[Xen-devel] [PATCH v9 0/8] xen/arm: introduce GNTTABOP_cache_flush

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

Hi all,
this patch series introduces a new hypercall to perform cache
maintenance operations on behalf of the guest. It is useful for dom0 to
be able to cache flush pages involved in a dma operation with
non-coherent devices.

It also removes XENFEAT_grant_map_identity as the feature is no longer
necessary: it was used to achieve the same goal but the guest can now
use the hypercall instead. Keeping the flag would also have a
significant performance impact as a new p2m mapping gets created and
then destroyed for every grant that is mapped and unmapped in dom0.



Changes in v9:
- fix coding style for comments;
- other style fixes;
- fix whitespace indentation;
- remove useless ASSERT;
- add a comment on ARM callers assuming that these functions cannot
fail;
- grant_map_exists: calculate max iteration before the loop;
- do_grant_table_op: avoid shifts, use masks instead;
- set GNTTABOP_CONTINUATION_ARG_SHIFT to 12;
- remove MAX_GRANT_ENTRIES_ITER_SHIFT, use
GNTTABOP_CONTINUATION_ARG_SHIFT;
- move GNTTABOP_CMD_MASK and GNTTABOP_CONTINUATION_ARG_SHIFT to
grant_table.c.

Changes in v8:
- remove unused #include;
- set max_nr_grant_frames as __initdata;
- set max_grant_frames and max_maptrack_frames as __read_mostly;
- respent coding style for comments;
- remove MAX_MAPTRACK_TO_GRANTS_RATIO;
- avoid security issues, use two separate opaque variables to store the
input argument and the output argument;
- fix return values of grant_map_exists;
- rename CMD_MASK to GNTTABOP_CMD_MASK;
- rename OPAQUE_CONTINUATION_ARG_SHIFT to
GNTTABOP_CONTINUATION_ARG_SHIFT;
- save in the opaque argument the shifted ref_count;
- set GNTTABOP_CONTINUATION_ARG_SHIFT to 20 and
MAX_GRANT_ENTRIES_ITER_SHIFT to 12, to cover the full grant_ref_t value
range;
- move GNTTABOP_CONTINUATION_ARG_SHIFT and GNTTABOP_CMD_MASK to
include/xen/grant_table.h;
- cmd &= GNTTABOP_CMD_MASK in the compat wrapper.

Changes in v7:
- remove 0 initializers;
- make max_nr_grant_frames static;
- remove preprocessors check on max_nr_grant_frames;
- remove double black line;
- introduce DEFAULT_MAX_MAPTRACK_FRAMES;
- no long lines;
- set the new variables independently if the old one is passed as
argument;
- return the called function's return value from clean_dcache_va_range;
- remove warning message;
- prefix second line of the warning with XENLOG_WARNING;
- do not lower DEFAULT_MAX_NR_GRANT_FRAMES;
- no long lines;
- interrupt loops in grant_map_exists with more than 2048 iterations,
  create an hypercall continuation if necessary.

Changes in v6:
- change ordering of new options in xen-command-line.markdown;
- initialize all options to 0, then set the defaults on an initcall
depending on what options are used;
- do not return int from flush_page_to_ram;
- set DEFAULT_MAX_NR_GRANT_FRAMES to 10;
- warn if max_grant_frames > 10.

Changes in v5:
- /max_nr_maptrack_frames/max_maptrack_frames/g;
- deprecate gnttab_max_nr_frames;
- introduce gnttab_max_frames;
- rename the max_nr_grant_frames variable to max_grant_frames;
- return int from flush_page_to_ram and *_dcache_va_range;
- return int from invalidate_dcache_va_range;
- make order an unsigned int;
- add a comment on sub-page granularity support;
- cache operations return error;
- move the functions to xen/include/asm-x86/flushtlb.h;
- make mfn unsigned long;
- remove unhelpful error message;
- handle errors returned by cache maintenance functions.

