linux-kernel - Re: [PATCH 3/3] x86/mce: Use mce_prep_record() helpers for apei_smca_report_x86

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Message-ID: <20240603165530.GFZl31gtuABwpe1svP@fat_crate.local>
Date: Mon, 3 Jun 2024 18:55:30 +0200
From: Borislav Petkov <bp@...en8.de>
To: Yazen Ghannam <yazen.ghannam@....com>
Cc: linux-edac@...r.kernel.org, linux-kernel@...r.kernel.org,
	tony.luck@...el.com, x86@...nel.org, avadhut.naik@....com,
	john.allen@....com
Subject: Re: [PATCH 3/3] x86/mce: Use mce_prep_record() helpers for
 apei_smca_report_x86_error()

On Mon, Jun 03, 2024 at 10:34:10AM -0400, Yazen Ghannam wrote:
> One day I'll break this habit. Thanks again for the reminder. :)

Sure, np. :-)

> >>  	for_each_possible_cpu(cpu) {
> >> -		if (cpu_data(cpu).topo.initial_apicid == lapic_id) {
> >> -			m.extcpu = cpu;
> >> -			m.socketid = cpu_data(m.extcpu).topo.pkg_id;
> >> +		if (cpu_data(cpu).topo.initial_apicid == lapic_id)
> >>  			break;
> >> -		}
> >>  	}
> >>  
> >> -	m.apicid = lapic_id;
> >> +	if (!cpu_possible(cpu))
> >> +		return -EINVAL;
> > 
> > What's that test for? You just iterated over the possible CPUs using
> > "cpu" as the iterator there...
> > 
> 
> This is to catch the case where there was no break from the loop.

If the CPU is possible != whether there was a apicid match.

Here's how you do that and I'd let you figure out why yours doesn't
always work:

diff --git a/arch/x86/kernel/cpu/mce/apei.c b/arch/x86/kernel/cpu/mce/apei.c
index 0cbadfaf2400..3885fe05f01e 100644
--- a/arch/x86/kernel/cpu/mce/apei.c
+++ b/arch/x86/kernel/cpu/mce/apei.c
@@ -66,6 +66,7 @@ EXPORT_SYMBOL_GPL(apei_mce_report_mem_error);
 int apei_smca_report_x86_error(struct cper_ia_proc_ctx *ctx_info, u64 lapic_id)
 {
 	const u64 *i_mce = ((const u64 *) (ctx_info + 1));
+	bool apicid_found = false;
 	unsigned int cpu;
 	struct mce m;
 
@@ -98,11 +99,13 @@ int apei_smca_report_x86_error(struct cper_ia_proc_ctx *ctx_info, u64 lapic_id)
 		return -EINVAL;
 
 	for_each_possible_cpu(cpu) {
-		if (cpu_data(cpu).topo.initial_apicid == lapic_id)
+		if (cpu_data(cpu).topo.initial_apicid == lapic_id) {
+			apicid_found = true;
 			break;
+		}
 	}
 
-	if (!cpu_possible(cpu))
+	if (!apicid_found)
 		return -EINVAL;
 
 	mce_prep_record_common(&m);


Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette