commit db85b8ff32c46796aa91fecb04ea1ae3411c077e
author Andreas Sandberg <andreas.sandberg@arm.com> Thu Jul 27 09:26:07 2017 +0000
committer Andreas Sandberg <andreas.sandberg@arm.com> Tue Aug 01 16:20:24 2017 +0000
tree 601211fa2486b21504883cc85f379edb1d9016b0
parent 1935cec529ac2ae7d9b31f1e55f333a0769184b5

kvm, arm: Switch to the device EQ when accessing ISA devices

ISA devices typically run in the device event queue. Previously, we
assumed that devices would perform their own EQ migrations as
needed. This isn't ideal since it means we have different conventions
for IO devices and ISA devices. Switch to doing migrations in the KVM
CPU instead to make the behavior consistent.

Change-Id: I33b74480fb2126b0786dbdbfdcfa86083384250c
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/4288
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>

src/arch/arm/kvm/armv8_cpu.cc

diff --git a/src/arch/arm/kvm/armv8_cpu.cc b/src/arch/arm/kvm/armv8_cpu.cc
index db2b9c0..209f49e 100644
--- a/src/arch/arm/kvm/armv8_cpu.cc
+++ b/src/arch/arm/kvm/armv8_cpu.cc
@@ -260,7 +260,17 @@
     }
 
     for (const auto &ri : getSysRegMap()) {
-        const uint64_t value(tc->readMiscReg(ri.idx));
+        uint64_t value;
+        if (ri.is_device) {
+            // This system register is backed by a device. This means
+            // we need to lock the device event queue.
+            EventQueue::ScopedMigration migrate(deviceEventQueue());
+
+            value = tc->readMiscReg(ri.idx);
+        } else {
+            value = tc->readMiscReg(ri.idx);
+        }
+
         DPRINTF(KvmContext, "  %s := 0x%x\n", ri.name, value);
         setOneReg(ri.kvm, value);
     }
@@ -323,10 +333,15 @@
     for (const auto &ri : getSysRegMap()) {
         const auto value(getOneRegU64(ri.kvm));
         DPRINTF(KvmContext, "  %s := 0x%x\n", ri.name, value);
-        if (ri.is_device)
+        if (ri.is_device) {
+            // This system register is backed by a device. This means
+            // we need to lock the device event queue.
+            EventQueue::ScopedMigration migrate(deviceEventQueue());
+
             tc->setMiscReg(ri.idx, value);
-        else
+        } else {
             tc->setMiscRegNoEffect(ri.idx, value);
+        }
     }
 
     PCState pc(getOneRegU64(INT_REG(regs.pc)));

src/dev/arm/generic_timer.cc

diff --git a/src/dev/arm/generic_timer.cc b/src/dev/arm/generic_timer.cc
index 6332b8f..3508674 100644
--- a/src/dev/arm/generic_timer.cc
+++ b/src/dev/arm/generic_timer.cc
@@ -318,11 +318,6 @@
 void
 GenericTimer::setMiscReg(int reg, unsigned cpu, MiscReg val)
 {
-    // This method might have been called from another context if we
-    // are running in multi-core KVM. Migrate to the SimObject's event
-    // queue to prevent surprising race conditions.
-    EventQueue::ScopedMigration migrate(eventQueue());
-
     CoreTimers &core(getTimers(cpu));
 
     switch (reg) {
@@ -415,11 +410,6 @@
 MiscReg
 GenericTimer::readMiscReg(int reg, unsigned cpu)
 {
-    // This method might have been called from another context if we
-    // are running in multi-core KVM. Migrate to the SimObject's event
-    // queue to prevent surprising race conditions.
-    EventQueue::ScopedMigration migrate(eventQueue());
-
     CoreTimers &core(getTimers(cpu));
 
     switch (reg) {