diff mbox series

[V2,4/8] x86/topology: Fix multiple packages shown on a single-package system

Message ID 20220816051633.17775-5-rui.zhang@intel.com (mailing list archive)
State Handled Elsewhere
Headers show
Series x86/topology: Improve CPUID.1F handling | expand

Commit Message

Zhang Rui Aug. 16, 2022, 5:16 a.m. UTC 
CPUID.1F/B does not emumerate Package level explicitly, instead, all the
APIC-ID bits above the enumerated levels are assumed to be package ID
bits.

Current code gets package ID by shifting out all the APIC-ID bits that
Linux supports, rather than shifting out all the APIC-ID bits that
CPUID.1F enumerates. This introduces problems when CPUID.1F enumerates a
level that Linux does not support.

For example, on an AlderLake-N platform, there are 2 Ecore Modules, which
has 4 atom cores in each module, in a single package.
Linux does not support Module level and interprets the Module ID bits as
package ID and erroneously reports a multi module system as a
multi-package system.

Fix this by using APIC-ID bits above all the CPUID.1F enumerated levels as
package ID.

Suggested-and-reviewed-by: Len Brown <len.brown@intel.com>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>
---
 arch/x86/kernel/cpu/topology.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

Comments

Dave Hansen Sept. 21, 2022, 4:26 p.m. UTC | #1 
On 8/15/22 22:16, Zhang Rui wrote:
> Suggested-and-reviewed-by: Len Brown <len.brown@intel.com>
> Signed-off-by: Zhang Rui <rui.zhang@intel.com>

"Please do not use combined tags, e.g. Reported-and-tested-by, as they
just complicate automated extraction of tags."

https://www.kernel.org/doc/html/latest/process/maintainer-tip.html
Zhang Rui Sept. 22, 2022, 1:38 p.m. UTC | #2 
Hi, Dave,

On Wed, 2022-09-21 at 09:26 -0700, Dave Hansen wrote:
> On 8/15/22 22:16, Zhang Rui wrote:
> > Suggested-and-reviewed-by: Len Brown <len.brown@intel.com>
> > Signed-off-by: Zhang Rui <rui.zhang@intel.com>
> 
> "Please do not use combined tags, e.g. Reported-and-tested-by, as
> they
> just complicate automated extraction of tags."
> 
> https://www.kernel.org/doc/html/latest/process/maintainer-tip.html

Thanks for pointing this out.
Problem is addressed in V3 series.

thanks,
rui
diff mbox series

Patch

diff --git a/arch/x86/kernel/cpu/topology.c b/arch/x86/kernel/cpu/topology.c
index 132a2de44d2f..f7592814e5d5 100644
--- a/arch/x86/kernel/cpu/topology.c
+++ b/arch/x86/kernel/cpu/topology.c
@@ -96,6 +96,7 @@  int detect_extended_topology(struct cpuinfo_x86 *c)
 	unsigned int ht_mask_width, core_plus_mask_width, die_plus_mask_width;
 	unsigned int core_select_mask, core_level_siblings;
 	unsigned int die_select_mask, die_level_siblings;
+	unsigned int pkg_mask_width;
 	bool die_level_present = false;
 	int leaf;
 
@@ -111,10 +112,10 @@  int detect_extended_topology(struct cpuinfo_x86 *c)
 	core_level_siblings = smp_num_siblings = LEVEL_MAX_SIBLINGS(ebx);
 	core_plus_mask_width = ht_mask_width = BITS_SHIFT_NEXT_LEVEL(eax);
 	die_level_siblings = LEVEL_MAX_SIBLINGS(ebx);
-	die_plus_mask_width = BITS_SHIFT_NEXT_LEVEL(eax);
+	pkg_mask_width = die_plus_mask_width = BITS_SHIFT_NEXT_LEVEL(eax);
 
 	sub_index = 1;
-	do {
+	while (true) {
 		cpuid_count(leaf, sub_index, &eax, &ebx, &ecx, &edx);
 
 		/*
@@ -132,8 +133,13 @@  int detect_extended_topology(struct cpuinfo_x86 *c)
 			die_plus_mask_width = BITS_SHIFT_NEXT_LEVEL(eax);
 		}
 
+		if (LEAFB_SUBTYPE(ecx) != INVALID_TYPE)
+			pkg_mask_width = BITS_SHIFT_NEXT_LEVEL(eax);
+		else
+			break;
+
 		sub_index++;
-	} while (LEAFB_SUBTYPE(ecx) != INVALID_TYPE);
+	}
 
 	core_select_mask = (~(-1 << core_plus_mask_width)) >> ht_mask_width;
 	die_select_mask = (~(-1 << die_plus_mask_width)) >>
@@ -148,7 +154,7 @@  int detect_extended_topology(struct cpuinfo_x86 *c)
 	}
 
 	c->phys_proc_id = apic->phys_pkg_id(c->initial_apicid,
-				die_plus_mask_width);
+				pkg_mask_width);
 	/*
 	 * Reinit the apicid, now that we have extended initial_apicid.
 	 */