x86, AMD: Make cpu_has_amd_erratum() use the correct struct cpuinfo_x86

PATCH In review Torsten Kaiser 2 participants 2 messages Jul 23, 2013 – Aug 7, 2013 x86

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Torsten Kaiser

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2013-07-23 17:40 UTC #0 lore raw

PATCH v2 1/1 x86, AMD: Make cpu_has_amd_erratum() use the correct struct cpuinfo_x86

cpu_has_amd_erratum() is buggy, because it uses the per-cpu cpu_info before it is filled by smp_store_boot_cpu_info() / smp_store_cpu_info().

If early microcode loading is enabled its collect_cpu_info_amd_early() will fill ->x86 and so the fallback to boot_cpu_data is not used.
But ->x86_vendor was not filled and is still 0 == X86_VENDOR_INTEL resulting in no errata fixes getting applied and my system hangs on boot.

Using cpu_info in cpu_has_amd_erratum() is wrong anyway: Its only caller init_amd() will have a struct cpuinfo_x86 as parameter and the set_cpu_bug() that is controlled by cpu_has_amd_erratum() also only uses that struct.

So pass the struct cpuinfo_x86 from init_amd() to cpu_has_amd_erratum() and the broken fallback can be dropped.

I also added an WARN_ON() into the vendor check because init_amd() can only be used by AMD CPUs and if the current failure hadn't been silent this bug would have been much more obvious.

V2: At request of Borislav Petkov: BUG_ON -> WARN_ON and subject change

Signed-off-by Torsten Kaiser <[email protected]>

arch/x86/kernel/cpu/amd.c +8 ~~-14~~

@@ -512,7 +512,7 @@ static void early_init_amd(struct cpuinf
 
 static const int amd_erratum_383[];
 static const int amd_erratum_400[];
-static bool cpu_has_amd_erratum(const int *erratum);
+static bool cpu_has_amd_erratum(struct cpuinfo_x86 *cpu, const int *erratum);
 
 static void init_amd(struct cpuinfo_x86 *c)
 {

@@ -729,11 +729,11 @@ static void init_amd(struct cpuinfo_x86
 		value &= ~(1ULL << 24);
 		wrmsrl_safe(MSR_AMD64_BU_CFG2, value);
 
-		if (cpu_has_amd_erratum(amd_erratum_383))
+		if (cpu_has_amd_erratum(c, amd_erratum_383))
 			set_cpu_bug(c, X86_BUG_AMD_TLB_MMATCH);
 	}
 
-	if (cpu_has_amd_erratum(amd_erratum_400))
+	if (cpu_has_amd_erratum(c, amd_erratum_400))
 		set_cpu_bug(c, X86_BUG_AMD_APIC_C1E);
 
 	rdmsr_safe(MSR_AMD64_PATCH_LEVEL, &c->microcode, &dummy);

@@ -878,22 +878,16 @@ static const int amd_erratum_400[] =
 static const int amd_erratum_383[] =
 	AMD_OSVW_ERRATUM(3, AMD_MODEL_RANGE(0x10, 0, 0, 0xff, 0xf));
 
-static bool cpu_has_amd_erratum(const int *erratum)
+
+static bool cpu_has_amd_erratum(struct cpuinfo_x86 *cpu, const int *erratum)
 {
-	struct cpuinfo_x86 *cpu = __this_cpu_ptr(&cpu_info);
 	int osvw_id = *erratum++;
 	u32 range;
 	u32 ms;
 
-	/*
-	 * If called early enough that current_cpu_data hasn't been initialized
-	 * yet, fall back to boot_cpu_data.
-	 */
-	if (cpu->x86 == 0)
-		cpu = &boot_cpu_data;
-
-	if (cpu->x86_vendor != X86_VENDOR_AMD)
-		return false;
+	/* Should never be called on non-AMD-CPUs */
+	if (WARN_ON(cpu->x86_vendor != X86_VENDOR_AMD))
+		return false;
 
 	if (osvw_id >= 0 && osvw_id < 65536 &&
 	    cpu_has(cpu, X86_FEATURE_OSVW)) {

Borislav Petkov

maintainer Acked-by on v2 1/1

2013-08-07 06:51 UTC #1 lore raw

Quoted 15 lines · Torsten Kaiser

cpu_has_amd_erratum() is buggy, because it uses the per-cpu cpu_info before it is filled by smp_store_boot_cpu_info() / smp_store_cpu_info().
If early microcode loading is enabled its collect_cpu_info_amd_early() will fill ->x86 and so the fallback to boot_cpu_data is not used.
But ->x86_vendor was not filled and is still 0 == X86_VENDOR_INTEL resulting in no errata fixes getting applied and my system hangs on boot.
Using cpu_info in cpu_has_amd_erratum() is wrong anyway: Its only caller init_amd() will have a struct cpuinfo_x86 as parameter and the set_cpu_bug() that is controlled by cpu_has_amd_erratum() also only uses that struct.
So pass the struct cpuinfo_x86 from init_amd() to cpu_has_amd_erratum() and the broken fallback can be dropped.

Quoted 7 lines

I also added an WARN_ON() into the vendor check because init_amd() can only be used by AMD CPUs and if the current failure hadn't been silent this bug would have been much more obvious.
V2: At request of Borislav Petkov: BUG_ON -> WARN_ON and subject change
Signed-off-by Torsten Kaiser <[email protected]>

Acked-by Borislav Petkov <[email protected]>

Signature · 5 lines

Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
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