| Message ID | 20190125190134.25492-1-ehabkost@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | i386: Disable MSR_PLATFORM_INFO emulation | expand |
diff --git a/target/i386/kvm.c b/target/i386/kvm.c index 9af4542fb8..9629f25c90 100644 --- a/target/i386/kvm.c +++ b/target/i386/kvm.c @@ -1647,6 +1647,14 @@ int kvm_arch_init(MachineState *ms, KVMState *s) } } + /* + * QEMU doesn't initialize MSR_PLATFORM_INFO yet, so disable the MSR + * unconditionally until support for the MSR is properly implemented + */ + if (kvm_check_extension(s, KVM_CAP_MSR_PLATFORM_INFO)) { + kvm_vm_enable_cap(s, KVM_CAP_MSR_PLATFORM_INFO, 0); + } + return 0; }
Linux v4.12 introduced[1] emulation of MSR_PLATFORM_INFO and MSR_MISC_FEATURES_ENABLES, and enabled the MSR_PLATFORM_INFO_CPUID_FAULT bit unconditionally. This made guests incorrectly believe the VM emulates MSR_MISC_FEATURES_ENABLES properly (which is not true because QEMU has no migration code to handle the MSR). The KVM_CAP_MSR_PLATFORM_INFO capability was added[2] to Linux v4.19 to address the issue. Use it to disable emulation of MSR_PLATFORM_INFO and stop incorrectly exposing cpuid_fault to guests. References: [1] commit db2336a80489 ("KVM: x86: virtualize cpuid faulting") [2] commit 6fbbde9a1969 ("KVM: x86: Control guest reads of MSR_PLATFORM_INFO") Reported-by: Maxime Coquelin <maxime.coquelin@redhat.com> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com> --- target/i386/kvm.c | 8 ++++++++ 1 file changed, 8 insertions(+)