Re: [REGRESSION] mainline boot regression on AMD Stoney Ridge Chromebooks

Thomas Gleixner
2024-04-04T18:06:52Z

Laura!

On Thu, Apr 04 2024 at 18:14, Thomas Gleixner wrote:
> Can you please provide 'cpuid -r' output too as 'cpuid' does a few
> tweaks to the raw data and it's hard to match it back to the code.

Don't bother. I think I figured it out.

Can you please test the patch below?

Thanks,

tglx
---
diff --git a/arch/x86/kernel/cpu/topology_amd.c b/arch/x86/kernel/cpu/topology_amd.c
index 1a8b3ad493af..0d91a04b1741 100644
--- a/arch/x86/kernel/cpu/topology_amd.c
+++ b/arch/x86/kernel/cpu/topology_amd.c
@@ -29,7 +29,17 @@ static bool parse_8000_0008(struct topo_scan *tscan)
if (!sft)
sft = get_count_order(ecx.cpu_nthreads + 1);

- topology_set_dom(tscan, TOPO_SMT_DOMAIN, sft, ecx.cpu_nthreads + 1);
+ /*
+ * cpu_nthreads describes the number of threads in the package
+ * sft is the number of APIC ID bits per package
+ *
+ * As the number of actual threads per core is not described in
+ * this leaf, just set the CORE domain shift and let the later
+ * parsers set SMT shift. Assume one thread per core by default
+ * which is correct if there are no other CPUID leafs to parse.
+ */
+ topology_update_dom(tscan, TOPO_SMT_DOMAIN, 0, 1);
+ topology_set_dom(tscan, TOPO_CORE_DOMAIN, sft, ecx.cpu_nthreads + 1);
return true;
}

@@ -73,12 +83,14 @@ static bool parse_8000_001e(struct topo_scan *tscan, bool has_0xb)
tscan->c->topo.initial_apicid = leaf.ext_apic_id;

/*
- * If leaf 0xb is available, then SMT shift is set already. If not
- * take it from ecx.threads_per_core and use topo_update_dom() -
- * topology_set_dom() would propagate and overwrite the already
- * propagated CORE level.
+ * If leaf 0xb is available, then the domain shifts are set
+ * already and nothing to do here.
*/
if (!has_0xb) {
+ /*
+ * Leaf 0x80000008 set the CORE domain shift already.
+ * Update the SMT domain, but do not propagate it.
+ */
unsigned int nthreads = leaf.core_nthreads + 1;

topology_update_dom(tscan, TOPO_SMT_DOMAIN, get_count_order(nthreads), nthreads);