On 6/7/18 1:28 PM, Ben Hutchings wrote: > On Mon, 2018-05-28 at 11:59 +0200, Greg Kroah-Hartman wrote: >> 4.4-stable review patch. If anyone has any objections, please let me know. >> >> ------------------ >> >> From: Joe Jin <joe.jin@xxxxxxxxxx> >> >> commit 4855c92dbb7b3b85c23e88ab7ca04f99b9677b41 upstream. >> >> When run raidconfig from Dom0 we found that the Xen DMA heap is reduced, >> but Dom Heap is increased by the same size. Tracing raidconfig we found >> that the related ioctl() in megaraid_sas will call dma_alloc_coherent() >> to apply memory. If the memory allocated by Dom0 is not in the DMA area, >> it will exchange memory with Xen to meet the requiment. Later drivers >> call dma_free_coherent() to free the memory, on xen_swiotlb_free_coherent() >> the check condition (dev_addr + size - 1 <= dma_mask) is always false, > > I think this was meant to say (dev_addr + size - 1 > dma_mask), i.e. Hi Ben, Yes you are right, sorry I made the mistake, thanks for catch it. Is there any way to fix description from git repo? Regards, Joe > the condition that is replaced by this commit. If that's always false, > the new condition (the logical inverse) must always be true. > > [...] >> --- a/drivers/xen/swiotlb-xen.c >> +++ b/drivers/xen/swiotlb-xen.c >> @@ -359,7 +359,7 @@ xen_swiotlb_free_coherent(struct device >> * physical address */ >> phys = xen_bus_to_phys(dev_addr); >> >> - if (((dev_addr + size - 1 > dma_mask)) || >> + if (((dev_addr + size - 1 <= dma_mask)) || >> range_straddles_page_boundary(phys, size)) >> xen_destroy_contiguous_region(phys, order); >> > > So now we will always call xen_destroy_contiguous_region(), whether or > not xen_create_contiguous_region() was called during allocation. Is > that really the intent? If so, the entire condition could be removed > to make this clear. > > Alternately, if the commit message is correct, the condition could be > simplified to range_straddles_page_boundary(...). > > But I'm not at all convinced that either of these is correct. It seems > like you need to either find a way of distinguishing between memory > allocated with or without the use of xen_create_contiguous_region(), or > to use it unconditionally. > > Ben. > -- Oracle <http://www.oracle.com> Joe Jin | IT Director ORACLE | Production Engineering and Operations 600 Oracle Parkway Redwood City, CA US 94065
