Re: [PATCH v2 1/8] powerpc/xive: Use cpu_to_node() instead of ibm,chip-id property
From: Greg Kurz <hidden>
Date: 2021-03-08 17:24:01
On Wed, 3 Mar 2021 18:48:50 +0100 Cédric Le Goater [off-list ref] wrote:
The 'chip_id' field of the XIVE CPU structure is used to choose a target for a source located on the same chip when possible. This field is assigned on the PowerNV platform using the "ibm,chip-id" property on pSeries under KVM when NUMA nodes are defined but it is undefined
This sentence seems to have a syntax problem... like it is missing an 'and' before 'on pSeries'.
under PowerVM. The XIVE source structure has a similar field 'src_chip' which is only assigned on the PowerNV platform. cpu_to_node() returns a compatible value on all platforms, 0 being the default node. It will also give us the opportunity to set the affinity of a source on pSeries when we can localize them.
IIUC this relies on the fact that the NUMA node id is == to chip id on PowerNV, i.e. xc->chip_id which is passed to OPAL remain stable with this change. On the other hand, you have the pSeries case under PowerVM that doesn't xc->chip_id, which isn't passed to any hcall AFAICT. It looks like the chip id is only used for localization purpose in this case, right ? In this case, what about doing this change for pSeries only, somewhere in spapr.c ?
quoted hunk ↗ jump to hunk
Signed-off-by: Cédric Le Goater <clg@kaod.org> --- arch/powerpc/sysdev/xive/common.c | 7 +------ 1 file changed, 1 insertion(+), 6 deletions(-)diff --git a/arch/powerpc/sysdev/xive/common.c b/arch/powerpc/sysdev/xive/common.c index 595310e056f4..b8e456da28aa 100644 --- a/arch/powerpc/sysdev/xive/common.c +++ b/arch/powerpc/sysdev/xive/common.c@@ -1335,16 +1335,11 @@ static int xive_prepare_cpu(unsigned int cpu) xc = per_cpu(xive_cpu, cpu); if (!xc) { - struct device_node *np; - xc = kzalloc_node(sizeof(struct xive_cpu), GFP_KERNEL, cpu_to_node(cpu)); if (!xc) return -ENOMEM; - np = of_get_cpu_node(cpu, NULL); - if (np) - xc->chip_id = of_get_ibm_chip_id(np); - of_node_put(np); + xc->chip_id = cpu_to_node(cpu); xc->hw_ipi = XIVE_BAD_IRQ; per_cpu(xive_cpu, cpu) = xc;