From: Chris Wilson <chris@chris-wilson.co.uk>
To: Joerg Roedel <jroedel@suse.de>
Cc: linux-kernel@vger.kernel.org, intel-gfx@lists.freedesktop.org,
linux-mm@kvack.org, Pavel Machek <pavel@ucw.cz>,
Andrew Morton <akpm@linux-foundation.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Dave Airlie <airlied@redhat.com>,
Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
Rodrigo Vivi <rodrigo.vivi@intel.com>,
David Vrabel <david.vrabel@citrix.com>,
stable@vger.kernel.org
Subject: Re: [PATCH 1/4] mm: Export flush_vm_area() to sync the PTEs upon construction
Date: Fri, 21 Aug 2020 10:54:22 +0100 [thread overview]
Message-ID: <159800366215.29194.8455636122843151159@build.alporthouse.com> (raw)
In-Reply-To: <20200821095129.GF3354@suse.de>
Quoting Joerg Roedel (2020-08-21 10:51:29)
> On Fri, Aug 21, 2020 at 09:50:08AM +0100, Chris Wilson wrote:
> > The alloc_vm_area() is another method for drivers to
> > vmap/map_kernel_range that uses apply_to_page_range() rather than the
> > direct vmalloc walkers. This is missing the page table modification
> > tracking, and the ability to synchronize the PTE updates afterwards.
> > Provide flush_vm_area() for the users of alloc_vm_area() that assumes
> > the worst and ensures that the page directories are correctly flushed
> > upon construction.
> >
> > The impact is most pronounced on x86_32 due to the delayed set_pmd().
> >
> > Reported-by: Pavel Machek <pavel@ucw.cz>
> > References: 2ba3e6947aed ("mm/vmalloc: track which page-table levels were modified")
> > References: 86cf69f1d893 ("x86/mm/32: implement arch_sync_kernel_mappings()")
> > Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> > Cc: Andrew Morton <akpm@linux-foundation.org>
> > Cc: Joerg Roedel <jroedel@suse.de>
> > Cc: Linus Torvalds <torvalds@linux-foundation.org>
> > Cc: Dave Airlie <airlied@redhat.com>
> > Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
> > Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> > Cc: Pavel Machek <pavel@ucw.cz>
> > Cc: David Vrabel <david.vrabel@citrix.com>
> > Cc: <stable@vger.kernel.org> # v5.8+
> > ---
> > include/linux/vmalloc.h | 1 +
> > mm/vmalloc.c | 16 ++++++++++++++++
> > 2 files changed, 17 insertions(+)
> >
> > diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
> > index 0221f852a7e1..a253b27df0ac 100644
> > --- a/include/linux/vmalloc.h
> > +++ b/include/linux/vmalloc.h
> > @@ -204,6 +204,7 @@ static inline void set_vm_flush_reset_perms(void *addr)
> >
> > /* Allocate/destroy a 'vmalloc' VM area. */
> > extern struct vm_struct *alloc_vm_area(size_t size, pte_t **ptes);
> > +extern void flush_vm_area(struct vm_struct *area);
> > extern void free_vm_area(struct vm_struct *area);
> >
> > /* for /dev/kmem */
> > diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> > index b482d240f9a2..c41934486031 100644
> > --- a/mm/vmalloc.c
> > +++ b/mm/vmalloc.c
> > @@ -3078,6 +3078,22 @@ struct vm_struct *alloc_vm_area(size_t size, pte_t **ptes)
> > }
> > EXPORT_SYMBOL_GPL(alloc_vm_area);
> >
> > +void flush_vm_area(struct vm_struct *area)
> > +{
> > + unsigned long addr = (unsigned long)area->addr;
> > +
> > + /* apply_to_page_range() doesn't track the damage, assume the worst */
> > + if (ARCH_PAGE_TABLE_SYNC_MASK & (PGTBL_PTE_MODIFIED |
> > + PGTBL_PMD_MODIFIED |
> > + PGTBL_PUD_MODIFIED |
> > + PGTBL_P4D_MODIFIED |
> > + PGTBL_PGD_MODIFIED))
> > + arch_sync_kernel_mappings(addr, addr + area->size);
>
> This should happen in __apply_to_page_range() directly and look like
> this:
Ok. I thought it had to be after assigning the *ptep. If we apply the
sync first, do not have to worry about PGTBL_PTE_MODIFIED from the
*ptep?
-Chris
next prev parent reply other threads:[~2020-08-21 9:54 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-21 8:50 [PATCH 1/4] mm: Export flush_vm_area() to sync the PTEs upon construction Chris Wilson
2020-08-21 8:50 ` [PATCH 2/4] drm/i915/gem: Sync the vmap " Chris Wilson
2020-08-21 12:41 ` Linus Torvalds
2020-08-21 13:01 ` Chris Wilson
2020-08-21 8:50 ` [PATCH 3/4] drm/i915/gem: Use set_pte_at() for assigning the vmapped PTE Chris Wilson
2020-08-21 8:50 ` [PATCH 4/4] drm/i915/gem: Replace reloc chain with terminator on error unwind Chris Wilson
2020-08-21 9:51 ` [PATCH 1/4] mm: Export flush_vm_area() to sync the PTEs upon construction Joerg Roedel
2020-08-21 9:54 ` Chris Wilson [this message]
2020-08-21 10:22 ` Joerg Roedel
2020-08-21 10:36 ` Chris Wilson
2020-08-21 10:09 ` [PATCH] mm: Track page table modifications in __apply_to_page_range() construction Joerg Roedel
2020-08-21 10:13 ` Chris Wilson
2020-08-21 10:23 ` Joerg Roedel
2020-08-21 10:39 ` Chris Wilson
2020-08-21 11:38 ` Chris Wilson
2020-08-21 12:18 ` Joerg Roedel
2020-08-21 10:53 ` Greg KH
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