linux-kernel - Re: [PATCH v3 5/6] x86/MCE: Save MCA control bits that get set in hardware

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Message-ID: <20190516203456.GD21857@zn.tnic>
Date:   Thu, 16 May 2019 22:34:56 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     "Ghannam, Yazen" <Yazen.Ghannam@....com>
Cc:     "Luck, Tony" <tony.luck@...el.com>,
        "linux-edac@...r.kernel.org" <linux-edac@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>
Subject: Re: [PATCH v3 5/6] x86/MCE: Save MCA control bits that get set in
 hardware

On Thu, May 16, 2019 at 08:20:58PM +0000, Ghannam, Yazen wrote:
> We don't actually know if there are bits set in hardware until we read
> it back. So I don't think this is adding anything new.

Bah, of course. We need to read it first (pasting the whole function).
Now, __mcheck_cpu_init_clear_banks() gets called when we change
configuration too, in mce_cpu_restart() and if we do it this way, we'll
be rereading MCi_CTL each time but I don't see anything wrong with that.

Hmmm?

static void __mcheck_cpu_init_clear_banks(void)
{
        struct mce_bank *mce_banks = this_cpu_read(mce_banks_array);
        int i;

        for (i = 0; i < this_cpu_read(mce_num_banks); i++) {
                struct mce_bank *b = &mce_banks[i];

                rdmsrl(msr_ops.ctl(i), b->ctl);

                /* Bank is initialized if bits are set in hardware. */
                b->init = !!b->ctl;
                if (b->init) {
                        wrmsrl(msr_ops.ctl(i), b->ctl);
                        wrmsrl(msr_ops.status(i), 0);
                }

        }
}

-- 
Regards/Gruss,
    Boris.

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