From: Thomas Gleixner <tglx@linutronix.de>
To: Linus Torvalds <torvalds@linuxfoundation.org>
Cc: Guenter Roeck <linux@roeck-us.net>,
LKML <linux-kernel@vger.kernel.org>,
x86@kernel.org, Uros Bizjak <ubizjak@gmail.com>,
linux-sparse@vger.kernel.org, lkp@intel.com,
oe-kbuild-all@lists.linux.dev, Arnd Bergmann <arnd@kernel.org>
Subject: Re: [patch 5/9] x86: Cure per CPU madness on UP
Date: Mon, 18 Mar 2024 12:11:39 +0100 [thread overview]
Message-ID: <87zfuviyl0.ffs@tglx> (raw)
In-Reply-To: <877ci3j80k.ffs@tglx>
On Sat, Mar 16 2024 at 02:11, Thomas Gleixner wrote:
> On Fri, Mar 15 2024 at 16:23, Linus Torvalds wrote:
>> Either we should just make all machines look like they have the proper
>> local apic mappings, or we shouldn't look at any local apic rules AT
>> ALL.
>
> Sure. I can simply check if there was an APIC registered instead.
Like the below. I'm not entirely sure though whether the sanity checks
should return an error code, which is what caused the crash Guenter
observed, but I couldn't come up with something sensible either.
Returning 0 might keep the machine alive, but does it make sense?
Thanks,
tglx
---
arch/x86/kernel/cpu/topology.c | 15 +++++++++++++--
1 file changed, 13 insertions(+), 2 deletions(-)
--- a/arch/x86/kernel/cpu/topology.c
+++ b/arch/x86/kernel/cpu/topology.c
@@ -277,10 +277,21 @@ int topology_get_logical_id(u32 apicid,
/* Remove the bits below @at_level to get the proper level ID of @apicid */
unsigned int lvlid = topo_apicid(apicid, at_level);
- if (lvlid >= MAX_LOCAL_APIC)
+ if (WARN_ON_ONCE(lvlid >= MAX_LOCAL_APIC))
return -ERANGE;
- if (!test_bit(lvlid, apic_maps[at_level].map))
+
+ /*
+ * If there was no APIC registered, then the map check below would
+ * fail. With no APIC this is guaranteed to be an UP system and
+ * therefore all topology levels have only one entry and their
+ * logical ID is obviously 0.
+ */
+ if (topo_info.boot_cpu_apic_id == BAD_APICID)
+ return 0;
+
+ if (WARN_ON_ONCE(!test_bit(lvlid, apic_maps[at_level].map)))
return -ENODEV;
+
/* Get the number of set bits before @lvlid. */
return bitmap_weight(apic_maps[at_level].map, lvlid);
}
next prev parent reply other threads:[~2024-03-18 11:11 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-04 10:12 [patch 0/9] x86: Cure tons of sparse warnings (mostly __percpu) Thomas Gleixner
2024-03-04 10:12 ` [patch 1/9] perf/x86/amd/uncore: Fix __percpu annotation Thomas Gleixner
2024-03-04 10:12 ` [patch 2/9] x86/msr: Prepare for including percpu.h Thomas Gleixner
2024-03-04 10:12 ` [patch 3/9] x86/msr: Add missing __percpu annotations Thomas Gleixner
2024-03-04 10:12 ` [patch 4/9] smp: Consolidate smp_prepare_boot_cpu() Thomas Gleixner
2024-03-04 10:12 ` [patch 5/9] x86: Cure per CPU madness on UP Thomas Gleixner
2024-03-15 16:17 ` Guenter Roeck
2024-03-15 16:42 ` Linus Torvalds
2024-03-15 17:02 ` Guenter Roeck
2024-03-15 17:40 ` Thomas Gleixner
2024-03-15 22:55 ` Thomas Gleixner
2024-03-15 23:23 ` Linus Torvalds
2024-03-16 1:11 ` Thomas Gleixner
2024-03-16 1:23 ` Linus Torvalds
2024-03-16 21:34 ` Arnd Bergmann
2024-03-17 21:03 ` David Laight
2024-03-18 11:11 ` Thomas Gleixner [this message]
2024-03-18 17:27 ` Thomas Gleixner
2024-03-18 19:13 ` Arnd Bergmann
2024-03-19 16:21 ` Thomas Gleixner
2024-03-19 18:26 ` Guenter Roeck
2024-03-16 0:56 ` Guenter Roeck
2024-03-20 8:58 ` Thomas Gleixner
2024-03-20 15:46 ` Guenter Roeck
2024-03-21 11:14 ` Thomas Gleixner
2024-03-21 14:06 ` Guenter Roeck
2024-03-21 16:49 ` Thomas Gleixner
2024-03-04 10:12 ` [patch 6/9] x86/uaccess: Add missing __force to casts in __access_ok() and valid_user_address() Thomas Gleixner
2024-03-04 10:12 ` [patch 7/9] x86/cpu: Use EXPORT_PER_CPU_SYMBOL_GPL() for x86_spec_ctrl_current Thomas Gleixner
2024-03-04 10:12 ` [patch 8/9] x86/cpu: Provide a declaration for itlb_multihit_kvm_mitigation Thomas Gleixner
2024-03-04 10:12 ` [patch 9/9] x86/callthunks: Use EXPORT_PER_CPU_SYMBOL_GPL() for per CPU variables Thomas Gleixner
2024-03-04 11:08 ` [patch 0/9] x86: Cure tons of sparse warnings (mostly __percpu) Ingo Molnar
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