Hi Gautam, Thanks for the update.
On 02/11/26 4:42 PM, Ritesh Harjani (IBM) wrote:
Gautam Menghani <[email protected]> writes:A huge number of spurious interrupts can be seen immediately after a KVM on PowerNV guest boots up in XIVE mode. $ cat /proc/interrupts | grep SPU SPU: 223705 192439 273526 147623 Spurious interrupts This bug was introduced by commit ecd10702baae5 ("KVM: PPC: Book3S HV: Handle pending exceptions on guest entry with MSR_EE"). The root cause is that once LPCR_MER bit is set, it is supposed to be reset by software. But when a vCPU starts running with LPCR_MER set, the vCPU does not exit back to the host until the decrementer expires or there is an hcall, etc. This is because KVM on PowerNV guests have support for native XIVE, so they are not dependent on host for interrupt emulation. Due to this behaviour, a huge number of spurious interrupts are seen since LPCR_MER continues to be set and LPCR_MER cannot be reset until the vCPU exits to the host. Fix this behaviour by not using the LPCR_MER bit whenever native XIVE is available (currently in case of KVM on PowerNV only), as the XIVE hardware can present interrupts to the KVM guest vCPU directly. So the LPCR_MER functionality is not required. This reduces the number of spurious interrupts drastically. Fixes: ecd10702baae5 ("KVM: PPC: Book3S HV: Handle pending exceptions on guest entry with MSR_EE") Cc: [email protected] # 6.8+ Reported-by: Timothy Pearson <[email protected]> Closes: https://lore.kernel.org/linuxppc-dev/582904882.11159.1786719390349.javamail.zim...@raptorengineeringinc.com Signed-off-by: Gautam Menghani <[email protected]> --- v5: 1. Drop the redundant check for the presence of the native XIVE device. (Ritesh)Thanks Gautam for confirming that. The patch looks good to me. Feel free to add: Reviewed-by: Ritesh Harjani (IBM) <[email protected]>
Using kvmppc_xive_enabled(vcpu) looks sufficient here since KVMPPC_IRQ_XIVE specifically represents XIVE native exploitation mode. It also preserves the required behaviour when switching back to XICS and when the in-kernel irqchip is not being used. The earlier case where both BOOK3S_IRQPRIO_EXTERNAL and xive_interrupt_pending() are set also remains handled by the outer condition. Reviewed-by: Narayana Murty N [email protected]
