FAILED: patch "[PATCH] cxl: Fix number of allocated pages in SPA" failed to apply to 4.2-stable tree

The patch below does not apply to the 4.2-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From: Christophe Lombard <[email protected]>
Date: Wed, 7 Oct 2015 16:07:40 +1100
Subject: [PATCH] cxl: Fix number of allocated pages in SPA

The scheduled process area is currently allocated before assigning the correct maximum processes to the AFU, which will mean we only ever allocate a fixed number of pages for the scheduled process area. This will limit us to 958 processes with 2 x 64K pages. If we try to use more processes than that we'd probably overrun the buffer and corrupt memory or crash.

AFUs that require three or more interrupts per process will not be affected as they are already limited to less processes than that, but we could hit it on an AFU that requires 0, 1 or 2 interrupts per process, or when using 4K pages.

This patch moves the initialisation of the num_procs to before the SPA allocation so that enough pages will be allocated for the number of processes that the AFU supports.

index b37f2e8004f5..d2e75c88f4d2 100644
@@ -457,6 +457,7 @@ static int activate_afu_directed(struct cxl_afu *afu)
 
 	dev_info(&afu->dev, "Activating AFU directed mode\n");
 
+	afu->num_procs = afu->max_procs_virtualised;
 	if (afu->spa == NULL) {
 		if (cxl_alloc_spa(afu))
 			return -ENOMEM;

@@ -468,7 +469,6 @@ static int activate_afu_directed(struct cxl_afu *afu)
 	cxl_p1n_write(afu, CXL_PSL_ID_An, CXL_PSL_ID_An_F | CXL_PSL_ID_An_L);
 
 	afu->current_mode = CXL_MODE_DIRECTED;
-	afu->num_procs = afu->max_procs_virtualised;
 
 	if ((rc = cxl_chardev_m_afu_add(afu)))
 		return rc;