From: Dan Williams <dan.j.williams@intel.com>
To: Andy Lutomirski <luto@amacapital.net>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Andy Lutomirski <luto@kernel.org>,
Dave Hansen <dave.hansen@linux.intel.com>,
Peter Zijlstra <peterz@infradead.org>,
Borislav Petkov <bp@alien8.de>, stable <stable@vger.kernel.org>,
X86 ML <x86@kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Subject: Re: [PATCH] x86/mm/pat: Fix missing preemption disable for __native_flush_tlb()
Date: Sat, 10 Nov 2018 16:31:45 -0800 [thread overview]
Message-ID: <CAPcyv4i7m+FuwFKLyQ6StNL2BCiNv7=O_Y9J4Ojqek7nC9mNjw@mail.gmail.com> (raw)
In-Reply-To: <9DFD717D-857D-493D-A606-B635D72BAC21@amacapital.net>
[ added Kirill ]
On Sat, Nov 10, 2018 at 4:19 PM Andy Lutomirski <luto@amacapital.net> wrote:
> > On Nov 10, 2018, at 3:57 PM, Dan Williams <dan.j.williams@intel.com> wrote:
> >
> >> On Fri, Nov 9, 2018 at 4:22 PM Andy Lutomirski <luto@amacapital.net> wrote:
> >>
> >>
> >>
> >>> On Nov 9, 2018, at 4:05 PM, Dan Williams <dan.j.williams@intel.com> wrote:
> >>>
> >>> Commit f77084d96355 "x86/mm/pat: Disable preemption around
> >>> __flush_tlb_all()" addressed a case where __flush_tlb_all() is called
> >>> without preemption being disabled. It also left a warning to catch other
> >>> cases where preemption is not disabled. That warning triggers for the
> >>> memory hotplug path which is also used for persistent memory enabling:
> >>
> >> I don’t think I agree with the patch. If you call __flush_tlb_all() in a context where you might be *migrated*, then there’s a bug. We could change the code to allow this particular use by checking that we haven’t done SMP init yet, perhaps.
> >
> > Hmm, are saying the entire kernel_physical_mapping_init() sequence
> > needs to run with pre-emption disabled?
>
> If it indeed can run late in boot or after boot, then it sure looks buggy. Either the __flush_tlb_all() should be removed or it should be replaced with flush_tlb_kernel_range(). It’s unclear to me why a flush is needed at all, but if it’s needed, surely all CPUs need flushing.
Yeah, I don't think __flush_tlb_all() is needed at
kernel_physical_mapping_init() time, and at
kernel_physical_mapping_remove() time we do a full flush_tlb_all().
Kirill?
next prev parent reply other threads:[~2018-11-11 0:32 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-10 0:05 [PATCH] x86/mm/pat: Fix missing preemption disable for __native_flush_tlb() Dan Williams
2018-11-10 0:22 ` Andy Lutomirski
2018-11-10 23:57 ` Dan Williams
2018-11-11 0:19 ` Andy Lutomirski
2018-11-11 0:31 ` Dan Williams [this message]
2018-11-12 19:07 ` Dave Hansen
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