lkml.org 
[lkml]   [2021]   [Sep]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    Subject[PATCH 03/12] swiotlb-xen: maintain slab count properly
    From
    Date
    Generic swiotlb code makes sure to keep the slab count a multiple of the
    number of slabs per segment. Yet even without checking whether any such
    assumption is made elsewhere, it is easy to see that xen_swiotlb_fixup()
    might alter unrelated memory when calling xen_create_contiguous_region()
    for the last segment, when that's not a full one - the function acts on
    full order-N regions, not individual pages.

    Align the slab count suitably when halving it for a retry. Add a build
    time check and a runtime one. Replace the no longer useful local
    variable "slabs" by an "order" one calculated just once, outside of the
    loop. Re-use "order" for calculating "dma_bits", and change the type of
    the latter as well as the one of "i" while touching this anyway.

    Signed-off-by: Jan Beulich <jbeulich@suse.com>

    --- a/drivers/xen/swiotlb-xen.c
    +++ b/drivers/xen/swiotlb-xen.c
    @@ -106,27 +106,26 @@ static int is_xen_swiotlb_buffer(struct

    static int xen_swiotlb_fixup(void *buf, unsigned long nslabs)
    {
    - int i, rc;
    - int dma_bits;
    + int rc;
    + unsigned int order = get_order(IO_TLB_SEGSIZE << IO_TLB_SHIFT);
    + unsigned int i, dma_bits = order + PAGE_SHIFT;
    dma_addr_t dma_handle;
    phys_addr_t p = virt_to_phys(buf);

    - dma_bits = get_order(IO_TLB_SEGSIZE << IO_TLB_SHIFT) + PAGE_SHIFT;
    + BUILD_BUG_ON(IO_TLB_SEGSIZE & (IO_TLB_SEGSIZE - 1));
    + BUG_ON(nslabs % IO_TLB_SEGSIZE);

    i = 0;
    do {
    - int slabs = min(nslabs - i, (unsigned long)IO_TLB_SEGSIZE);
    -
    do {
    rc = xen_create_contiguous_region(
    - p + (i << IO_TLB_SHIFT),
    - get_order(slabs << IO_TLB_SHIFT),
    + p + (i << IO_TLB_SHIFT), order,
    dma_bits, &dma_handle);
    } while (rc && dma_bits++ < MAX_DMA_BITS);
    if (rc)
    return rc;

    - i += slabs;
    + i += IO_TLB_SEGSIZE;
    } while (i < nslabs);
    return 0;
    }
    @@ -210,7 +209,7 @@ retry:
    error:
    if (repeat--) {
    /* Min is 2MB */
    - nslabs = max(1024UL, (nslabs >> 1));
    + nslabs = max(1024UL, ALIGN(nslabs >> 1, IO_TLB_SEGSIZE));
    bytes = nslabs << IO_TLB_SHIFT;
    pr_info("Lowering to %luMB\n", bytes >> 20);
    goto retry;
    @@ -245,7 +244,7 @@ retry:
    memblock_free(__pa(start), PAGE_ALIGN(bytes));
    if (repeat--) {
    /* Min is 2MB */
    - nslabs = max(1024UL, (nslabs >> 1));
    + nslabs = max(1024UL, ALIGN(nslabs >> 1, IO_TLB_SEGSIZE));
    bytes = nslabs << IO_TLB_SHIFT;
    pr_info("Lowering to %luMB\n", bytes >> 20);
    goto retry;
    \
     
     \ /
      Last update: 2021-09-07 14:06    [W:2.441 / U:0.076 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site