Add a function to set per-cpu ibs_flags based on an active or inactive
PreventHostIBS window.
MSR_AMD64_IBSFETCHCTL[IbsFetchEn] and MSR_AMD64_IBSOPCTL[IbsOpEn] bits
need to be cleared for PreventHostIBS feature to be enabled before VMRUN
is executed.
ENABLE bit and VALID bit for MSR_AMD64_IBSFETCHCTL are contained in the
same MSR and same is the case with MSR_AMD64_IBSOPCTL.
Consider the following scenario:
- The IBS MSR which has ENABLE bit set and VALID bit clear is read.
- During the process of clearing the ENABLE bit and writing the IBS MSR
to disable IBS, an IBS event can occur that sets the VALID bit.
- The write operation on IBS MSR can clear the newly set VALID bit.
- Since this situation is occurring in the CLGI/STGI window
(PreventHostIBS window), the actual NMI is not taken.
- Once VMRUN is issued, it will exit with VMEXIT_NMI. As soon as STGI is
executed, the pending NMI will trigger.
- The IBS NMI handler checks for the VALID bit to determine if the NMI
is generated because of IBS.
- Since VALID bit is now clear, it doesn't recognize that an IBS event
is occurred. Due to this reason, the dazed and confused unknown NMI
messages are generated.
amd_prevent_hostibs_window() is added to avoid these messages when
PreventHostIBS window is active and PreventHostIBS feature is enabled
for the guest.
Signed-off-by: Manali Shukla <manali.shukla@xxxxxxx>
---
arch/x86/events/amd/ibs.c | 64 +++++++++++++++++++++++++++++++
arch/x86/include/asm/perf_event.h | 20 ++++++++++
2 files changed, 84 insertions(+)
diff --git a/arch/x86/events/amd/ibs.c b/arch/x86/events/amd/ibs.c
index da3f5ebac4e1..e96a4c9ff4ba 100644
--- a/arch/x86/events/amd/ibs.c
+++ b/arch/x86/events/amd/ibs.c
@@ -30,7 +30,9 @@ static u32 ibs_caps;
#define IBS_FETCH_CONFIG_MASK (IBS_FETCH_RAND_EN | IBS_FETCH_MAX_CNT)
#define IBS_OP_CONFIG_MASK IBS_OP_MAX_CNT
+#define PREVENT_HOSTIBS_WINDOW BIT(0)
+static DEFINE_PER_CPU(unsigned int, ibs_flags);
/*
* IBS states:
@@ -1035,6 +1037,18 @@ static int perf_ibs_handle_irq(struct perf_ibs *perf_ibs, struct pt_regs *iregs)
if (test_and_clear_bit(IBS_STOPPED, pcpu->state))
return 1;
+ /*
+ * Catch NMIs generated in an active PreventHostIBS window:
+ * incoming NMIs from an active PreventHostIBS window might have
+ * the VALID bit cleared when it is supposed to be set due to
+ * a race. The reason for the race is ENABLE and VALID bits for
+ * MSR_AMD64_IBSFETCHCTL and MSR_AMD64_IBSOPCTL being in their
+ * same respective MSRs. Ignore all such NMIs and treat them as
+ * handled.
+ */
+ if (__this_cpu_read(ibs_flags) & PREVENT_HOSTIBS_WINDOW)
+ return 1;
+
return 0;
}
@@ -1540,3 +1554,53 @@ static __init int amd_ibs_init(void)
/* Since we need the pci subsystem to init ibs we can't do this earlier: */
device_initcall(amd_ibs_init);
+
+void amd_prevent_hostibs_window(bool active)
+{
+ if (active)
+ __this_cpu_write(ibs_flags,
+ __this_cpu_read(ibs_flags) |
+ PREVENT_HOSTIBS_WINDOW);
+ else
+ __this_cpu_write(ibs_flags,
+ __this_cpu_read(ibs_flags) &
+ ~PREVENT_HOSTIBS_WINDOW);
+}
+EXPORT_SYMBOL_GPL(amd_prevent_hostibs_window);
+
+bool amd_disable_ibs_fetch(u64 *ibs_fetch_ctl)
+{
+ *ibs_fetch_ctl = __rdmsr(MSR_AMD64_IBSFETCHCTL);
+ if (!(*ibs_fetch_ctl & IBS_FETCH_ENABLE))
+ return false;
+
+ native_wrmsrl(MSR_AMD64_IBSFETCHCTL,
+ *ibs_fetch_ctl & ~IBS_FETCH_ENABLE);
+
+ return true;
+}
+EXPORT_SYMBOL(amd_disable_ibs_fetch);
+
+bool amd_disable_ibs_op(u64 *ibs_op_ctl)
+{
+ *ibs_op_ctl = __rdmsr(MSR_AMD64_IBSOPCTL);
+ if (!(*ibs_op_ctl & IBS_OP_ENABLE))
+ return false;
+
+ native_wrmsrl(MSR_AMD64_IBSOPCTL, *ibs_op_ctl & ~IBS_OP_ENABLE);
+
+ return true;
+}
+EXPORT_SYMBOL(amd_disable_ibs_op);
+
+void amd_restore_ibs_fetch(u64 ibs_fetch_ctl)
+{
+ native_wrmsrl(MSR_AMD64_IBSFETCHCTL, ibs_fetch_ctl);
+}
+EXPORT_SYMBOL(amd_restore_ibs_fetch);
+
+void amd_restore_ibs_op(u64 ibs_op_ctl)
+{
+ native_wrmsrl(MSR_AMD64_IBSOPCTL, ibs_op_ctl);
+}
+EXPORT_SYMBOL(amd_restore_ibs_op);
diff --git a/arch/x86/include/asm/perf_event.h b/arch/x86/include/asm/perf_event.h
index 5d0f6891ae61..1005505e23b1 100644
--- a/arch/x86/include/asm/perf_event.h
+++ b/arch/x86/include/asm/perf_event.h
@@ -561,6 +561,26 @@ static inline void intel_pt_handle_vmx(int on)
}
#endif
+#if defined(CONFIG_X86_LOCAL_APIC) && defined(CONFIG_CPU_SUP_AMD)
+extern void amd_prevent_hostibs_window(bool active);
+extern bool amd_disable_ibs_fetch(u64 *ibs_fetch_ctl);
+extern bool amd_disable_ibs_op(u64 *ibs_op_ctl);
+extern void amd_restore_ibs_fetch(u64 ibs_fetch_ctl);
+extern void amd_restore_ibs_op(u64 ibs_op_ctl);
+#else
+static inline void amd_prevent_hostibs_window(bool active) {}
+static inline bool amd_disable_ibs_fetch(u64 *ibs_fetch_ctl)
+{
+ return false;
+}
+static inline bool amd_disable_ibs_op(u64 *ibs_op_ctl)
+{
+ return false;
+}
+static inline void amd_restore_ibs_fetch(u64 ibs_fetch_ctl) {}
+static inline void amd_restore_ibs_op(u64 ibs_op_ctl) {}
+#endif
+
#if defined(CONFIG_PERF_EVENTS) && defined(CONFIG_CPU_SUP_AMD)
extern void amd_pmu_enable_virt(void);
extern void amd_pmu_disable_virt(void);
--
2.34.1
