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Date: Fri, 16 Feb 2024 15:17:33 -0000
From: "tip-bot2 for Thomas Gleixner" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Thomas Gleixner <tglx@...utronix.de>, Juergen Gross <jgross@...e.com>,
Sohil Mehta <sohil.mehta@...el.com>, Michael Kelley <mhklinux@...look.com>,
Zhang Rui <rui.zhang@...el.com>, Wang Wendy <wendy.wang@...el.com>,
K Prateek Nayak <kprateek.nayak@....com>, x86@...nel.org,
linux-kernel@...r.kernel.org
Subject: [tip: x86/apic] x86/cpu: Provide a sane leaf 0xb/0x1f parser
The following commit has been merged into the x86/apic branch of tip:
Commit-ID: 3d41009425225ca5e09016c634ecee513b4713bb
Gitweb: https://git.kernel.org/tip/3d41009425225ca5e09016c634ecee513b4713bb
Author: Thomas Gleixner <tglx@...utronix.de>
AuthorDate: Tue, 13 Feb 2024 22:04:07 +01:00
Committer: Thomas Gleixner <tglx@...utronix.de>
CommitterDate: Thu, 15 Feb 2024 22:07:37 +01:00
x86/cpu: Provide a sane leaf 0xb/0x1f parser
detect_extended_topology() along with it's early() variant is a classic
example for duct tape engineering:
- It evaluates an array of subleafs with a boatload of local variables
for the relevant topology levels instead of using an array to save the
enumerated information and propagate it to the right level
- It has no boundary checks for subleafs
- It prevents updating the die_id with a crude workaround instead of
checking for leaf 0xb which does not provide die information.
- It's broken vs. the number of dies evaluation as it uses:
num_processors[DIE_LEVEL] / num_processors[CORE_LEVEL]
which "works" only correctly if there is none of the intermediate
topology levels (MODULE/TILE) enumerated.
There is zero value in trying to "fix" that code as the only proper fix is
to rewrite it from scratch.
Implement a sane parser with proper code documentation, which will be used
for the consolidated topology evaluation in the next step.
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Tested-by: Juergen Gross <jgross@...e.com>
Tested-by: Sohil Mehta <sohil.mehta@...el.com>
Tested-by: Michael Kelley <mhklinux@...look.com>
Tested-by: Zhang Rui <rui.zhang@...el.com>
Tested-by: Wang Wendy <wendy.wang@...el.com>
Tested-by: K Prateek Nayak <kprateek.nayak@....com>
Link: https://lore.kernel.org/r/20240212153624.830571770@linutronix.de
---
arch/x86/kernel/cpu/Makefile | 2 +-
arch/x86/kernel/cpu/topology.h | 12 +++-
arch/x86/kernel/cpu/topology_ext.c | 130 ++++++++++++++++++++++++++++-
3 files changed, 143 insertions(+), 1 deletion(-)
create mode 100644 arch/x86/kernel/cpu/topology_ext.c
diff --git a/arch/x86/kernel/cpu/Makefile b/arch/x86/kernel/cpu/Makefile
index b1c655e..45b735b 100644
--- a/arch/x86/kernel/cpu/Makefile
+++ b/arch/x86/kernel/cpu/Makefile
@@ -18,7 +18,7 @@ KMSAN_SANITIZE_common.o := n
KCSAN_SANITIZE_common.o := n
obj-y := cacheinfo.o scattered.o
-obj-y += topology_common.o topology.o
+obj-y += topology_common.o topology_ext.o topology.o
obj-y += common.o
obj-y += rdrand.o
obj-y += match.o
diff --git a/arch/x86/kernel/cpu/topology.h b/arch/x86/kernel/cpu/topology.h
index 934a100..2b100cd 100644
--- a/arch/x86/kernel/cpu/topology.h
+++ b/arch/x86/kernel/cpu/topology.h
@@ -16,6 +16,7 @@ void cpu_init_topology(struct cpuinfo_x86 *c);
void cpu_parse_topology(struct cpuinfo_x86 *c);
void topology_set_dom(struct topo_scan *tscan, enum x86_topology_domains dom,
unsigned int shift, unsigned int ncpus);
+bool cpu_parse_topology_ext(struct topo_scan *tscan);
static inline u32 topo_shift_apicid(u32 apicid, enum x86_topology_domains dom)
{
@@ -36,4 +37,15 @@ static inline u32 topo_domain_mask(enum x86_topology_domains dom)
return (1U << x86_topo_system.dom_shifts[dom]) - 1;
}
+/*
+ * Update a domain level after the fact without propagating. Used to fixup
+ * broken CPUID enumerations.
+ */
+static inline void topology_update_dom(struct topo_scan *tscan, enum x86_topology_domains dom,
+ unsigned int shift, unsigned int ncpus)
+{
+ tscan->dom_shifts[dom] = shift;
+ tscan->dom_ncpus[dom] = ncpus;
+}
+
#endif /* ARCH_X86_TOPOLOGY_H */
diff --git a/arch/x86/kernel/cpu/topology_ext.c b/arch/x86/kernel/cpu/topology_ext.c
new file mode 100644
index 0000000..e477228
--- /dev/null
+++ b/arch/x86/kernel/cpu/topology_ext.c
@@ -0,0 +1,130 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/cpu.h>
+
+#include <asm/apic.h>
+#include <asm/memtype.h>
+#include <asm/processor.h>
+
+#include "cpu.h"
+
+enum topo_types {
+ INVALID_TYPE = 0,
+ SMT_TYPE = 1,
+ CORE_TYPE = 2,
+ MAX_TYPE_0B = 3,
+ MODULE_TYPE = 3,
+ TILE_TYPE = 4,
+ DIE_TYPE = 5,
+ DIEGRP_TYPE = 6,
+ MAX_TYPE_1F = 7,
+};
+
+/*
+ * Use a lookup table for the case that there are future types > 6 which
+ * describe an intermediate domain level which does not exist today.
