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    xen/pv-on-hvm kexec: add quirk for Xen 3.4 and shutdown watches. · cb6b6df1
    Konrad Rzeszutek Wilk 提交于
    The commit 254d1a3f, titled
    "xen/pv-on-hvm kexec: shutdown watches from old kernel" assumes that the
    XenBus backend can deal with reading of values from:
     "control/platform-feature-xs_reset_watches":
    
        ... a patch for xenstored is required so that it
        accepts the XS_RESET_WATCHES request from a client (see changeset
        23839:42a45baf037d in xen-unstable.hg). Without the patch for xenstored
        the registration of watches will fail and some features of a PVonHVM
        guest are not available. The guest is still able to boot, but repeated
        kexec boots will fail."
    
    Sadly this is not true when using a Xen 3.4 hypervisor and booting a PVHVM
    guest. We end up hanging at:
    
      err = xenbus_scanf(XBT_NIL, "control",
                            "platform-feature-xs_reset_watches", "%d", &supported);
    
    This can easily be seen with guests hanging at xenbus_init:
    
    NX (Execute Disable) protection: active
    SMBIOS 2.4 present.
    DMI: Xen HVM domU, BIOS 3.4.0 05/13/2011
    Hypervisor detected: Xen HVM
    Xen version 3.4.
    Xen Platform PCI: I/O protocol version 1
    ... snip ..
    calling  xenbus_init+0x0/0x27e @ 1
    
    Reverting the commit or using the attached patch fixes the issue. This fix
    checks whether the hypervisor is older than 4.0 and if so does not try to
    perform the read.
    
    Fixes-Oracle-Bug: 14708233
    CC: stable@vger.kernel.org
    Acked-by: NOlaf Hering <olaf@aepfle.de>
    [v2: Added a comment in the source code]
    Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
    cb6b6df1
xenbus_xs.c 21.3 KB