[Xen-changelog] [xen stable-4.6] x86/vPMU: do not clobber IA32_MISC_ENABLE

[patchbot@xxxxxxx]

commit dc8c86bb9771843c9cd63c9240b642e8905ad968
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Fri Mar 18 08:04:12 2016 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Fri Mar 18 08:04:12 2016 +0100

    x86/vPMU: do not clobber IA32_MISC_ENABLE
    
    The VMX RDMSR intercept for MSR_IA32_MISC_ENABLE falls through into
    vpmu_do_rdmsr(), so that core2_vpmu_do_rdmsr() may play with the PTS and 
PEBS
    UNAVAIL bits.
    
    Some 64bit Windows include IA32_MISC_ENABLE in the set of items checked by
    PatchGuard, and will suffer a BSOD 0x109 CRITICAL_STRUCTURE_CORRUPTION if 
the
    contents change on migrate.
    
    The vPMU infrastructure should not clobber IA32_MISC_ENABLE at all.
    
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Reviewed-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
    master commit: 0aa1330aac92fd75f185c9b354396014178fe95d
    master date: 2016-03-07 17:46:25 +0100
---
 xen/arch/x86/cpu/vpmu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xen/arch/x86/cpu/vpmu.c b/xen/arch/x86/cpu/vpmu.c
index d870dcc..48b2bc0 100644
--- a/xen/arch/x86/cpu/vpmu.c
+++ b/xen/arch/x86/cpu/vpmu.c
@@ -140,7 +140,7 @@ int vpmu_do_msr(unsigned int msr, uint64_t *msr_content,
     return ret;
 
  nop:
-    if ( !is_write )
+    if ( !is_write && (msr != MSR_IA32_MISC_ENABLE) )
         *msr_content = 0;
 
     return 0;
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.6

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