linux-toradex.git/include/xen/grant_table.h, branch v4.4.58

xen/grant-table: Add an helper to iterate over a specific number of grants

2015-10-23T13:20:46+00:00

With the 64KB page granularity support on ARM64, a Linux page may be
split accross multiple grant.

Currently we have the helper gnttab_foreach_grant_in_grant to break a
Linux page based on an offset and a len, but it doesn't fit when we only
have a number of grants in hand.

Introduce a new helper which take an array of Linux page and a number of
grant and will figure out the address of each grant.

Signed-off-by: Julien Grall 
Signed-off-by: David Vrabel

xen/grant: Add helper gnttab_page_grant_foreign_access_ref_one

2015-10-23T13:20:34+00:00

Many PV drivers contain the idiom:

pfn = page_to_gfn(...) /* Or similar */
gnttab_grant_foreign_access_ref

Replace it by a new helper. Note that when Linux is using a different
page granularity than Xen, the helper only gives access to the first 4KB
grant.

This is useful where drivers are allocating a full Linux page for each
grant.

Also include xen/interface/grant_table.h rather than xen/grant_table.h in
asm/page.h for x86 to fix a compilation issue [1]. Only the former is
useful in order to get the structure definition.

[1] Interdependency between asm/page.h and xen/grant_table.h which result
to page_mfn not being defined when necessary.

Signed-off-by: Julien Grall 
Reviewed-by: David Vrabel 
Reviewed-by: Stefano Stabellini 
Signed-off-by: David Vrabel

xen/grant: Introduce helpers to split a page into grant

2015-10-23T13:20:33+00:00

Currently, a grant is always based on the Xen page granularity (i.e
4KB). When Linux is using a different page granularity, a single page
will be split between multiple grants.

The new helpers will be in charge of splitting the Linux page into grants
and call a function given by the caller on each grant.

Also provide an helper to count the number of grants within a given
contiguous region.

Note that the x86/include/asm/xen/page.h is now including
xen/interface/grant_table.h rather than xen/grant_table.h. It's
necessary because xen/grant_table.h depends on asm/xen/page.h and will
break the compilation. Furthermore, only definition in
interface/grant_table.h is required.

Signed-off-by: Julien Grall 
Reviewed-by: David Vrabel 
Reviewed-by: Stefano Stabellini 
Signed-off-by: David Vrabel

xen/grant: introduce func gnttab_unmap_refs_sync()

2015-04-27T10:41:12+00:00

There are several place using gnttab async unmap and wait for
completion, so move the common code to a function
gnttab_unmap_refs_sync().

Signed-off-by: Bob Liu 
Acked-by: Roger Pau Monné 
Acked-by: Konrad Rzeszutek Wilk 
Signed-off-by: David Vrabel

xen/grant-table: add a mechanism to safely unmap pages that are in use

2015-01-28T14:03:14+00:00

Introduce gnttab_unmap_refs_async() that can be used to safely unmap
pages that may be in use (ref count > 1).  If the pages are in use the
unmap is deferred and retried later.  This polling is not very clever
but it should be good enough if the cases where the delay is necessary
are rare.

The initial delay is 5 ms and is increased linearly on each subsequent
retry (to reduce load if the page is in use for a long time).

This is needed to allow block backends using grant mapping to safely
use network storage (block or filesystem based such as iSCSI or NFS).

The network storage driver may complete a block request whilst there
is a queued network packet retry (because the ack from the remote end
races with deciding to queue the retry).  The pages for the retried
packet would be grant unmapped and the network driver (or hardware)
would access the unmapped page.

Signed-off-by: Jennifer Herbert 
Acked-by: Stefano Stabellini 
Signed-off-by: David Vrabel

xen: mark grant mapped pages as foreign

2015-01-28T14:03:12+00:00

Use the "foreign" page flag to mark pages that have a grant map.  Use
page->private to store information of the grant (the granting domain
and the grant reference).

Signed-off-by: Jennifer Herbert 
Reviewed-by: Stefano Stabellini 
Signed-off-by: David Vrabel

xen/grant-table: add helpers for allocating pages

2015-01-28T14:03:12+00:00

Add gnttab_alloc_pages() and gnttab_free_pages() to allocate/free pages
suitable to for granted maps.

Signed-off-by: David Vrabel 
Reviewed-by: Stefano Stabellini

xen/grant-table: pre-populate kernel unmap ops for xen_gnttab_unmap_refs()

2015-01-28T14:03:10+00:00

When unmapping grants, instead of converting the kernel map ops to
unmap ops on the fly, pre-populate the set of unmap ops.

This allows the grant unmap for the kernel mappings to be trivially
batched in the future.

Signed-off-by: David Vrabel 
Reviewed-by: Stefano Stabellini

xen/grant-table: remove support for V2 tables

2014-07-14T19:28:30+00:00

Since 11c7ff17c9b6dbf3a4e4f36be30ad531a6cf0ec9 (xen/grant-table: Force
to use v1 of grants.) the code for V2 grant tables is not used.

Signed-off-by: David Vrabel 
Signed-off-by: Konrad Rzeszutek Wilk

x86/xen: safely map and unmap grant frames when in atomic context

2014-07-14T19:28:02+00:00

arch_gnttab_map_frames() and arch_gnttab_unmap_frames() are called in
atomic context but were calling alloc_vm_area() which might sleep.

Also, if a driver attempts to allocate a grant ref from an interrupt
and the table needs expanding, then the CPU may already by in lazy MMU
mode and apply_to_page_range() will BUG when it tries to re-enable
lazy MMU mode.

These two functions are only used in PV guests.

Introduce arch_gnttab_init() to allocates the virtual address space in
advance.

Avoid the use of apply_to_page_range() by using saving and using the
array of PTE addresses from the alloc_vm_area() call.

N.B. 'alloc_vm_area' pre-allocates the pagetable so there is no need
to worry about having to do a PGD/PUD/PMD walk (like apply_to_page_range
does) and we can instead do set_pte.

Signed-off-by: David Vrabel 
Signed-off-by: Konrad Rzeszutek Wilk 
----
[v2: Add comment about alloc_vm_area]
[v3: Fix compile error found by 0-day bot]