Some variations of Linux kernels end up accessing MSR's that the Windows
Hypervisor doesn't implement which causes a GP to be returned to the guest.
This fix registers QEMU for unimplemented MSR access and globally returns 0 on
reads and ignores writes. This behavior is allows the Linux kernel to probe the
MSR with a write/read/check sequence it does often without failing the access.
Signed-off-by: Justin Terry (VM) <jute...@microsoft.com>
---
target/i386/whpx-all.c | 41 ++++++++++++++++++++++++++++++++++++++---
1 file changed, 38 insertions(+), 3 deletions(-)
diff --git a/target/i386/whpx-all.c b/target/i386/whpx-all.c
index 99501bac57..57e53e1f1f 100644
--- a/target/i386/whpx-all.c
+++ b/target/i386/whpx-all.c
@@ -932,6 +932,7 @@ static int whpx_vcpu_run(CPUState *cpu)
case WHvRunVpExitReasonX64InterruptWindow:
vcpu->window_registered = 0;
+ ret = 0;
break;
case WHvRunVpExitReasonX64Halt:
@@ -943,6 +944,40 @@ static int whpx_vcpu_run(CPUState *cpu)
ret = 1;
break;
+ case WHvRunVpExitReasonX64MsrAccess: {
+ WHV_REGISTER_VALUE reg_values[3] = {0};
+ WHV_REGISTER_NAME reg_names[3];
+ UINT32 reg_count;
+
+ reg_names[0] = WHvX64RegisterRip;
+ reg_names[1] = WHvX64RegisterRax;
+ reg_names[2] = WHvX64RegisterRdx;
+
+ reg_values[0].Reg64 =
+ vcpu->exit_ctx.VpContext.Rip +
+ vcpu->exit_ctx.VpContext.InstructionLength;
+
+ /*
+ * For all unsupported MSR access we:
+ * ignore writes
+ * return 0 on read.
+ */
+ reg_count = vcpu->exit_ctx.MsrAccess.AccessInfo.IsWrite ?
+ 1 : 3;
+
+ hr = whp_dispatch.WHvSetVirtualProcessorRegisters(
+ whpx->partition,
+ cpu->cpu_index,
+ reg_names, reg_count,
+ reg_values);
+
+ if (FAILED(hr)) {
+ error_report("WHPX: Failed to set MsrAccess state "
+ " registers, hr=%08lx", hr);
+ }
+ ret = 0;
+ break;
+ }
case WHvRunVpExitReasonX64Cpuid: {
WHV_REGISTER_VALUE reg_values[5];
WHV_REGISTER_NAME reg_names[5];
@@ -1010,7 +1045,6 @@ static int whpx_vcpu_run(CPUState *cpu)
case WHvRunVpExitReasonUnrecoverableException:
case WHvRunVpExitReasonInvalidVpRegisterValue:
case WHvRunVpExitReasonUnsupportedFeature:
- case WHvRunVpExitReasonX64MsrAccess:
case WHvRunVpExitReasonException:
default:
error_report("WHPX: Unexpected VP exit code %d",
@@ -1378,6 +1412,7 @@ static int whpx_accel_init(MachineState *ms)
}
memset(&prop, 0, sizeof(WHV_PARTITION_PROPERTY));
+ prop.ExtendedVmExits.X64MsrExit = 1;
prop.ExtendedVmExits.X64CpuidExit = 1;
hr = whp_dispatch.WHvSetPartitionProperty(
whpx->partition,
@@ -1386,8 +1421,8 @@ static int whpx_accel_init(MachineState *ms)
sizeof(WHV_PARTITION_PROPERTY));
if (FAILED(hr)) {
- error_report("WHPX: Failed to enable partition extended X64CpuidExit"
- " hr=%08lx", hr);
+ error_report("WHPX: Failed to enable partition extended X64MsrExit and"
+ " X64CpuidExit hr=%08lx", hr);
ret = -EINVAL;
goto error;
}
--
2.13.6
