svn commit: r290130 - head/sys/dev/ntb/ntb_hw

[Steven Wahl]

We ran into this exact problem, pmap_change_attr not working right with large bars.  I had been working up to seeing if this compiles on the current head, introducing myself to the community, seeing if this would be accepted.

But looks like it's needed sooner, so in case it might save you some time, here's the patch we developed for this problem.

--> Steve Wahl, Dell Compellent, Eden Prairie, MN


commit 7d112aa8767390cb9dd020325a9f23aaac7fe5a0
Author: swahl <steve_wahl at dell.com>
Date:   Thu Oct 1 14:36:48 2015 -0500

    CQ00492954: FreeBSD traps on call to pmap_change_attr() with large PLX BAR
    
    If an address passed to pmap_change_attr() refers to a virtual address,
    the function must also change the direct mapping of this same
    region (if any) to match, or intel says the result is undefined.
    
    But the original code did not check if the virtual address actually fell
    within the direct mapped region before attempting to make this change.
    The attempt to look up the direct mapped page entries returned NULL, and
    this was dereferenced causing a panic.
    
    This is fixed by checking whether the address is outside of the direct
    mapped range before trying to change the direct mapped entries.

diff --git a/src/sys/amd64/amd64/pmap.c b/src/sys/amd64/amd64/pmap.c
index fe09ace..dee22de 100644
--- a/src/sys/amd64/amd64/pmap.c
+++ b/src/sys/amd64/amd64/pmap.c
@@ -6268,7 +6268,7 @@ pmap_change_attr_locked(vm_offset_t va, vm_size_t size, int mode)
 	 */
 	for (tmpva = base; tmpva < base + size; ) {
 		pdpe = pmap_pdpe(kernel_pmap, tmpva);
-		if (*pdpe == 0)
+		if (pdpe == NULL || *pdpe == 0)
 			return (EINVAL);
 		if (*pdpe & PG_PS) {
 			/*
@@ -6341,7 +6341,8 @@ pmap_change_attr_locked(vm_offset_t va, vm_size_t size, int mode)
 				    X86_PG_PDE_CACHE);
 				changed = TRUE;
 			}
-			if (tmpva >= VM_MIN_KERNEL_ADDRESS) {
+			if (tmpva >= VM_MIN_KERNEL_ADDRESS &&
+			    (*pdpe & PG_PS_FRAME) < dmaplimit) {
 				if (pa_start == pa_end) {
 					/* Start physical address run. */
 					pa_start = *pdpe & PG_PS_FRAME;
@@ -6370,7 +6371,8 @@ pmap_change_attr_locked(vm_offset_t va, vm_size_t size, int mode)
 				    X86_PG_PDE_CACHE);
 				changed = TRUE;
 			}
-			if (tmpva >= VM_MIN_KERNEL_ADDRESS) {
+			if (tmpva >= VM_MIN_KERNEL_ADDRESS &&
+			    (*pde & PG_PS_FRAME) < dmaplimit) {
 				if (pa_start == pa_end) {
 					/* Start physical address run. */
 					pa_start = *pde & PG_PS_FRAME;
@@ -6397,7 +6399,8 @@ pmap_change_attr_locked(vm_offset_t va, vm_size_t size, int mode)
 				    X86_PG_PTE_CACHE);
 				changed = TRUE;
 			}
-			if (tmpva >= VM_MIN_KERNEL_ADDRESS) {
+			if (tmpva >= VM_MIN_KERNEL_ADDRESS &&
+			    (*pte & PG_FRAME) < dmaplimit) {
 				if (pa_start == pa_end) {
 					/* Start physical address run. */
 					pa_start = *pte & PG_FRAME;