linux-kernel - Re: [PATCH] mm/vmalloc: track which page-table levels were modified

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Date:   Wed, 3 Jun 2020 16:23:11 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Joerg Roedel <jroedel@...e.de>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/vmalloc: track which page-table levels were modified

On Mon, Jun 01, 2020 at 09:52:22PM -0700, Joerg Roedel wrote:
> Track at which levels in the page-table entries were modified by
> vmap/vunmap.
> 
> After the page-table has been modified, use that information do decide
> whether the new arch_sync_kernel_mappings() needs to be called.
> 
> [akpm@...ux-foundation.org: map_kernel_range_noflush() needs the arch_sync_kernel_mappings() call]
> Signed-off-by: Joerg Roedel <jroedel@...e.de>
> Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
> Acked-by: Andy Lutomirski <luto@...nel.org>
> Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> Cc: Arnd Bergmann <arnd@...db.de>
> Cc: Christoph Hellwig <hch@....de>
> Cc: Dave Hansen <dave.hansen@...ux.intel.com>
> Cc: "H . Peter Anvin" <hpa@...or.com>
> Cc: Ingo Molnar <mingo@...e.hu>
> Cc: Matthew Wilcox (Oracle) <willy@...radead.org>
> Cc: Michal Hocko <mhocko@...nel.org>
> Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>
> Cc: Steven Rostedt (VMware) <rostedt@...dmis.org>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Vlastimil Babka <vbabka@...e.cz>
> Link: http://lkml.kernel.org/r/20200515140023.25469-3-joro@8bytes.org
> Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>

This patch causes crashes with all my ppc64 boot tests, in various
locations depending on the platform. Reverting it together with its
companion "mm/ioremap: track which page-table levels were modified"
fixes the problem.

Various logs are at
https://kerneltests.org/builders/qemu-ppc64-master/builds/1442/steps/qemubuildcommand/logs/stdio

Just for completeness, bisect log attached.

Guenter

---
# bad: [f6aee505c71bbb035dde146caf5a6abbf3ccbe47] Merge tag 'x86-timers-2020-06-03' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
# good: [b23c4771ff62de8ca9b5e4a2d64491b2fb6f8f69] Merge tag 'docs-5.8' of git://git.lwn.net/linux
git bisect start 'HEAD' 'b23c4771ff62'
# good: [c41219fda6e04255c44d37fd2c0d898c1c46abf1] Merge tag 'drm-intel-next-fixes-2020-05-20' of git://anongit.freedesktop.org/drm/drm-intel into drm-next
git bisect good c41219fda6e04255c44d37fd2c0d898c1c46abf1
# bad: [1966391fa576e1fb2701be8bcca197d8f72737b7] mm/migrate.c: attach_page_private already does the get_page
git bisect bad 1966391fa576e1fb2701be8bcca197d8f72737b7
# bad: [c5d6c13843880ad0112f0513f3eb041b258be66e] Merge tag 'mmc-v5.8' of git://git.kernel.org/pub/scm/linux/kernel/git/ulfh/mmc
git bisect bad c5d6c13843880ad0112f0513f3eb041b258be66e
# bad: [94709049fb8442fb2f7b91fbec3c2897a75e18df] Merge branch 'akpm' (patches from Andrew)
git bisect bad 94709049fb8442fb2f7b91fbec3c2897a75e18df
# good: [a29adb6209cead1f6c34a8d72481fb183bfc2d68] mm: rename vmap_page_range to map_kernel_range
git bisect good a29adb6209cead1f6c34a8d72481fb183bfc2d68
# good: [56446efab9ce4961fe0fe6bbc5bc66374b08b9f3] Merge branch 'uaccess.__copy_from_user' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
git bisect good 56446efab9ce4961fe0fe6bbc5bc66374b08b9f3
# good: [17839856fd588f4ab6b789f482ed3ffd7c403e1f] gup: document and work around "COW can break either way" issue
git bisect good 17839856fd588f4ab6b789f482ed3ffd7c403e1f
# good: [ebcdd3074a729f9ba351278e1b42d7ae7fcdf236] arm64: use __vmalloc_node in arch_alloc_vmap_stack
git bisect good ebcdd3074a729f9ba351278e1b42d7ae7fcdf236
# bad: [86cf69f1d893d48fdb0382a940f2523409406423] x86/mm/32: implement arch_sync_kernel_mappings()
git bisect bad 86cf69f1d893d48fdb0382a940f2523409406423
# good: [d8626138009ba58ae2c22356966c2edaa1f1c3b5] mm: add functions to track page directory modifications
git bisect good d8626138009ba58ae2c22356966c2edaa1f1c3b5
# bad: [6c0c7d2b365b21a413f6d75772a8a4a2c7d36916] mm/ioremap: track which page-table levels were modified
git bisect bad 6c0c7d2b365b21a413f6d75772a8a4a2c7d36916
# bad: [2ba3e6947aed9bb9575eb1603c0ac6e39185d32a] mm/vmalloc: track which page-table levels were modified
git bisect bad 2ba3e6947aed9bb9575eb1603c0ac6e39185d32a
# first bad commit: [2ba3e6947aed9bb9575eb1603c0ac6e39185d32a] mm/vmalloc: track which page-table levels were modified