --- a/hw/intc/xive2.c
> +++ b/hw/intc/xive2.c
> @@ -1283,7 +1283,7 @@ bool xive2_tm_irq_precluded(XiveTCTX *tctx, int ring,
> uint8_t priority)
> * priority to know if the thread can take the interrupt now or if
> * it is precluded.
> */
> - if (priority < alt_regs[TM_CPPR]) {
> + if (priority < alt_regs[TM_PIPR]) {
> return false;
> }
> return true;
