> -----Original Message----- > From: Borislav Petkov <b...@alien8.de> > Sent: Wednesday, April 10, 2019 11:41 AM > To: Ghannam, Yazen <yazen.ghan...@amd.com> > Cc: linux-e...@vger.kernel.org; linux-kernel@vger.kernel.org; > tony.l...@intel.com; x...@kernel.org > Subject: Re: [PATCH RESEND 2/5] x86/MCE: Handle MCA controls in a per_cpu way > > On Wed, Apr 10, 2019 at 04:36:30PM +0000, Ghannam, Yazen wrote: > > We have this case on AMD Family 17h with Bank 4. The hardware enforces > > this bank to be Read-as-Zero/Writes-Ignored. > > > > This behavior is enforced whether the bank is in the middle or at the > > end. > > Does num_banks contain the disabled bank? If so, then it will work. >
Yes, unused banks in the middle are counted in the MCG_CAP[Count] value. > > I'm thinking to redo the sysfs interface for banks in another patch > > set. I could include a new file to indicate enabled/disabled, or maybe > > just update the documentation to describe this case. > > No, the write to the bank controls should fail on a disabled bank. > Okay, so you're saying the sysfs access should fail if a bank is disabled. Is that correct? Does "disabled" mean one or both of these? Unused = RAZ/WI in hardware Uninitialized = Not initialized by kernel due to quirks, etc. For an unused bank, it doesn't hurt to write MCA_CTL, but really there's no reason to do so and go through mce_restart(). For an uninitialized bank, should we prevent users from overriding the kernel's settings? Thanks, Yazen
