| Message ID | 20210329121408.17862-2-FelixCui-oc@zhaoxin.com |
|---|---|
| State | New |
| Headers | show |
| Series | Remove flatview_simplify() | expand |
On 3/29/21 6:14 AM, FelixCuioc wrote: > Flatview_simplify() can merge many small memory ranges > into a large one and contains EHCI dma buffers. > For example,the merged range maybe0xc0000-0xbfffffff. > When seabios write PAM register to change the properties > of part of the merged range from RW to readonly, > this action cause the merged IOVA mapping will be > unmapped.But EHCI device still send DMA cycles > and then IOMMU blocks the DMA cycles of EHCI device. You've described the problem, and it is quite obviously *not* in memory.c. r~
On 30/03/21 18:33, Richard Henderson wrote: > >> Flatview_simplify() can merge many small memory ranges >> into a large one and contains EHCI dma buffers. >> For example,the merged range maybe0xc0000-0xbfffffff. >> When seabios write PAM register to change the properties >> of part of the merged range from RW to readonly, >> this action cause the merged IOVA mapping will be >> unmapped.But EHCI device still send DMA cycles >> and then IOMMU blocks the DMA cycles of EHCI device. > > You've described the problem, and it is quite obviously *not* in memory.c. Well, sort of. The problem is that neither VFIO nor KVM support atomically switching the memory map. For KVM that would be possible, for VFIO based on past discussion it would be much harder. Removing flatview_simplify() seems to be the easiest way to bypass the issue. That said, perhaps it's better to keep the simplification within a page-sized range, to avoid introducing subpages unnecessarily. Paolo
>That said, perhaps it's better to keep the simplification within a >page-sized range, to avoid introducing subpages unnecessarily. hi paolo, The sizes of all flatranges merged by flatview_simplify() are page aligned. Flatview_simplify() seems to have the opportunity to do some merging actions only when starting the virtual machine. We can temporarily remove flatview_simplify(). Thanks Felixcui
diff --git a/softmmu/memory.c b/softmmu/memory.c index d4493ef9e4..aaace8c03f 100644 --- a/softmmu/memory.c +++ b/softmmu/memory.c @@ -314,42 +314,6 @@ void flatview_unref(FlatView *view) } } -static bool can_merge(FlatRange *r1, FlatRange *r2) -{ - return int128_eq(addrrange_end(r1->addr), r2->addr.start) - && r1->mr == r2->mr - && int128_eq(int128_add(int128_make64(r1->offset_in_region), - r1->addr.size), - int128_make64(r2->offset_in_region)) - && r1->dirty_log_mask == r2->dirty_log_mask - && r1->romd_mode == r2->romd_mode - && r1->readonly == r2->readonly - && r1->nonvolatile == r2->nonvolatile; -} - -/* Attempt to simplify a view by merging adjacent ranges */ -static void flatview_simplify(FlatView *view) -{ - unsigned i, j, k; - - i = 0; - while (i < view->nr) { - j = i + 1; - while (j < view->nr - && can_merge(&view->ranges[j-1], &view->ranges[j])) { - int128_addto(&view->ranges[i].addr.size, view->ranges[j].addr.size); - ++j; - } - ++i; - for (k = i; k < j; k++) { - memory_region_unref(view->ranges[k].mr); - } - memmove(&view->ranges[i], &view->ranges[j], - (view->nr - j) * sizeof(view->ranges[j])); - view->nr -= j - i; - } -} - static bool memory_region_big_endian(MemoryRegion *mr) { #ifdef TARGET_WORDS_BIGENDIAN @@ -735,7 +699,6 @@ static FlatView *generate_memory_topology(MemoryRegion *mr) addrrange_make(int128_zero(), int128_2_64()), false, false); } - flatview_simplify(view); view->dispatch = address_space_dispatch_new(view); for (i = 0; i < view->nr; i++) {
Flatview_simplify() can merge many small memory ranges into a large one and contains EHCI dma buffers. For example,the merged range maybe0xc0000-0xbfffffff. When seabios write PAM register to change the properties of part of the merged range from RW to readonly, this action cause the merged IOVA mapping will be unmapped.But EHCI device still send DMA cycles and then IOMMU blocks the DMA cycles of EHCI device. Because the merged range is too large,there will be problems even if EHCI device is configured to not allocate buffers in low memory. So this patch wants to remove flatview_simplify() completely. Signed-off-by: FelixCuioc <FelixCui-oc@zhaoxin.com> --- softmmu/memory.c | 37 ------------------------------------- 1 file changed, 37 deletions(-)