linux-kernel - [PATCH RFC 3/5] powerpc/prom: Add CPU info to hardware description string later

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Message-Id:
 <20240118-update-dump-stack-arch-str-v1-3-5c0f98d017b5@linux.ibm.com>
Date: Thu, 18 Jan 2024 09:25:14 -0600
From: Nathan Lynch via B4 Relay <devnull+nathanl.linux.ibm.com@...nel.org>
To: "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>, 
 "Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>, 
 Brian King <brking@...ux.ibm.com>, 
 Christophe Leroy <christophe.leroy@...roup.eu>, 
 John Ogness <john.ogness@...utronix.de>, 
 Michael Ellerman <mpe@...erman.id.au>, Nicholas Piggin <npiggin@...il.com>, 
 Petr Mladek <pmladek@...e.com>, 
 Sergey Senozhatsky <senozhatsky@...omium.org>, 
 Steven Rostedt <rostedt@...dmis.org>
Cc: linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org, 
 Nathan Lynch <nathanl@...ux.ibm.com>
Subject: [PATCH RFC 3/5] powerpc/prom: Add CPU info to hardware description
 string later

From: Nathan Lynch <nathanl@...ux.ibm.com>

cur_cpu_spec->cpu_name is appended to ppc_hw_desc before cur_cpu_spec
has taken on its final value. This is illustrated on pseries by
comparing the CPU name as reported at boot ("POWER8E (raw)") to the
contents of /proc/cpuinfo ("POWER8 (architected)"):

  $ dmesg | grep Hardware
  Hardware name: IBM,8408-E8E POWER8E (raw) 0x4b0201 0xf000004 \
    of:IBM,FW860.50 (SV860_146) hv:phyp pSeries

  $ grep -m 1 ^cpu /proc/cpuinfo
  cpu             : POWER8 (architected), altivec supported

Some 44x models would appear to be affected as well; see
identical_pvr_fixup().

This results in incorrect CPU information in stack dumps --
ppc_hw_desc is an input to dump_stack_set_arch_desc().

Delay gathering the CPU name until after all potential calls to
identify_cpu().

Signed-off-by: Nathan Lynch <nathanl@...ux.ibm.com>
Fixes: bd649d40e0f2 ("powerpc: Add PVR & CPU name to hardware description")
---
 arch/powerpc/kernel/prom.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
index 0b5878c3125b..c12b4434336f 100644
--- a/arch/powerpc/kernel/prom.c
+++ b/arch/powerpc/kernel/prom.c
@@ -327,6 +327,7 @@ static int __init early_init_dt_scan_cpus(unsigned long node,
 					  void *data)
 {
 	const char *type = of_get_flat_dt_prop(node, "device_type", NULL);
+	const __be32 *cpu_version = NULL;
 	const __be32 *prop;
 	const __be32 *intserv;
 	int i, nthreads;
@@ -398,7 +399,7 @@ static int __init early_init_dt_scan_cpus(unsigned long node,
 		prop = of_get_flat_dt_prop(node, "cpu-version", NULL);
 		if (prop && (be32_to_cpup(prop) & 0xff000000) == 0x0f000000) {
 			identify_cpu(0, be32_to_cpup(prop));
-			seq_buf_printf(&ppc_hw_desc, "0x%04x ", be32_to_cpup(prop));
+			cpu_version = prop;
 		}

 		check_cpu_feature_properties(node);
@@ -409,6 +410,12 @@ static int __init early_init_dt_scan_cpus(unsigned long node,
 	}

 	identical_pvr_fixup(node);
+
+	// We can now add the CPU name & PVR to the hardware description
+	seq_buf_printf(&ppc_hw_desc, "%s 0x%04lx ", cur_cpu_spec->cpu_name, mfspr(SPRN_PVR));
+	if (cpu_version)
+		seq_buf_printf(&ppc_hw_desc, "0x%04x ", be32_to_cpup(cpu_version));
+
 	init_mmu_slb_size(node);

 #ifdef CONFIG_PPC64
@@ -846,9 +853,6 @@ void __init early_init_devtree(void *params)

 	dt_cpu_ftrs_scan();

-	// We can now add the CPU name & PVR to the hardware description
-	seq_buf_printf(&ppc_hw_desc, "%s 0x%04lx ", cur_cpu_spec->cpu_name, mfspr(SPRN_PVR));
-
 	/* Retrieve CPU related informations from the flat tree
 	 * (altivec support, boot CPU ID, ...)
 	 */

-- 
2.43.0