Commit:     ce29a1f8bd99aac409904b4ca4fd700e67802556
Parent:     40ffbfad6bb79a99cc7627bdaca0ee22dec526f6
Author:     Christian Ehrhardt <[EMAIL PROTECTED]>
AuthorDate: Mon Sep 3 20:32:38 2007 +0200
Committer:  H. Peter Anvin <[EMAIL PROTECTED]>
CommitDate: Wed Sep 5 02:37:57 2007 +0100

    [x86 setup] Work around bug in Xen HVM
    Apparently XEN does not keep the contents of the 48-bit gdt_48 data
    structure that is passed to lgdt in the XEN machine state. Instead it
    appears to save the _address_ of the 48-bit descriptor
    somewhere. Unfortunately this data happens to reside on the stack and
    is probably no longer availiable at the time of the actual protected
    mode jump.
    This is Xen bug but given that there is a one-line patch to work
    around this problem, the linux kernel should probably do this.  My fix
    is to make the gdt_48 description in setup_gdt static (in setup_idt
    this is already the case). This allows the kernel to boot under
    Xen HVM again.
    Signed-off-by: Christian Ehrhardt <[EMAIL PROTECTED]>
    Signed-off-by: H. Peter Anvin <[EMAIL PROTECTED]>
 arch/i386/boot/pm.c |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/arch/i386/boot/pm.c b/arch/i386/boot/pm.c
index 6be9ca8..09fb342 100644
--- a/arch/i386/boot/pm.c
+++ b/arch/i386/boot/pm.c
@@ -122,7 +122,11 @@ static void setup_gdt(void)
                /* DS: data, read/write, 4 GB, base 0 */
                [GDT_ENTRY_BOOT_DS] = GDT_ENTRY(0xc093, 0, 0xfffff),
-       struct gdt_ptr gdt;
+       /* Xen HVM incorrectly stores a pointer to the gdt_ptr, instead
+          of the gdt_ptr contents.  Thus, make it static so it will
+          stay in memory, at least long enough that we switch to the
+          proper kernel GDT. */
+       static struct gdt_ptr gdt;
        gdt.len = sizeof(boot_gdt)-1;
        gdt.ptr = (u32)&boot_gdt + (ds() << 4);
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