lkml.org 
[lkml]   [2011]   [Jan]   [31]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 06/11] xen/setup: Skip over 1st gap after System RAM.
    Date
    If the kernel is booted with dom0_mem=max:512MB and the
    machine has more than 512MB of RAM, the E820 we get is:

    Xen: 0000000000100000 - 0000000020000000 (usable)
    Xen: 00000000b7ee0000 - 00000000b7ee3000 (ACPI NVS)

    while in actuality it is:

    (XEN) 0000000000100000 - 00000000b7ee0000 (usable)
    (XEN) 00000000b7ee0000 - 00000000b7ee3000 (ACPI NVS)

    Based on that, we would determine that the "gap" between
    0x20000 -> 0xb7ee0 is not System RAM and try to assign it to
    1-1 mapping. This meant that later on when we setup the page tables
    we would try to assign those regions to DOMID_IO and the
    Xen hypervisor would fail such operation. This patch
    guards against that and sets the "gap" to be after the first
    non-RAM E820 region.

    Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
    ---
    arch/x86/xen/setup.c | 20 ++++++++++++++++++--
    1 files changed, 18 insertions(+), 2 deletions(-)

    diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
    index c2a5b5f..5b2ae49 100644
    --- a/arch/x86/xen/setup.c
    +++ b/arch/x86/xen/setup.c
    @@ -147,6 +147,7 @@ static unsigned long __init xen_set_identity(const struct e820map *e820)
    {
    phys_addr_t last = xen_initial_domain() ? 0 : ISA_END_ADDRESS;
    phys_addr_t start_pci = last;
    + phys_addr_t ram_end = last;
    int i;
    unsigned long identity = 0;

    @@ -168,11 +169,26 @@ static unsigned long __init xen_set_identity(const struct e820map *e820)
    if (start > start_pci)
    identity += set_phys_range_identity(
    PFN_UP(start_pci), PFN_DOWN(start));
    - start_pci = end;
    /* Without saving 'last' we would gooble RAM too. */
    - last = end;
    + start_pci = last = ram_end = end;
    continue;
    }
    + /* Gap found right after the 1st RAM region. Skip over it.
    + * Why? That is b/c if we pass in dom0_mem=max:512MB and
    + * have in reality 1GB, the E820 is clipped at 512MB.
    + * In xen_set_pte_init we end up calling xen_set_domain_pte
    + * which asks Xen hypervisor to alter the ownership of the MFN
    + * to DOMID_IO. We would try to set that on PFNs from 512MB
    + * up to the next System RAM region (likely from 0x20000->
    + * 0x100000). But changing the ownership on "real" RAM regions
    + * will infuriate Xen hypervisor and we will fail (WARN).
    + * So instead of trying to set IDENTITY mapping on the gap
    + * between the System RAM and the first non-RAM E820 region
    + * we start at the non-RAM E820 region.*/
    + if (ram_end && start >= ram_end) {
    + start_pci = start;
    + ram_end = 0;
    + }
    start_pci = min(start, start_pci);
    last = end;
    }
    --
    1.7.1


    \
     
     \ /
      Last update: 2011-02-01 00:13    [W:0.020 / U:34.656 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site