linux-kernel - Re: [PATCH] x86/AMD: Apply erratum 688 on machines without a BIOS fix

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Date:   Sat, 22 Oct 2016 16:12:29 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     sonofagun@...nmailbox.org
Cc:     linux-kernel@...r.kernel.org, Nikos Barkas <levelwol@...il.com>
Subject: Re: [PATCH] x86/AMD: Apply erratum 688 on machines without a BIOS fix

On Sat, Oct 22, 2016 at 02:16:41PM +0300, sonofagun@...nmailbox.org wrote:
> Patch does not compile.

Yeah, it needs more work.

Try the version below. It needs to be done differently because we need
PCI extended config space access to be enabled in order to check bit 2.

> To be honest I can't say. My brother's machine(s) has random crashes from
> time to time. We suspect that this erratum is to blame. He must have kept
> some information at least from one of those crashes but there was no time to
> analyze them till now. Finding those logs on our disks needs a big effort
> but it will be done! We are willing to discover the trouble maker no matter
> what it takes. To do that the machine must be stripped off from all cards
> and then put on quarantine. Then we can connect it with a another machine
> with an RS-232 cable to see what is wrong. After that we must test it on a
> different motherboard we have. I think we have one with a BIOS from a
> different BIOS vendor. We will surely inform you on this one as we can't do
> such a patch. So we will focus on triggering this bug. One thing is sure,
> its BIOS has no workaround for that erratum.

Ok, good. Let me know how it goes.

Thanks.

---
>From ddce976ba7fc44922a6c4e9e58bbdf65c65c4ae4 Mon Sep 17 00:00:00 2001
From: Borislav Petkov <bp@...e.de>
Date: Sat, 22 Oct 2016 15:23:54 +0200
Subject: [PATCH] E688, v1

Signed-off-by: Borislav Petkov <bp@...e.de>
---
diff --git a/arch/x86/kernel/amd_nb.c b/arch/x86/kernel/amd_nb.c
index 4fdf6230d93c..bfde06b1a587 100644
--- a/arch/x86/kernel/amd_nb.c
+++ b/arch/x86/kernel/amd_nb.c
@@ -15,6 +15,8 @@
 
 static u32 *flush_words;
 
+#define PCI_DEVICE_ID_AMD_CNB17H_F4     0x1704
+
 const struct pci_device_id amd_nb_misc_ids[] = {
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_K8_NB_MISC) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_10H_NB_MISC) },
@@ -24,6 +26,7 @@ const struct pci_device_id amd_nb_misc_ids[] = {
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_15H_M60H_NB_F3) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_16H_NB_F3) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_16H_M30H_NB_F3) },
+	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_CNB17H_F3) },
 	{}
 };
 EXPORT_SYMBOL(amd_nb_misc_ids);
@@ -34,6 +37,7 @@ static const struct pci_device_id amd_nb_link_ids[] = {
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_15H_M60H_NB_F4) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_16H_NB_F4) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_16H_M30H_NB_F4) },
+	{ PCI_DEVICE(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_CNB17H_F4) },
 	{}
 };
 
@@ -274,11 +278,46 @@ void amd_flush_garts(void)
 }
 EXPORT_SYMBOL_GPL(amd_flush_garts);
 
+static void __fix_erratum_688(void *info)
+{
+#define MSR_AMD64_IC_CFG 0xC0011021
+
+	msr_set_bit(MSR_AMD64_IC_CFG, 3);
+	msr_set_bit(MSR_AMD64_IC_CFG, 14);
+}
+
+/* Apply erratum 688 fix so machines without a BIOS fix work. */
+static __init void fix_erratum_688(void)
+{
+	struct pci_dev *F4;
+	u32 val;
+
+	if (boot_cpu_data.x86 != 0x14)
+		return;
+
+	if (!amd_northbridges.num)
+		return;
+
+	F4 = node_to_amd_nb(0)->link;
+	if (!F4)
+		return;
+
+	if (pci_read_config_dword(F4, 0x164, &val))
+		return;
+
+	if (val & BIT(2))
+		return;
+
+	on_each_cpu(__fix_erratum_688, NULL, 0);
+}
+
 static __init int init_amd_nbs(void)
 {
 	amd_cache_northbridges();
 	amd_cache_gart();
 
+	fix_erratum_688();
+
 	return 0;
 }
 

-- 
Regards/Gruss,
    Boris.

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