Date: Mon, 8 Feb 2021 17:33:22 +0200 From: Konstantin Belousov <kostikbel@gmail.com> To: Mark Johnston <markj@freebsd.org> Cc: Alan Somers <asomers@freebsd.org>, Matthew Macy <mmacy@freebsd.org>, FreeBSD Stable ML <stable@freebsd.org> Subject: Re: Page fault in _mca_init during startup Message-ID: <YCFZwi%2BawXj7qHvD@kib.kiev.ua> In-Reply-To: <YCFS39xe4bUhMEQr@raichu> References: <YByYZDEbGlSsgcwv@kib.kiev.ua> <CAOtMX2hY2WFvtuG2U_4PCqL8fPTqmVPKgHkmh-A88GBz85obNw@mail.gmail.com> <YBywA/5PHEqDJ4J4@kib.kiev.ua> <CAOtMX2iXXgBuXWVBmS3oorZd7UxTgvYPPh9eTSfTNvTn8q_TSw@mail.gmail.com> <YB1ZDMGCOL%2BJ0SWE@kib.kiev.ua> <CAOtMX2g1Nz8BzRUhbeygTAniVObCTT2F0_U3se2kKOhnKJbjAQ@mail.gmail.com> <YB1%2BiUxs1ZITHaR/@kib.kiev.ua> <CAOtMX2iF7QCNvNfU2CSseH-mgNGudZ_TCVoXuoF%2BPE9sk_TB6Q@mail.gmail.com> <YCBnJB104tqztbYE@kib.kiev.ua> <YCFS39xe4bUhMEQr@raichu>
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On Mon, Feb 08, 2021 at 10:03:59AM -0500, Mark Johnston wrote:
> On Mon, Feb 08, 2021 at 12:18:12AM +0200, Konstantin Belousov wrote:
> > On Sun, Feb 07, 2021 at 02:33:11PM -0700, Alan Somers wrote:
> > > Upgrading the BIOS fixed the problem, by clearing the MCG_CMCI_P bit on all
> > > processors. I don't have strong opinions about whether we should commit
> > > kib's patch too. Kib, what do you think?
> >
> > The patch causes some memory over-use.
> >
> > If this issue is not too widely experienced, I prefer to not commit the patch.
>
> Couldn't we short-circuit cmci_monitor() if the BSP did not allocate
> anything?
>
> diff --git a/sys/x86/x86/mca.c b/sys/x86/x86/mca.c
> index 03100e77d45..0619a41b128 100644
> --- a/sys/x86/x86/mca.c
> +++ b/sys/x86/x86/mca.c
> @@ -1070,6 +1070,13 @@ cmci_monitor(int i)
>
> KASSERT(i < mca_banks, ("CPU %d has more MC banks", PCPU_GET(cpuid)));
>
> + /*
> + * It is possible for some APs to report CMCI support even if the BSP
> + * does not, apparently due to a BIOS bug.
> + */
> + if (cmc_state == NULL)
> + return;
> +
> ctl = rdmsr(MSR_MC_CTL2(i));
> if (ctl & MC_CTL2_CMCI_EN)
> /* Already monitored by another CPU. */
> @@ -1114,6 +1121,10 @@ cmci_resume(int i)
>
> KASSERT(i < mca_banks, ("CPU %d has more MC banks", PCPU_GET(cpuid)));
>
> + /* See cmci_monitor(). */
> + if (cmc_state == NULL)
> + return;
> +
> /* Ignore banks not monitored by this CPU. */
> if (!(PCPU_GET(cmci_mask) & 1 << i))
> return;
I think something should be printed in this case, at least once.
I believe printf() already works, because spin locks do.
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