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Message-ID: <20180819103415.289e374c@canb.auug.org.au>
Date: Sun, 19 Aug 2018 10:34:15 +1000
From: Stephen Rothwell <sfr@...b.auug.org.au>
To: Dan Williams <dan.j.williams@...el.com>
Cc: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...e.hu>,
"H. Peter Anvin" <hpa@...or.com>,
Peter Zijlstra <peterz@...radead.org>,
Linux-Next Mailing List <linux-next@...r.kernel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Borislav Petkov <bp@...e.de>
Subject: Re: linux-next: manual merge of the nvdimm tree with the tip tree
Hi all,
On Tue, 26 Jun 2018 12:18:53 +1000 Stephen Rothwell <sfr@...b.auug.org.au> wrote:
>
> Today's linux-next merge of the nvdimm tree got a conflict in:
>
> arch/x86/kernel/cpu/mcheck/mce.c
>
> between commit:
>
> d3d6923cd1ae ("x86/mce: Carve out the crashing_cpu check")
>
> from the tip tree and commit:
>
> f6785eac562b ("x86/memory_failure: Introduce {set,clear}_mce_nospec()")
>
> from the nvdimm tree.
>
> I fixed it up (see below) and can carry the fix as necessary. This
> is now fixed as far as linux-next is concerned, but any non trivial
> conflicts should be mentioned to your upstream maintainer when your tree
> is submitted for merging. You may also want to consider cooperating
> with the maintainer of the conflicting tree to minimise any particularly
> complex conflicts.
>
> --
> Cheers,
> Stephen Rothwell
>
> diff --cc arch/x86/kernel/cpu/mcheck/mce.c
> index 9a16f15f79eb,a0fbf0a8b7e6..000000000000
> --- a/arch/x86/kernel/cpu/mcheck/mce.c
> +++ b/arch/x86/kernel/cpu/mcheck/mce.c
> @@@ -1076,129 -1070,6 +1072,100 @@@ static int do_memory_failure(struct mc
> return ret;
> }
>
> - #ifndef mce_unmap_kpfn
> - static void mce_unmap_kpfn(unsigned long pfn)
> - {
> - unsigned long decoy_addr;
> -
> - /*
> - * Unmap this page from the kernel 1:1 mappings to make sure
> - * we don't log more errors because of speculative access to
> - * the page.
> - * We would like to just call:
> - * set_memory_np((unsigned long)pfn_to_kaddr(pfn), 1);
> - * but doing that would radically increase the odds of a
> - * speculative access to the poison page because we'd have
> - * the virtual address of the kernel 1:1 mapping sitting
> - * around in registers.
> - * Instead we get tricky. We create a non-canonical address
> - * that looks just like the one we want, but has bit 63 flipped.
> - * This relies on set_memory_np() not checking whether we passed
> - * a legal address.
> - */
> -
> - decoy_addr = (pfn << PAGE_SHIFT) + (PAGE_OFFSET ^ BIT(63));
> -
> - if (set_memory_np(decoy_addr, 1))
> - pr_warn("Could not invalidate pfn=0x%lx from 1:1 map\n", pfn);
> - }
> - #endif
> -
> -
> +/*
> + * Cases where we avoid rendezvous handler timeout:
> + * 1) If this CPU is offline.
> + *
> + * 2) If crashing_cpu was set, e.g. we're entering kdump and we need to
> + * skip those CPUs which remain looping in the 1st kernel - see
> + * crash_nmi_callback().
> + *
> + * Note: there still is a small window between kexec-ing and the new,
> + * kdump kernel establishing a new #MC handler where a broadcasted MCE
> + * might not get handled properly.
> + */
> +static bool __mc_check_crashing_cpu(int cpu)
> +{
> + if (cpu_is_offline(cpu) ||
> + (crashing_cpu != -1 && crashing_cpu != cpu)) {
> + u64 mcgstatus;
> +
> + mcgstatus = mce_rdmsrl(MSR_IA32_MCG_STATUS);
> + if (mcgstatus & MCG_STATUS_RIPV) {
> + mce_wrmsrl(MSR_IA32_MCG_STATUS, 0);
> + return true;
> + }
> + }
> + return false;
> +}
> +
> +static void __mc_scan_banks(struct mce *m, struct mce *final,
> + unsigned long *toclear, unsigned long *valid_banks,
> + int no_way_out, int *worst)
> +{
> + struct mca_config *cfg = &mca_cfg;
> + int severity, i;
> +
> + for (i = 0; i < cfg->banks; i++) {
> + __clear_bit(i, toclear);
> + if (!test_bit(i, valid_banks))
> + continue;
> +
> + if (!mce_banks[i].ctl)
> + continue;
> +
> + m->misc = 0;
> + m->addr = 0;
> + m->bank = i;
> +
> + m->status = mce_rdmsrl(msr_ops.status(i));
> + if (!(m->status & MCI_STATUS_VAL))
> + continue;
> +
> + /*
> + * Corrected or non-signaled errors are handled by
> + * machine_check_poll(). Leave them alone, unless this panics.
> + */
> + if (!(m->status & (cfg->ser ? MCI_STATUS_S : MCI_STATUS_UC)) &&
> + !no_way_out)
> + continue;
> +
> + /* Set taint even when machine check was not enabled. */
> + add_taint(TAINT_MACHINE_CHECK, LOCKDEP_NOW_UNRELIABLE);
> +
> + severity = mce_severity(m, cfg->tolerant, NULL, true);
> +
> + /*
> + * When machine check was for corrected/deferred handler don't
> + * touch, unless we're panicking.
> + */
> + if ((severity == MCE_KEEP_SEVERITY ||
> + severity == MCE_UCNA_SEVERITY) && !no_way_out)
> + continue;
> +
> + __set_bit(i, toclear);
> +
> + /* Machine check event was not enabled. Clear, but ignore. */
> + if (severity == MCE_NO_SEVERITY)
> + continue;
> +
> + mce_read_aux(m, i);
> +
> + /* assuming valid severity level != 0 */
> + m->severity = severity;
> +
> + mce_log(m);
> +
> + if (severity > *worst) {
> + *final = *m;
> + *worst = severity;
> + }
> + }
> +
> + /* mce_clear_state will clear *final, save locally for use later */
> + *m = *final;
> +}
> +
> /*
> * The actual machine check handler. This only handles real
> * exceptions when something got corrupted coming in through int 18.
This is now a conflict between Linus' tree and the nvdimm tree.
--
Cheers,
Stephen Rothwell
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