[xen staging] x86/svm: silently drop writes to SYSCFG and related MSRs

[patchbot@xxxxxxx]

commit f5b44269fc734474f3272a22ba9d426d234ed460
Author:     Roger Pau Monné <roger.pau@xxxxxxxxxx>
AuthorDate: Mon Sep 7 10:38:00 2020 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Mon Sep 7 10:38:00 2020 +0200

    x86/svm: silently drop writes to SYSCFG and related MSRs
    
    The SYSCFG, TOP_MEM1 and TOP_MEM2 MSRs are currently exposed to guests
    and writes are silently discarded. Make this explicit in the SVM code
    now, and just return default constant values when attempting to read
    any of the MSRs, while continuing to silently drop writes.
    
    Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 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 ca3bbfcbb3..af584ff5d1 100644
--- a/xen/arch/x86/hvm/svm/svm.c
+++ b/xen/arch/x86/hvm/svm/svm.c
@@ -1917,6 +1917,9 @@ static int svm_msr_read_intercept(unsigned int msr, 
uint64_t *msr_content)
             goto gpf;
         break;
 
+    case MSR_K8_SYSCFG:
+    case MSR_K8_TOP_MEM1:
+    case MSR_K8_TOP_MEM2:
     case MSR_K8_VM_CR:
         *msr_content = 0;
         break;
@@ -2094,6 +2097,9 @@ static int svm_msr_write_intercept(unsigned int msr, 
uint64_t msr_content)
             goto gpf;
         break;
 
+    case MSR_K8_TOP_MEM1:
+    case MSR_K8_TOP_MEM2:
+    case MSR_K8_SYSCFG:
     case MSR_K8_VM_CR:
         /* ignore write. handle all bits as read-only. */
         break;
--
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