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Re: port-amd64/42980: satalink DMA fails under amd64



On Fri, Mar 19, 2010 at 04:41:16PM +0100, Manuel Bouyer wrote:
> On Fri, Mar 19, 2010 at 09:47:39AM -0400, Julian Bourne wrote:
> > I applied the patch to 5.0.2 (hope that was right - it
> > applied cleanly) and rebuilt my xen dom0 target.
> > 
> > It hit a __kern_assert() in uvm_pglistalloc():403
> > called from xen_bus_dmamem_alloc_range():
> > 
> > (boundary & (boundary - 1) == 0) failed
> 
> that's strange, because in xen_bus_dmamem_alloc_range() this could be either
> boundary (and this check is already done in xen_bus_dmamem_alloc_range())
> or size (which is rounded to PAGE_SIZE). Could you print the
> values for boundary and size here ?

ignore this, rounding up to PAGE_SIZE is not enough to make it a power of 2.

The attached patch should be correct (at last I hope so, it's becoming more
complex than I'd like ...)

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--
Index: x86/x86/bus_dma.c
===================================================================
RCS file: /cvsroot/src/sys/arch/x86/x86/bus_dma.c,v
retrieving revision 1.45
diff -u -p -u -r1.45 bus_dma.c
--- x86/x86/bus_dma.c   28 Jun 2008 17:23:01 -0000      1.45
+++ x86/x86/bus_dma.c   19 Mar 2010 16:05:28 -0000
@@ -155,14 +155,28 @@ _bus_dmamem_alloc_range(bus_dma_tag_t t,
        struct vm_page *m;
        struct pglist mlist;
        int curseg, error;
+       bus_size_t uboundary;
 
        /* Always round the size. */
        size = round_page(size);
 
+       KASSERT(boundary >= PAGE_SIZE || boundary == 0);
+
        /*
         * Allocate pages from the VM system.
-        */
-       error = uvm_pglistalloc(size, low, high, alignment, boundary,
+        * We accept boundaries < size, splitting in multiple segments
+        * if needed. uvm_pglistalloc does not, so compute an appropriate
+         * boundary: next power of 2 >= size
+         */
+
+       if (boundary == 0)
+               uboundary = 0;
+       else {
+               uboundary = boundary;
+               while (uboundary < size)
+                       uboundary = uboundary << 1;
+       }
+       error = uvm_pglistalloc(size, low, high, alignment, uboundary,
            &mlist, nsegs, (flags & BUS_DMA_NOWAIT) == 0);
        if (error)
                return (error);
@@ -186,10 +200,13 @@ _bus_dmamem_alloc_range(bus_dma_tag_t t,
                        panic("_bus_dmamem_alloc_range");
                }
 #endif
-               if (curaddr == (lastaddr + PAGE_SIZE))
+               if (curaddr == (lastaddr + PAGE_SIZE) &&
+                   (lastaddr & boundary) == (curaddr & boundary)) {
                        segs[curseg].ds_len += PAGE_SIZE;
-               else {
+               } else {
                        curseg++;
+                       if (curseg >= nsegs)
+                               return EFBIG;
                        segs[curseg].ds_addr = curaddr;
                        segs[curseg].ds_len = PAGE_SIZE;
                }
Index: xen/x86/xen_bus_dma.c
===================================================================
RCS file: /cvsroot/src/sys/arch/xen/x86/xen_bus_dma.c,v
retrieving revision 1.11.8.1
diff -u -p -u -r1.11.8.1 xen_bus_dma.c
--- xen/x86/xen_bus_dma.c       30 Jan 2010 19:14:20 -0000      1.11.8.1
+++ xen/x86/xen_bus_dma.c       19 Mar 2010 16:05:28 -0000
@@ -61,7 +61,7 @@ static inline int get_order(unsigned lon
 }
 
 static int
-_xen_alloc_contig(bus_size_t size, bus_size_t alignment, bus_size_t boundary,
+_xen_alloc_contig(bus_size_t size, bus_size_t alignment,
     struct pglist *mlistp, int flags, bus_addr_t low, bus_addr_t high)
 {
        int order, i;
@@ -75,9 +75,9 @@ _xen_alloc_contig(bus_size_t size, bus_s
 
        /*
         * When requesting a contigous memory region, the hypervisor will
-        * return a memory range aligned on size. This will automagically
-        * handle "boundary", but the only way to enforce alignment
-        * is to request a memory region of size max(alignment, size).
+        * return a memory range aligned on size. 
+        * The only way to enforce alignment is to request a memory region
+        * of size max(alignment, size).
         */
        order = max(get_order(size), get_order(alignment));
        npages = (1 << order);
@@ -244,21 +244,32 @@ _xen_bus_dmamem_alloc_range(bus_dma_tag_
        struct pglist mlist;
        int curseg, error;
        int doingrealloc = 0;
+       bus_size_t uboundary;
 
        /* Always round the size. */
        size = round_page(size);
 
        KASSERT((alignment & (alignment - 1)) == 0);
        KASSERT((boundary & (boundary - 1)) == 0);
+       KASSERT(boundary >= PAGE_SIZE || boundary == 0);
+                   
        if (alignment < PAGE_SIZE)
                alignment = PAGE_SIZE;
-       if (boundary != 0 && boundary < size)
-               return (EINVAL);
 
        /*
         * Allocate pages from the VM system.
+        * We accept boundaries < size, splitting in multiple segments
+        * if needed. uvm_pglistalloc does not, so compute an appropriate
+        * boundary: next power of 2 >= size
         */
-       error = uvm_pglistalloc(size, 0, avail_end, alignment, boundary,
+       if (boundary == 0)
+               uboundary = 0;
+       else {
+               uboundary = boundary;
+               while (uboundary < size)
+                       uboundary = uboundary << 1;
+       }
+       error = uvm_pglistalloc(size, 0, avail_end, alignment, uboundary,
            &mlist, nsegs, (flags & BUS_DMA_NOWAIT) == 0);
        if (error)
                return (error);
@@ -282,14 +293,18 @@ again:
                curaddr = _BUS_VM_PAGE_TO_BUS(m);
                if (curaddr < low || curaddr >= high)
                        goto badaddr;
-               if (curaddr == (lastaddr + PAGE_SIZE)) {
+               if (curaddr == (lastaddr + PAGE_SIZE) &&
+                   (lastaddr & boundary) == (curaddr & boundary)) {
                        segs[curseg].ds_len += PAGE_SIZE;
-                       if ((lastaddr & boundary) != (curaddr & boundary))
-                               goto dorealloc;
                } else {
                        curseg++;
-                       if (curseg >= nsegs || (curaddr & (alignment - 1)) != 0)
-                               goto dorealloc;
+                       if (curseg >= nsegs ||
+                           (curaddr & (alignment - 1)) != 0) {
+                               if (doingrealloc)
+                                       return EFBIG;
+                               else
+                                       goto dorealloc;
+                       }
                        segs[curseg].ds_addr = curaddr;
                        segs[curseg].ds_len = PAGE_SIZE;
                }
@@ -343,7 +358,7 @@ dorealloc:
                segs[curseg].ds_len = 0;
        }
        error = _xen_alloc_contig(size, alignment,
-           boundary, &mlist, flags, low, high);
+           &mlist, flags, low, high);
        if (error)
                return error;
        goto again;


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