Re: [PATCH v5 0/6] hw/cxl: Poison get, inject, clear

[Jonathan Cameron]

On Fri, 19 May 2023 04:49:46 -0400
"Michael S. Tsirkin" <mst@redhat.com> wrote:

> On Sun, Apr 23, 2023 at 05:20:07PM +0100, Jonathan Cameron wrote:
> > v5: More details in each patch.
> >  - Simpler algorithm to find entry when clearing.
> >  - Improvements to debugability and docs for 24 bit endian functions.
> >  - Use of ROUND_DOWN() to simplify the various alignment questions.
> >  - Use CXL_CACHELINE_SIZE define to explain the mysterious 64 byte
> >    granularity
> >  - Use memory_region_size() instead of direct accesses.  
> 
> 
> picked first 3 but dropped the rest for now due to build errors.
Drop the bswap one as well for now.
s390 is trying to call __builtin_bswap24 which clearly doesn't exist
- though you won't see that without the rest of this patch set.

Might be a case of crossing with a patch set reworking this stuff
to use the compiler more, but I'm not quite sure.

I'll see if I can figure out a fix or indeed exactly how this is
being triggered.

Hindsight says we should have kept definition local to CXL and
done the 'generic' version afterwards. 

For reference

/builds/jic23/qemu/include/qemu/bswap.h:42:32: error: implicit declaration of 
function ‘__builtin_bswap24’; did you mean ‘__builtin_bswap64’? 
[-Werror=implicit-function-declaration]
   42 | #define le_bswap(v, size) glue(__builtin_bswap, size)(v)
      |                                ^~~~~~~~~~~~~~~
/builds/jic23/qemu/include/qemu/compiler.h:34:21: note: in definition of macro 
‘xglue’
   34 | #define xglue(x, y) x ## y
      |                     ^
/builds/jic23/qemu/include/qemu/bswap.h:42:27: note: in expansion of macro 
‘glue’
   42 | #define le_bswap(v, size) glue(__builtin_bswap, size)(v)
      |                           ^~~~
/builds/jic23/qemu/include/qemu/bswap.h:322:20: note: in expansion of macro 
‘le_bswap’
  322 |     st24_he_p(ptr, le_bswap(v, 24));
      |                    ^~~~~~~~
/builds/jic23/qemu/include/qemu/bswap.h:42:32: error: nested extern declaration 
of ‘__builtin_bswap24’ [-Werror=nested-externs]
   42 | #define le_bswap(v, size) glue(__builtin_bswap, size)(v)
      |                                ^~~~~~~~~~~~~~~
/builds/jic23/qemu/include/qemu/compiler.h:34:21: note: in definition of macro 
‘xglue’
   34 | #define xglue(x, y) x ## y
      |                     ^
/builds/jic23/qemu/include/qemu/bswap.h:42:27: note: in expansion of macro 
‘glue’
   42 | #define le_bswap(v, size) glue(__builtin_bswap, size)(v)
      |                           ^~~~
/builds/jic23/qemu/include/qemu/bswap.h:322:20: note: in expansion of macro 
‘le_bswap’
  322 |     st24_he_p(ptr, le_bswap(v, 24));
      |                    ^~~~~~~~

Jonathan
 
> 
> > Many of the precursors listed for v4 have now been applied, but
> > a few minor fixes have come up in the meantime so there are still
> > a few precursors including the volatile support left from v4
> > precursors.
> > 
> > Depends on 
> > [PATCH 0/2] hw/cxl: CDAT file handling fixes.
> > [PATCH v2 0/3] hw/cxl: Fix decoder commit and uncommit handling
> > [PATCH 0/3] docs/cxl: Gathering of fixes for 8.0 CXL docs.
> > [PATCH v5 0/3] hw/mem: CXL Type-3 Volatile Memory Support
> >  
> > Based on: Message-ID: 20230421132020.7408-1-Jonathan.Cameron@huawei.com
> > Based on: Message-ID: 20230421135906.3515-1-Jonathan.Cameron@huawei.com
> > Based on: Message-ID: 20230421134507.26842-1-Jonathan.Cameron@huawei.com
> > Based on: Message-ID: 20230421160827.2227-1-Jonathan.Cameron@huawei.com
> > 
> > The kernel support for Poison handling is currently in the cxl/pending
> > branch and hopefully should be in the CXL pull request next week.
> > 
> > https://git.kernel.org/pub/scm/linux/kernel/git/cxl/cxl.git/log/?h=pending
> > 
> > This code has been very useful for testing and helped identify various
> > corner cases.
> > 
> > Updated cover letter.
> > 
> > The series supports:
> > 1) Injection of variable length poison regions via QMP (to fake real
> >    memory corruption and ensure we deal with odd overflow corner cases
> >    such as clearing the middle of a large region making the list overflow
> >    as we go from one long entry to two smaller entries.
> > 2) Read of poison list via the CXL mailbox.
> > 3) Injection via the poison injection mailbox command (limited to 64 byte
> >    entries - spec constraint)
> > 4) Clearing of poison injected via either method.
> > 
> > The implementation is meant to be a valid combination of impdef choices
> > based on what the spec allowed. There are a number of places where it could
> > be made more sophisticated that we might consider in future:
> > * Fusing adjacent poison entries if the types match.
> > * Separate injection list and main poison list, to test out limits on
> >   injected poison list being smaller than the main list.
> > * Poison list overflow event (needs event log support in general)
> > * Connecting up to the poison list error record generation (rather complex
> >   and not needed for currently kernel handling testing).
> > * Triggering the synchronous and asynchronous errors that occur on reads
> >   and writes of the memory when the host receives poison.
> > 
> > As the kernel code is currently fairly simple, it is likely that the above
> > does not yet matter but who knows what will turn up in future!
> > 
> > 
> > Ira Weiny (2):
> >   hw/cxl: Introduce cxl_device_get_timestamp() utility function
> >   bswap: Add the ability to store to an unaligned 24 bit field
> > 
> > Jonathan Cameron (4):
> >   hw/cxl: rename mailbox return code type from ret_code to CXLRetCode
> >   hw/cxl: QMP based poison injection support
> >   hw/cxl: Add poison injection via the mailbox.
> >   hw/cxl: Add clear poison mailbox command support.
> > 
> >  docs/devel/loads-stores.rst |   1 +
> >  hw/cxl/cxl-device-utils.c   |  15 ++
> >  hw/cxl/cxl-mailbox-utils.c  | 289 ++++++++++++++++++++++++++++++------
> >  hw/mem/cxl_type3.c          |  93 ++++++++++++
> >  hw/mem/cxl_type3_stubs.c    |   6 +
> >  include/hw/cxl/cxl.h        |   1 +
> >  include/hw/cxl/cxl_device.h |  23 +++
> >  include/qemu/bswap.h        |  25 ++++
> >  qapi/cxl.json               |  18 +++
> >  9 files changed, 429 insertions(+), 42 deletions(-)
> > 
> > -- 
> > 2.37.2  
>