[PATCH v2 4/8] x86/svm: drop writes to BU_CFG on revF chips

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

We already have special casing to handle reads of this MSR for revF
chips, so do as the comment in svm_msr_read_intercept says and drop
writes. This is in preparation for changing the default MSR write
behavior, which will instead return #GP on not explicitly handled
writes.

Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
Changes since v1:
 - New in this version.
---
 xen/arch/x86/hvm/svm/svm.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/xen/arch/x86/hvm/svm/svm.c b/xen/arch/x86/hvm/svm/svm.c
index 2d0823e7e1..7586b77268 100644
--- a/xen/arch/x86/hvm/svm/svm.c
+++ b/xen/arch/x86/hvm/svm/svm.c
@@ -2125,6 +2125,12 @@ static int svm_msr_write_intercept(unsigned int msr, 
uint64_t msr_content)
         nsvm->ns_msr_hsavepa = msr_content;
         break;
 
+    case MSR_F10_BU_CFG:
+        /* See comment in svm_msr_read_intercept. */
+        if ( boot_cpu_data.x86 != 0xf )
+            goto gpf;
+        break;
+
     case MSR_AMD64_TSC_RATIO:
         if ( msr_content & TSC_RATIO_RSVD_BITS )
             goto gpf;
-- 
2.28.0