From: Michal Hocko <mhocko@kernel.org>
To: "Thomas Hellström (VMware)" <thomas_os@shipmail.org>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
dri-devel@lists.freedesktop.org, pv-drivers@vmware.com,
linux-graphics-maintainer@vmware.com,
"Thomas Hellstrom" <thellstrom@vmware.com>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Matthew Wilcox (Oracle)" <willy@infradead.org>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
"Ralph Campbell" <rcampbell@nvidia.com>,
"Jérôme Glisse" <jglisse@redhat.com>,
"Christian König" <christian.koenig@amd.com>
Subject: Re: [PATCH v2 2/2] drm/ttm: Fix vm page protection handling
Date: Wed, 4 Dec 2019 14:52:19 +0100 [thread overview]
Message-ID: <20191204135219.GH25242@dhcp22.suse.cz> (raw)
In-Reply-To: <20191203104853.4378-3-thomas_os@shipmail.org>
On Tue 03-12-19 11:48:53, Thomas Hellström (VMware) wrote:
> From: Thomas Hellstrom <thellstrom@vmware.com>
>
> TTM graphics buffer objects may, transparently to user-space, move
> between IO and system memory. When that happens, all PTEs pointing to the
> old location are zapped before the move and then faulted in again if
> needed. When that happens, the page protection caching mode- and
> encryption bits may change and be different from those of
> struct vm_area_struct::vm_page_prot.
>
> We were using an ugly hack to set the page protection correctly.
> Fix that and instead use vmf_insert_mixed_prot() and / or
> vmf_insert_pfn_prot().
> Also get the default page protection from
> struct vm_area_struct::vm_page_prot rather than using vm_get_page_prot().
> This way we catch modifications done by the vm system for drivers that
> want write-notification.
So essentially this should have any new side effect on functionality it
is just making a hacky/ugly code less so? In other words what are the
consequences of having page protection inconsistent from vma's?
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
> Cc: Ralph Campbell <rcampbell@nvidia.com>
> Cc: "Jérôme Glisse" <jglisse@redhat.com>
> Cc: "Christian König" <christian.koenig@amd.com>
> Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
> Reviewed-by: Christian König <christian.koenig@amd.com>
> ---
> drivers/gpu/drm/ttm/ttm_bo_vm.c | 14 +++++++-------
> 1 file changed, 7 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c b/drivers/gpu/drm/ttm/ttm_bo_vm.c
> index e6495ca2630b..2098f8d4dfc5 100644
> --- a/drivers/gpu/drm/ttm/ttm_bo_vm.c
> +++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c
> @@ -173,7 +173,6 @@ vm_fault_t ttm_bo_vm_fault_reserved(struct vm_fault *vmf,
> pgoff_t num_prefault)
> {
> struct vm_area_struct *vma = vmf->vma;
> - struct vm_area_struct cvma = *vma;
> struct ttm_buffer_object *bo = vma->vm_private_data;
> struct ttm_bo_device *bdev = bo->bdev;
> unsigned long page_offset;
> @@ -244,7 +243,7 @@ vm_fault_t ttm_bo_vm_fault_reserved(struct vm_fault *vmf,
> goto out_io_unlock;
> }
>
> - cvma.vm_page_prot = ttm_io_prot(bo->mem.placement, prot);
> + prot = ttm_io_prot(bo->mem.placement, prot);
> if (!bo->mem.bus.is_iomem) {
> struct ttm_operation_ctx ctx = {
> .interruptible = false,
> @@ -260,7 +259,7 @@ vm_fault_t ttm_bo_vm_fault_reserved(struct vm_fault *vmf,
> }
> } else {
> /* Iomem should not be marked encrypted */
> - cvma.vm_page_prot = pgprot_decrypted(cvma.vm_page_prot);
> + prot = pgprot_decrypted(prot);
> }
>
> /*
> @@ -284,10 +283,11 @@ vm_fault_t ttm_bo_vm_fault_reserved(struct vm_fault *vmf,
> }
>
> if (vma->vm_flags & VM_MIXEDMAP)
> - ret = vmf_insert_mixed(&cvma, address,
> - __pfn_to_pfn_t(pfn, PFN_DEV));
> + ret = vmf_insert_mixed_prot(vma, address,
> + __pfn_to_pfn_t(pfn, PFN_DEV),
> + prot);
> else
> - ret = vmf_insert_pfn(&cvma, address, pfn);
> + ret = vmf_insert_pfn_prot(vma, address, pfn, prot);
>
> /* Never error on prefaulted PTEs */
> if (unlikely((ret & VM_FAULT_ERROR))) {
> @@ -319,7 +319,7 @@ vm_fault_t ttm_bo_vm_fault(struct vm_fault *vmf)
> if (ret)
> return ret;
>
> - prot = vm_get_page_prot(vma->vm_flags);
> + prot = vma->vm_page_prot;
> ret = ttm_bo_vm_fault_reserved(vmf, prot, TTM_BO_VM_NUM_PREFAULT);
> if (ret == VM_FAULT_RETRY && !(vmf->flags & FAULT_FLAG_RETRY_NOWAIT))
> return ret;
> --
> 2.21.0
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2019-12-04 13:52 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-03 10:48 [PATCH v2 0/2] mm, drm/ttm: Fix pte insertion with customized protection Thomas Hellström (VMware)
2019-12-03 10:48 ` [PATCH v2 1/2] mm: Add and export vmf_insert_mixed_prot() Thomas Hellström (VMware)
2019-12-04 13:48 ` Michal Hocko
2019-12-03 10:48 ` [PATCH v2 2/2] drm/ttm: Fix vm page protection handling Thomas Hellström (VMware)
2019-12-04 13:52 ` Michal Hocko [this message]
2019-12-04 14:16 ` Thomas Hellström (VMware)
2019-12-04 14:35 ` Michal Hocko
2019-12-04 14:36 ` Thomas Hellström (VMware)
2019-12-04 14:42 ` Michal Hocko
2019-12-04 15:19 ` Thomas Hellström (VMware)
2019-12-04 15:26 ` Michal Hocko
2019-12-04 15:29 ` Thomas Hellström (VMware)
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20191204135219.GH25242@dhcp22.suse.cz \
--to=mhocko@kernel.org \
--cc=akpm@linux-foundation.org \
--cc=christian.koenig@amd.com \
--cc=dri-devel@lists.freedesktop.org \
--cc=jglisse@redhat.com \
--cc=kirill.shutemov@linux.intel.com \
--cc=linux-graphics-maintainer@vmware.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=pv-drivers@vmware.com \
--cc=rcampbell@nvidia.com \
--cc=thellstrom@vmware.com \
--cc=thomas_os@shipmail.org \
--cc=willy@infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).