diff options
Diffstat (limited to 'fix_xen_guest_on_old_EC2.patch')
| -rw-r--r-- | fix_xen_guest_on_old_EC2.patch | 34 |
1 files changed, 34 insertions, 0 deletions
diff --git a/fix_xen_guest_on_old_EC2.patch b/fix_xen_guest_on_old_EC2.patch new file mode 100644 index 000000000..e86200295 --- /dev/null +++ b/fix_xen_guest_on_old_EC2.patch @@ -0,0 +1,34 @@ + +Legacy hypervisors (RHEL 5.0 and RHEL 5.1) do not handle guest writes to +cr4 gracefully. If a guest attempts to write a bit of cr4 that is +unsupported, then the HV is so offended it crashes the domain. While +later guest kernels (such as RHEL6) don't assume the HV supports all +features, they do expect nicer responses. That assumption introduced +code that probes whether or not xsave is supported early in the boot. So +now when attempting to boot a RHEL6 guest on RHEL5.0 or RHEL5.1 an early +crash will occur. + +This patch is quite obviously an undesirable hack. The real fix for this +problem should be in the HV, and is, in later HVs. However, to support +running on old HVs, RHEL6 can take this small change. No impact will +occur for running on any RHEL HV (not even RHEL 5.5 supports xsave). +There is only potential for guest performance loss on upstream Xen. + +--- + arch/x86/xen/enlighten.c | 1 + + 1 files changed, 1 insertions(+), 0 deletions(-) + +diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c +index 52f8e19..6db3d67 100644 +--- a/arch/x86/xen/enlighten.c ++++ b/arch/x86/xen/enlighten.c +@@ -802,6 +802,7 @@ static void xen_write_cr4(unsigned long cr4) + { + cr4 &= ~X86_CR4_PGE; + cr4 &= ~X86_CR4_PSE; ++ cr4 &= ~X86_CR4_OSXSAVE; + + native_write_cr4(cr4); + } +-- +1.6.6.1 |