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From: Chris Wilson <chris@chris-wilson.co.uk>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	intel-gfx <intel-gfx@lists.freedesktop.org>,
	Linux-MM <linux-mm@kvack.org>, Pavel Machek <pavel@ucw.cz>,
	Andrew Morton <akpm@linux-foundation.org>,
	Joerg Roedel <jroedel@suse.de>, Dave Airlie <airlied@redhat.com>,
	Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
	Rodrigo Vivi <rodrigo.vivi@intel.com>,
	stable <stable@vger.kernel.org>
Subject: Re: [PATCH 2/4] drm/i915/gem: Sync the vmap PTEs upon construction
Date: Fri, 21 Aug 2020 14:01:41 +0100	[thread overview]
Message-ID: <159801490171.29194.13892566081151243171@build.alporthouse.com> (raw)
In-Reply-To: <CAHk-=wiu1WHD0x0VXKoLQGy43S7KLCY=Yd-TPDh=7tDW08554w@mail.gmail.com>

Quoting Linus Torvalds (2020-08-21 13:41:03)
> On Fri, Aug 21, 2020 at 1:50 AM Chris Wilson <chris@chris-wilson.co.uk> wrote:
> >
> > Since synchronising the PTE after assignment is a manual step, use the
> > newly exported interface to flush the PTE after assigning via
> > alloc_vm_area().
> 
> This commit message doesn't make much sense to me.
> 
> Are you talking about synchronizing the page directory structure
> across processes after possibly creating new kernel page tables?
> 
> Because that has nothing to do with the PTE. It's all about making
> sure the _upper_ layers of the page directories are populated
> everywhere..
> 
> The name seems off to me too - what are you "flushing"? (And yes, I
> know about the flush_cache_vmap(), but that looks just bogus, since
> any non-mapped area shouldn't have any virtual caches to begin with,
> so I suspect that is just the crazy architectures being confused -
> flush_cache_vmap() is a no-op on any sane architecture - and powerpc
> that mis-uses it for other things).

I was trying to mimic map_kernel_range() which does the
arch_sync_kernel_mappings and flush_cache_vmap on top of the
apply_to_page_range performed by alloc_vm_area, because buried away in
there, on x86-32, is a set_pmd(). Since map_kernel_range() wrapped
map_kernel_range_noflush(), flush seemed like the right verb.

Joerg pointed out that the sync belonged to __apply_to_page_range and
fixed it in situ.
-Chris

WARNING: multiple messages have this Message-ID (diff)
From: Chris Wilson <chris@chris-wilson.co.uk>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Joerg Roedel <jroedel@suse.de>,
	intel-gfx <intel-gfx@lists.freedesktop.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	stable <stable@vger.kernel.org>, Linux-MM <linux-mm@kvack.org>,
	Pavel Machek <pavel@ucw.cz>, Dave Airlie <airlied@redhat.com>,
	Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [Intel-gfx] [PATCH 2/4] drm/i915/gem: Sync the vmap PTEs upon construction
Date: Fri, 21 Aug 2020 14:01:41 +0100	[thread overview]
Message-ID: <159801490171.29194.13892566081151243171@build.alporthouse.com> (raw)
In-Reply-To: <CAHk-=wiu1WHD0x0VXKoLQGy43S7KLCY=Yd-TPDh=7tDW08554w@mail.gmail.com>

Quoting Linus Torvalds (2020-08-21 13:41:03)
> On Fri, Aug 21, 2020 at 1:50 AM Chris Wilson <chris@chris-wilson.co.uk> wrote:
> >
> > Since synchronising the PTE after assignment is a manual step, use the
> > newly exported interface to flush the PTE after assigning via
> > alloc_vm_area().
> 
> This commit message doesn't make much sense to me.
> 
> Are you talking about synchronizing the page directory structure
> across processes after possibly creating new kernel page tables?
> 
> Because that has nothing to do with the PTE. It's all about making
> sure the _upper_ layers of the page directories are populated
> everywhere..
> 
> The name seems off to me too - what are you "flushing"? (And yes, I
> know about the flush_cache_vmap(), but that looks just bogus, since
> any non-mapped area shouldn't have any virtual caches to begin with,
> so I suspect that is just the crazy architectures being confused -
> flush_cache_vmap() is a no-op on any sane architecture - and powerpc
> that mis-uses it for other things).

