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    SubjectRe: [PATCH] xen/p2m: fix extra memory regions accounting
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    On 09/03/2015 02:05 PM, Roger Pau Monne wrote:
    > On systems with memory maps with ranges that don't end at page boundaries,
    > like:
    >
    > [...]
    > (XEN) 0000000000100000 - 00000000dfdf9c00 (usable)
    > (XEN) 00000000dfdf9c00 - 00000000dfe4bc00 (ACPI NVS)
    > [...]
    >
    > xen_add_extra_mem will create a protected range that ends up at 0xdfdf9c00,
    > but the function used to check if a memory address is inside of a protected
    > range works with pfns, which means that an attempt to map 0xdfdf9c00 will be
    > refused because the check is performed against 0xdfdf9000 instead of
    > 0xdfdf9c00.
    >
    > In order to fix this, make sure that the ranges that are added to the
    > xen_extra_mem array are aligned to page boundaries.
    >
    > Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
    > Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
    > Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
    > Cc: David Vrabel <david.vrabel@citrix.com>
    > Cc: Juergen Gross <jgross@suse.com>
    > Cc: xen-devel@lists.xenproject.org
    > ---
    > AFAICT this patch needs to be backported to 3.19, 4.0, 4.1 and 4.2.
    > ---
    > arch/x86/xen/setup.c | 6 ++++++
    > 1 file changed, 6 insertions(+)
    >
    > diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
    > index 55f388e..dcf5865 100644
    > --- a/arch/x86/xen/setup.c
    > +++ b/arch/x86/xen/setup.c
    > @@ -68,6 +68,9 @@ static void __init xen_add_extra_mem(phys_addr_t start, phys_addr_t size)
    > {
    > int i;
    >
    > + start = PAGE_ALIGN(start);
    > + size &= PAGE_MASK;

    This is not correct. If start wasn't page aligned and size was, you'll
    add one additional page to xen_extra_mem.

    > +
    > for (i = 0; i < XEN_EXTRA_MEM_MAX_REGIONS; i++) {
    > /* Add new region. */
    > if (xen_extra_mem[i].size == 0) {
    > @@ -92,6 +95,9 @@ static void __init xen_del_extra_mem(phys_addr_t start, phys_addr_t size)
    > int i;
    > phys_addr_t start_r, size_r;
    >
    > + start = PAGE_ALIGN(start);
    > + size &= PAGE_MASK;

    Not really needed, as xen_del_extra_mem() is called with aligned values
    only. OTOH it does no harm, as long as you correct size as above.

    > +
    > for (i = 0; i < XEN_EXTRA_MEM_MAX_REGIONS; i++) {
    > start_r = xen_extra_mem[i].start;
    > size_r = xen_extra_mem[i].size;
    >

    Juergen


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