Changes in v4:
- add patch "xen: introduce gnttab_max_nr_maptrack_frames command line option";
- remove patch "introduce two different max_nr_dom0/domU_grant_frames
parameters";
- rename *_xen_dcache_* operations to *_dcache_*;
- implement the x86 cache maintenance functions using flush_area_local;
- ASSERT(spin_is_locked);
- return instead of break in grant_map_exists;
- pass a pointer to __gnttab_cache_flush;
- code style;
- unsigned int iterator in gnttab_cache_flush;
- return ret instead -ret;
- cflush.offset >= PAGE_SIZE return -EINVAL;
- revert "xen: introduce arch_grant_(un)map_page_identity"

Changes in v3:
- introduce two different  max_nr_dom0/domU_grant_frames parameters;
- x86: introduce more cache maintenance operations;
- reduce the time the grant_table lock is held;
- fix warning message;
- s/EFAULT/EPERM;
- s/llx/PRIx64;
- check offset and size independetly before checking their sum;
- rcu_lock_current_domain cannot fail;
- s/ENOSYS/EOPNOTSUPP;
- use clean_and_invalidate_xen_dcache_va_range to do both operations at
once;
- fold grant_map_exists in this patch;
- support "count" argument;
- make correspondent changes to compat/grant_table.c;
- introduce GNTTAB_CACHE_SOURCE_GREF to select the type of input in the
union;
- rename size field to length;
- make length and offset uint16_t;
- only take spin_lock if d != owner.

Changes in v2:
- make grant_map_exists static;
- remove the spin_lock in grant_map_exists;
- move the hypercall to GNTTABOP;
- do not check for mfn_to_page errors in GNTTABOP_cache_flush;
- take a reference to the page in GNTTABOP_cache_flush;
- replace printk with gdprintk in GNTTABOP_cache_flush;
- split long line in GNTTABOP_cache_flush;
- remove out label in GNTTABOP_cache_flush;
- move rcu_lock_current_domain down before the loop in
GNTTABOP_cache_flush;
- take a spin_lock before calling grant_map_exists in
GNTTABOP_cache_flush.



Stefano Stabellini (8):
      xen: introduce gnttab_max_frames and gnttab_max_maptrack_frames command 
line options
      xen/arm: rename *_xen_dcache_* operations to *_dcache_*
      xen/arm: return int from *_dcache_va_range
      xen/arm: introduce invalidate_dcache_va_range
      xen/x86: introduce more cache maintenance operations
      xen/arm: introduce GNTTABOP_cache_flush
      Revert "xen/arm: introduce XENFEAT_grant_map_identity"
      Revert "xen: introduce arch_grant_(un)map_page_identity"

 docs/misc/xen-command-line.markdown |   17 ++-
 xen/arch/arm/domain.c               |    2 +-
 xen/arch/arm/guestcopy.c            |    2 +-
 xen/arch/arm/kernel.c               |    2 +-
 xen/arch/arm/mm.c                   |   26 ++--
 xen/arch/arm/p2m.c                  |   30 +---
 xen/arch/arm/smpboot.c              |    2 +-
 xen/arch/x86/mm.c                   |    2 +-
 xen/common/compat/grant_table.c     |   27 ++--
 xen/common/grant_table.c            |  260 ++++++++++++++++++++++++++++-------
 xen/common/kernel.c                 |    2 -
 xen/drivers/passthrough/arm/smmu.c  |   42 ++++++
 xen/include/asm-arm/arm32/page.h    |    7 +-
 xen/include/asm-arm/arm64/page.h    |    7 +-
 xen/include/asm-arm/grant_table.h   |    5 +-
 xen/include/asm-arm/p2m.h           |    4 -
 xen/include/asm-arm/page.h          |   56 ++++++--
 xen/include/asm-x86/flushtlb.h      |   15 ++
 xen/include/asm-x86/p2m.h           |    4 -
 xen/include/asm-x86/page.h          |    3 -
 xen/include/public/features.h       |    4 +-
 xen/include/public/grant_table.h    |   21 +++
 xen/include/xen/grant_table.h       |    4 +-
 xen/include/xlat.lst                |    1 +
 24 files changed, 409 insertions(+), 136 deletions(-)

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