+ */
+static const unsigned int topo_domain_map_0b_1f[MAX_TYPE_1F] = {
+ [SMT_TYPE] = TOPO_SMT_DOMAIN,
+ [CORE_TYPE] = TOPO_CORE_DOMAIN,
+ [MODULE_TYPE] = TOPO_MODULE_DOMAIN,
+ [TILE_TYPE] = TOPO_TILE_DOMAIN,
+ [DIE_TYPE] = TOPO_DIE_DOMAIN,
+ [DIEGRP_TYPE] = TOPO_DIEGRP_DOMAIN,
+};
+
+static inline bool topo_subleaf(struct topo_scan *tscan, u32 leaf, u32 subleaf,
+ unsigned int *last_dom)
+{
+ unsigned int dom, maxtype;
+ const unsigned int *map;
+ struct {
+ // eax
+ u32 x2apic_shift : 5, // Number of bits to shift APIC ID right
+ // for the topology ID at the next level
+ : 27; // Reserved
+ // ebx
+ u32 num_processors : 16, // Number of processors at current level
+ : 16; // Reserved
+ // ecx
+ u32 level : 8, // Current topology level. Same as sub leaf number
+ type : 8, // Level type. If 0, invalid
+ : 16; // Reserved
+ // edx
+ u32 x2apic_id : 32; // X2APIC ID of the current logical processor
+ } sl;
+
+ switch (leaf) {
+ case 0x0b: maxtype = MAX_TYPE_0B; map = topo_domain_map_0b_1f; break;
+ case 0x1f: maxtype = MAX_TYPE_1F; map = topo_domain_map_0b_1f; break;
+ default: return false;
+ }
+
+ cpuid_subleaf(leaf, subleaf, &sl);
+
+ if (!sl.num_processors || sl.type == INVALID_TYPE)
+ return false;
+
+ if (sl.type >= maxtype) {
+ pr_err_once("Topology: leaf 0x%x:%d Unknown domain type %u\n",
+ leaf, subleaf, sl.type);
+ /*
+ * It really would have been too obvious to make the domain
+ * type space sparse and leave a few reserved types between
+ * the points which might change instead of following the
+ * usual "this can be fixed in software" principle.
+ */
+ dom = *last_dom + 1;
+ } else {
+ dom = map[sl.type];
+ *last_dom = dom;
+ }
+
+ if (!dom) {
+ tscan->c->topo.initial_apicid = sl.x2apic_id;
+ } else if (tscan->c->topo.initial_apicid != sl.x2apic_id) {
+ pr_warn_once(FW_BUG "CPUID leaf 0x%x subleaf %d APIC ID mismatch %x != %x\n",
+ leaf, subleaf, tscan->c->topo.initial_apicid, sl.x2apic_id);
+ }
+
+ topology_set_dom(tscan, dom, sl.x2apic_shift, sl.num_processors);
+ return true;
+}
+
+static bool parse_topology_leaf(struct topo_scan *tscan, u32 leaf)
+{
+ unsigned int last_dom;
+ u32 subleaf;
+
+ /* Read all available subleafs and populate the levels */
+ for (subleaf = 0, last_dom = 0; topo_subleaf(tscan, leaf, subleaf, &last_dom); subleaf++);
+
+ /* If subleaf 0 failed to parse, give up */
+ if (!subleaf)
+ return false;
+
+ /*
+ * There are machines in the wild which have shift 0 in the subleaf
+ * 0, but advertise 2 logical processors at that level. They are
+ * truly SMT.
+ */
+ if (!tscan->dom_shifts[TOPO_SMT_DOMAIN] && tscan->dom_ncpus[TOPO_SMT_DOMAIN] > 1) {
+ unsigned int sft = get_count_order(tscan->dom_ncpus[TOPO_SMT_DOMAIN]);
+
+ pr_warn_once(FW_BUG "CPUID leaf 0x%x subleaf 0 has shift level 0 but %u CPUs. Fixing it up.\n",
+ leaf, tscan->dom_ncpus[TOPO_SMT_DOMAIN]);
+ topology_update_dom(tscan, TOPO_SMT_DOMAIN, sft, tscan->dom_ncpus[TOPO_SMT_DOMAIN]);
+ }
+
+ set_cpu_cap(tscan->c, X86_FEATURE_XTOPOLOGY);
+ return true;
+}
+
+bool cpu_parse_topology_ext(struct topo_scan *tscan)
+{
+ /* Intel: Try leaf 0x1F first. */
+ if (tscan->c->cpuid_level >= 0x1f && parse_topology_leaf(tscan, 0x1f))
+ return true;
+
+ /* Intel/AMD: Fall back to leaf 0xB if available */
+ return tscan->c->cpuid_level >= 0x0b && parse_topology_leaf(tscan, 0x0b);
+}
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