amd64/133592: busdma incorrectly calculates bounce buffer requirements for userspace buffers

[Jason Harmening]

>Number:         133592
>Category:       amd64
>Synopsis:       busdma incorrectly calculates bounce buffer requirements for userspace buffers
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    freebsd-amd64
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Sat Apr 11 02:40:00 UTC 2009
>Closed-Date:
>Last-Modified:
>Originator:     Jason Harmening
>Release:        7.2-PRERELEASE
>Organization:
>Environment:
FreeBSD CORONA 7.2-PRERELEASE FreeBSD 7.2-PRERELEASE #2: Sat Mar 21 00:30:34 CDT 2009     jason at CORONA:/usr/obj/usr/src/sys/CUSTOM  amd64

>Description:
The _bus_dmamap_load_buffer function in sys/amd64/amd64/busdma_machdep.c takes a pmap_t param indicating the address space of the buffer (NULL => KVA space).  When calculating the number of bounce buffers to reserve, it always calls pmap_kextract() to get the physical address, when it should call pmap_extract() if pmap != NULL.

The problem exists in both 7-STABLE and 8-CURRENT--the attached patch is against 7-STABLE.
>How-To-Repeat:

>Fix:


Patch attached with submission follows:

--- busdma_machdep.c.bkp	2009-04-10 21:27:51.000000000 -0500
+++ busdma_machdep.c	2009-04-10 21:30:58.000000000 -0500
@@ -602,7 +602,10 @@
 		vendaddr = (vm_offset_t)buf + buflen;
 
 		while (vaddr < vendaddr) {
-			paddr = pmap_kextract(vaddr);
+			if (pmap)
+				paddr = pmap_extract(pmap, vaddr);
+			else
+				paddr = pmap_kextract(vaddr);
 			if (run_filter(dmat, paddr) != 0)
 				map->pagesneeded++;
 			vaddr += PAGE_SIZE;


>Release-Note:
>Audit-Trail:
>Unformatted: