From: Will Deacon <will@kernel.org>
To: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: James Morris <jmorris@namei.org>, Sasha Levin <sashal@kernel.org>,
"Eric W. Biederman" <ebiederm@xmission.com>,
kexec mailing list <kexec@lists.infradead.org>,
LKML <linux-kernel@vger.kernel.org>,
Jonathan Corbet <corbet@lwn.net>,
Catalin Marinas <catalin.marinas@arm.com>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
Marc Zyngier <maz@kernel.org>, James Morse <james.morse@arm.com>,
Vladimir Murzin <vladimir.murzin@arm.com>,
Matthias Brugger <matthias.bgg@gmail.com>,
linux-mm <linux-mm@kvack.org>,
Mark Rutland <mark.rutland@arm.com>,
steve.capper@arm.com, rfontana@redhat.com,
Thomas Gleixner <tglx@linutronix.de>,
Selin Dag <selindag@gmail.com>,
Tyler Hicks <tyhicks@linux.microsoft.com>,
Pingfan Liu <kernelfans@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
madvenka@linux.microsoft.com
Subject: Re: [PATCH v17 08/15] arm64: kexec: configure EL2 vectors for kexec
Date: Thu, 30 Sep 2021 09:16:07 +0100 [thread overview]
Message-ID: <20210930081607.GA23250@willie-the-truck> (raw)
In-Reply-To: <CA+CK2bDw3A7FkZoQbB-AQWHj89Azqjrm12WFQVcfQjS+2Tmgyg@mail.gmail.com>
On Wed, Sep 29, 2021 at 11:54:55PM -0400, Pasha Tatashin wrote:
> > > +/* Allocates pages for kexec page table */
> > > +static void *kexec_page_alloc(void *arg)
> > > +{
> > > + struct kimage *kimage = (struct kimage *)arg;
> > > + struct page *page = kimage_alloc_control_pages(kimage, 0);
> > > +
> > > + if (!page)
> > > + return NULL;
> > > +
> > > + memset(page_address(page), 0, PAGE_SIZE);
> >
> > Hmm, I think we might be missing barriers here to ensure that the zeroes
> > are visible to the page-table walker before we plumb the page into the
> > page-table.
> >
> > Usually, that's taken care of by the smp_wmb() in __pXX_alloc() but I
> > can't see that here. Is it hiding?
>
> Based on the comment in __pte_alloc() that smp_wmb() is needed in
> order to synchronize pte setup with other cpus prior to making it
> visible to them. This is not needed here. First, by the time these
> page tables are used the other cpus are offlined (kexec reboot code is
> single threaded). Second, we never insert any entry into a page table
> that is actively used by any cpu.
I think the comment there is wrong, but the barrier is still necessary.
How else do you guarantee that the page-table walker reads the zeroes from
the memset?
Will
next prev parent reply other threads:[~2021-09-30 8:16 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-16 23:13 [PATCH v17 00/15] arm64: MMU enabled kexec relocation Pasha Tatashin
2021-09-16 23:13 ` [PATCH v17 01/15] arm64: kernel: add helper for booted at EL2 and not VHE Pasha Tatashin
2021-09-16 23:13 ` [PATCH v17 02/15] arm64: trans_pgd: hibernate: Add trans_pgd_copy_el2_vectors Pasha Tatashin
2021-09-16 23:13 ` [PATCH v17 03/15] arm64: hibernate: abstract ttrb0 setup function Pasha Tatashin
2021-09-16 23:13 ` [PATCH v17 04/15] arm64: kexec: flush image and lists during kexec load time Pasha Tatashin
2021-09-16 23:13 ` [PATCH v17 05/15] arm64: kexec: skip relocation code for inplace kexec Pasha Tatashin
2021-09-29 12:13 ` Will Deacon
2021-09-30 2:44 ` Pasha Tatashin
2021-09-16 23:13 ` [PATCH v17 06/15] arm64: kexec: Use dcache ops macros instead of open-coding Pasha Tatashin
2021-09-16 23:13 ` [PATCH v17 07/15] arm64: kexec: pass kimage as the only argument to relocation function Pasha Tatashin
2021-09-16 23:13 ` [PATCH v17 08/15] arm64: kexec: configure EL2 vectors for kexec Pasha Tatashin
2021-09-29 12:35 ` Will Deacon
2021-09-30 3:54 ` Pasha Tatashin
2021-09-30 8:16 ` Will Deacon [this message]
2021-09-30 11:59 ` Pasha Tatashin
2021-09-16 23:13 ` [PATCH v17 09/15] arm64: kexec: relocate in EL1 mode Pasha Tatashin
2021-09-16 23:13 ` [PATCH v17 10/15] arm64: kexec: use ld script for relocation function Pasha Tatashin
2021-09-29 12:45 ` Will Deacon
2021-09-30 3:57 ` Pasha Tatashin
2021-09-30 4:08 ` Pasha Tatashin
2021-09-16 23:13 ` [PATCH v17 11/15] arm64: kexec: install a copy of the linear-map Pasha Tatashin
2021-09-16 23:13 ` [PATCH v17 12/15] arm64: kexec: keep MMU enabled during kexec relocation Pasha Tatashin
2021-09-16 23:13 ` [PATCH v17 13/15] arm64: kexec: remove the pre-kexec PoC maintenance Pasha Tatashin
2021-09-16 23:13 ` [PATCH v17 14/15] arm64: kexec: remove cpu-reset.h Pasha Tatashin
2021-09-16 23:13 ` [PATCH v17 15/15] arm64: trans_pgd: remove trans_pgd_map_page() Pasha Tatashin
2021-09-29 16:43 ` Catalin Marinas
2021-09-30 4:12 ` Pasha Tatashin
2021-09-29 12:49 ` [PATCH v17 00/15] arm64: MMU enabled kexec relocation Will Deacon
2021-09-30 4:13 ` Pasha Tatashin
2021-09-29 17:21 ` Catalin Marinas
2021-09-30 4:13 ` Pasha Tatashin
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