[ Upstream commit f19501aa07f18268ab14f458b51c1c6b7f72a134 ]
There has been a lurking "TBD" in the machine check poll routine ever since it was first split out from the machine check handler. The potential issue is that the poll routine may have just begun a read from the STATUS register in a machine check bank when the hardware logs an error in that bank and signals a machine check.
That race used to be pretty small back when machine checks were broadcast, but the addition of local machine check means that the poll code could continue running and clear the error from the bank before the local machine check handler on another CPU gets around to reading it.
Fix the code to be sure to only process errors that need to be processed in the poll code, leaving other logged errors alone for the machine check handler to find and process.
[ bp: Massage a bit and flip the "== 0" check to the usual !(..) test. ]
Fixes: b79109c3bbcf ("x86, mce: separate correct machine check poller and fatal exception handler") Fixes: ed7290d0ee8f ("x86, mce: implement new status bits") Reported-by: Ashok Raj ashok.raj@intel.com Signed-off-by: Tony Luck tony.luck@intel.com Signed-off-by: Borislav Petkov bp@suse.de Cc: Ashok Raj ashok.raj@intel.com Cc: "H. Peter Anvin" hpa@zytor.com Cc: Ingo Molnar mingo@redhat.com Cc: linux-edac linux-edac@vger.kernel.org Cc: Thomas Gleixner tglx@linutronix.de Cc: x86-ml x86@kernel.org Cc: Yazen Ghannam Yazen.Ghannam@amd.com Link: https://lkml.kernel.org/r/20190312170938.GA23035@agluck-desk Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/kernel/cpu/mcheck/mce.c | 44 +++++++++++++++++++++++++++----- 1 file changed, 37 insertions(+), 7 deletions(-)
diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c index f9e7096b1804d..45bd926359f62 100644 --- a/arch/x86/kernel/cpu/mcheck/mce.c +++ b/arch/x86/kernel/cpu/mcheck/mce.c @@ -711,19 +711,49 @@ bool machine_check_poll(enum mcp_flags flags, mce_banks_t *b)
barrier(); m.status = mce_rdmsrl(msr_ops.status(i)); + + /* If this entry is not valid, ignore it */ if (!(m.status & MCI_STATUS_VAL)) continue;
/* - * Uncorrected or signalled events are handled by the exception - * handler when it is enabled, so don't process those here. - * - * TBD do the same check for MCI_STATUS_EN here? + * If we are logging everything (at CPU online) or this + * is a corrected error, then we must log it. */ - if (!(flags & MCP_UC) && - (m.status & (mca_cfg.ser ? MCI_STATUS_S : MCI_STATUS_UC))) - continue; + if ((flags & MCP_UC) || !(m.status & MCI_STATUS_UC)) + goto log_it; + + /* + * Newer Intel systems that support software error + * recovery need to make additional checks. Other + * CPUs should skip over uncorrected errors, but log + * everything else. + */ + if (!mca_cfg.ser) { + if (m.status & MCI_STATUS_UC) + continue; + goto log_it; + } + + /* Log "not enabled" (speculative) errors */ + if (!(m.status & MCI_STATUS_EN)) + goto log_it; + + /* + * Log UCNA (SDM: 15.6.3 "UCR Error Classification") + * UC == 1 && PCC == 0 && S == 0 + */ + if (!(m.status & MCI_STATUS_PCC) && !(m.status & MCI_STATUS_S)) + goto log_it; + + /* + * Skip anything else. Presumption is that our read of this + * bank is racing with a machine check. Leave the log alone + * for do_machine_check() to deal with it. + */ + continue;
+log_it: error_seen = true;
mce_read_aux(&m, i);