I was trying to mimic map_kernel_range() which does the
arch_sync_kernel_mappings and flush_cache_vmap on top of the
apply_to_page_range performed by alloc_vm_area, because buried away in
there, on x86-32, is a set_pmd(). Since map_kernel_range() wrapped
map_kernel_range_noflush(), flush seemed like the right verb.

Joerg pointed out that the sync belonged to __apply_to_page_range and
fixed it in situ.
-Chris
_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gfx

  reply	other threads:[~2020-08-21 13:01 UTC|newest]

Thread overview: 40+ 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 ` [Intel-gfx] " Chris Wilson
2020-08-21  8:50 ` [PATCH 2/4] drm/i915/gem: Sync the vmap " Chris Wilson
2020-08-21  8:50   ` [Intel-gfx] " Chris Wilson
2020-08-21 12:41   ` Linus Torvalds
2020-08-21 12:41     ` [Intel-gfx] " Linus Torvalds
2020-08-21 12:41     ` Linus Torvalds
2020-08-21 13:01     ` Chris Wilson [this message]
2020-08-21 13:01       ` [Intel-gfx] " 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   ` [Intel-gfx] " 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  8:50   ` [Intel-gfx] " Chris Wilson
2020-08-21  9:14 ` [Intel-gfx] ✗ Fi.CI.CHECKPATCH: warning for series starting with [1/4] mm: Export flush_vm_area() to sync the PTEs upon construction Patchwork
2020-08-21  9:16 ` [Intel-gfx] ✗ Fi.CI.SPARSE: " Patchwork
2020-08-21  9:29 ` [Intel-gfx] ✓ Fi.CI.BAT: success " Patchwork
2020-08-21  9:51 ` [PATCH 1/4] " Joerg Roedel
2020-08-21  9:51   ` [Intel-gfx] " Joerg Roedel
2020-08-21  9:54   ` Chris Wilson
2020-08-21  9:54     ` [Intel-gfx] " Chris Wilson
2020-08-21 10:22     ` Joerg Roedel
2020-08-21 10:22       ` [Intel-gfx] " Joerg Roedel
2020-08-21 10:36       ` Chris Wilson
2020-08-21 10:36         ` [Intel-gfx] " Chris Wilson
2020-08-21 10:09 ` [PATCH] mm: Track page table modifications in __apply_to_page_range() construction Joerg Roedel
2020-08-21 10:09   ` [Intel-gfx] " Joerg Roedel
2020-08-21 10:13   ` Chris Wilson
2020-08-21 10:13     ` [Intel-gfx] " Chris Wilson
2020-08-21 10:23     ` Joerg Roedel
2020-08-21 10:23       ` [Intel-gfx] " Joerg Roedel
2020-08-21 10:39       ` Chris Wilson
2020-08-21 10:39         ` [Intel-gfx] " Chris Wilson
2020-08-21 11:38         ` Chris Wilson
2020-08-21 11:38           ` [Intel-gfx] " Chris Wilson
2020-08-21 12:18           ` Joerg Roedel
2020-08-21 12:18             ` [Intel-gfx] " Joerg Roedel
2020-08-21 10:53   ` Greg KH
2020-08-21 10:53     ` [Intel-gfx] " Greg KH
2020-08-21 10:27 ` [Intel-gfx] ✗ Fi.CI.BUILD: failure for series starting with mm: Track page table modifications in __apply_to_page_range() construction (rev2) Patchwork
2020-08-21 11:33 ` [Intel-gfx] ✓ Fi.CI.IGT: success for series starting with [1/4] mm: Export flush_vm_area() to sync the PTEs upon construction Patchwork

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