[tip:ras/core] x86/mce: Check MCi_STATUS[MISCV] for usable addr on Intel only

[tip-bot for Borislav Petkov]

Commit-ID:  c6a9583fb41c8bd017f643d5bc90a0fe0a92fe43
Gitweb:     http://git.kernel.org/tip/c6a9583fb41c8bd017f643d5bc90a0fe0a92fe43
Author:     Borislav Petkov <bp@xxxxxxx>
AuthorDate: Tue, 18 Apr 2017 20:39:24 +0200
Committer:  Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Wed, 19 Apr 2017 12:04:46 +0200

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@xxxxxxx>
Cc: Yazen Ghannam <yazen.ghannam@xxxxxxx>
Cc: Tony Luck <tony.luck@xxxxxxxxx>
Cc: linux-edac <linux-edac@xxxxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/20170418183924.6agjkebilwqj26or@xxxxxxx
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>

---
 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 9d41ec8..4a29f74 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -491,17 +491,22 @@ 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;
 }