[Xen-devel] [PATCH] bimodal compatibility

[John Levon <levon@xxxxxxxxxxxxxxxxx>]

Please apply to both 3.0.4 and unstable. I've verified (on 3.0.4 and
3.0.3) that this lets us boot as PAE (on 3.0.3) and bimodally (on
3.0.4).

thanks,
john


# HG changeset patch
# User john.levon@xxxxxxx
# Date 1168289681 28800
# Node ID b6e3e5f9bc399934ae6fd9ae2f6949a500133a04
# Parent  cae900bdee460d6cae04a8a8537f4094f568b3fc
Use strstr() to look for "bimodal" string in ELF notes, to allow guests to use
"yes,bimodal", so they are correctly identified as PAE on older hypervisors.

Signed-off-by: John Levon <john.levon@xxxxxxx>

diff --git a/tools/libxc/xc_load_elf.c b/tools/libxc/xc_load_elf.c
--- a/tools/libxc/xc_load_elf.c
+++ b/tools/libxc/xc_load_elf.c
@@ -406,17 +406,19 @@ static int parseelfimage(const char *ima
     }
 
     /*
-     * A "bimodal" ELF note indicates the kernel will adjust to the
-     * current paging mode, including handling extended cr3 syntax.
-     * If we have ELF notes then PAE=yes implies that we must support
-     * the extended cr3 syntax. Otherwise we need to find the
-     * [extended-cr3] syntax in the __xen_guest string.
+     * A "bimodal" ELF note indicates the kernel will adjust to the current
+     * paging mode, including handling extended cr3 syntax.  If we have ELF
+     * notes then PAE=yes implies that we must support the extended cr3 syntax.
+     * Otherwise we need to find the [extended-cr3] syntax in the __xen_guest
+     * string. We use strstr() to look for "bimodal" to allow guests to use
+     * "yes,bimodal" or "no,bimodal" for compatibility reasons.
      */
+
     dsi->pae_kernel = PAEKERN_no;
     if ( dsi->__elfnote_section )
     {
         p = xen_elfnote_string(dsi, XEN_ELFNOTE_PAE_MODE);
-        if ( p != NULL && strncmp(p, "bimodal", 7) == 0 )
+        if ( p != NULL && strstr(p, "bimodal") != NULL )
             dsi->pae_kernel = PAEKERN_bimodal;
         else if ( p != NULL && strncmp(p, "yes", 3) == 0 )
             dsi->pae_kernel = PAEKERN_extended_cr3;
diff --git a/xen/common/elf.c b/xen/common/elf.c
--- a/xen/common/elf.c
+++ b/xen/common/elf.c
@@ -300,7 +300,7 @@ int parseelfimage(struct domain_setup_in
     if ( dsi->__elfnote_section )
     {
         p = xen_elfnote_string(dsi, XEN_ELFNOTE_PAE_MODE);
-        if ( p != NULL && strncmp(p, "bimodal", 7) == 0 )
+        if ( p != NULL && strstr(p, "bimodal") != NULL )
             dsi->pae_kernel = PAEKERN_bimodal;
         else if ( p != NULL && strncmp(p, "yes", 3) == 0 )
             dsi->pae_kernel = PAEKERN_extended_cr3;

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