From: Vaibhav Jain vaibhav@linux.ibm.com

On Power-8 the AFU attr prefault_mode tried to improve storage fault performance by prefaulting process segments. However Power-9 radix mode doesn't have Storage-Segments and prefaulting Pages is too fine grained.

So this patch updates prefault_mode_store() to not allow any other value apart from CXL_PREFAULT_NONE when radix mode is enabled.

Cc: stable@vger.kernel.org Fixes: f24be42aab37 ("cxl: Add psl9 specific code") Signed-off-by: Vaibhav Jain vaibhav@linux.ibm.com --- Documentation/ABI/testing/sysfs-class-cxl | 4 +++- drivers/misc/cxl/sysfs.c | 16 ++++++++++++---- 2 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/Documentation/ABI/testing/sysfs-class-cxl b/Documentation/ABI/testing/sysfs-class-cxl index 640f65e79ef1..267920a1874b 100644 --- a/Documentation/ABI/testing/sysfs-class-cxl +++ b/Documentation/ABI/testing/sysfs-class-cxl @@ -69,7 +69,9 @@ Date: September 2014 Contact: linuxppc-dev@lists.ozlabs.org Description: read/write Set the mode for prefaulting in segments into the segment table - when performing the START_WORK ioctl. Possible values: + when performing the START_WORK ioctl. Only applicable when + running under hashed page table mmu. + Possible values: none: No prefaulting (default) work_element_descriptor: Treat the work element descriptor as an effective address and diff --git a/drivers/misc/cxl/sysfs.c b/drivers/misc/cxl/sysfs.c index 4b5a4c5d3c01..629e2e156412 100644 --- a/drivers/misc/cxl/sysfs.c +++ b/drivers/misc/cxl/sysfs.c @@ -353,12 +353,20 @@ static ssize_t prefault_mode_store(struct device *device, struct cxl_afu *afu = to_cxl_afu(device); enum prefault_modes mode = -1;

- if (!strncmp(buf, "work_element_descriptor", 23)) - mode = CXL_PREFAULT_WED; - if (!strncmp(buf, "all", 3)) - mode = CXL_PREFAULT_ALL; if (!strncmp(buf, "none", 4)) mode = CXL_PREFAULT_NONE; + else { + if (!radix_enabled()) { + + /* only allowed when not in radix mode */ + if (!strncmp(buf, "work_element_descriptor", 23)) + mode = CXL_PREFAULT_WED; + if (!strncmp(buf, "all", 3)) + mode = CXL_PREFAULT_ALL; + } else { + dev_err(device, "Cannot prefault with radix enabled\n"); + } + }

if (mode == -1) return -EINVAL;