linux-kernel - [RFC PATCH] x86/mce: Check MCi_STATUS[MISCV] for usable addr on Intel only

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Date:   Tue, 18 Apr 2017 20:39:24 +0200
From:   Borislav Petkov <bp@...e.de>
To:     Yazen Ghannam <yazen.ghannam@....com>
Cc:     Tony Luck <tony.luck@...el.com>,
        linux-edac <linux-edac@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>
Subject: [RFC PATCH] x86/mce: Check MCi_STATUS[MISCV] for usable addr on
 Intel only

mce_usable_address() does a bunch of basic sanity checks to verify
whether the address reported with the error is usable for further
processing. However, we do check MCi_STATUS[MISCV] and that is not
needed on AMD as that bit says that there's additional information about
the logged error in the MCi_MISCj banks.

But we don't need that to know whether the address is usable - we only
need to know whether the physical address is valid - i.e., ADDRV.

 [ On Intel the MISCV bit is needed to perform additional checks to
   determine whether the reported address is a physical one, etc. ]

Signed-off-by: Borislav Petkov <bp@...e.de>
Cc: "Ghannam, Yazen" <Yazen.Ghannam@....com>
---

Right, so I think we don't need to look at MISCV on AMD to check whether
the address is usable because ADDRV already denotes that MCi_ADDR has
the physical address. Yes?

 arch/x86/kernel/cpu/mcheck/mce.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index d409e21ec275..5abd4bf73d6e 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -480,17 +480,22 @@ static void mce_report_event(struct pt_regs *regs)
  */
 static int mce_usable_address(struct mce *m)
 {
-	if (!(m->status & MCI_STATUS_MISCV) || !(m->status & MCI_STATUS_ADDRV))
+	if (!(m->status & MCI_STATUS_ADDRV))
 		return 0;

 	/* Checks after this one are Intel-specific: */
 	if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL)
 		return 1;

+	if (!(m->status & MCI_STATUS_MISCV))
+		return 0;
+
 	if (MCI_MISC_ADDR_LSB(m->misc) > PAGE_SHIFT)
 		return 0;
+
 	if (MCI_MISC_ADDR_MODE(m->misc) != MCI_MISC_ADDR_PHYS)
 		return 0;
+
 	return 1;
 }

-- 
2.11.0

-- 
Regards/Gruss,
    Boris.

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