Report LFENCE_SERIALISE unconditionally for DE_CFG on AMD hardware and
silently drop writes.
Reported-by: Andrew Cooper <andrew.coop...@citrix.com>
Signed-off-by: Roger Pau Monné <roger....@citrix.com>
---
Changes since v2:
- Drop the bot_cpu checks and don't attempt to read the MSR, just
return LFENCE_SERIALISE unconditionally.
- Add a comment about OpenBSD panicking if writing to the MSR
triggers a #GP.
Changes since v1:
- New in this version.
---
xen/arch/x86/msr.c | 15 +++++++++++++++
1 file changed, 15 insertions(+)
diff --git a/xen/arch/x86/msr.c b/xen/arch/x86/msr.c
index a478b91f23..e84107ac7b 100644
--- a/xen/arch/x86/msr.c
+++ b/xen/arch/x86/msr.c
@@ -292,6 +292,12 @@ int guest_rdmsr(struct vcpu *v, uint32_t msr, uint64_t
*val)
*val = msrs->tsc_aux;
break;
+ case MSR_AMD64_DE_CFG:
+ if ( !(cp->x86_vendor & (X86_VENDOR_AMD | X86_VENDOR_HYGON)) )
+ goto gp_fault;
+ *val = AMD64_DE_CFG_LFENCE_SERIALISE;
+ break;
+
case MSR_AMD64_DR0_ADDRESS_MASK:
case MSR_AMD64_DR1_ADDRESS_MASK ... MSR_AMD64_DR3_ADDRESS_MASK:
if ( !cp->extd.dbext )
@@ -517,6 +523,15 @@ int guest_wrmsr(struct vcpu *v, uint32_t msr, uint64_t val)
wrmsr_tsc_aux(val);
break;
+ case MSR_AMD64_DE_CFG:
+ /*
+ * OpenBSD 6.7 will panic if writing to DE_CFG triggers a #GP:
+ * https://www.illumos.org/issues/12998
+ */
+ if ( !(cp->x86_vendor & (X86_VENDOR_AMD | X86_VENDOR_HYGON)) )
+ goto gp_fault;
+ break;
+
case MSR_AMD64_DR0_ADDRESS_MASK:
case MSR_AMD64_DR1_ADDRESS_MASK ... MSR_AMD64_DR3_ADDRESS_MASK:
if ( !cp->extd.dbext || val != (uint32_t)val )
--
2.28.0
