On Wed, Dec 29, 2021, Yang Zhong wrote:
> +static void handle_nm_fault_irqoff(struct kvm_vcpu *vcpu)
> +{
> + rdmsrl(MSR_IA32_XFD_ERR, vcpu->arch.guest_fpu.xfd_err);
> + kvm_queue_exception(vcpu, NM_VECTOR);
This is still wrong, even though no additional supported is needed to support
nested XFD. If L1 wants to intercept #NM, then KVM must not inject the #NM and
must not read XFD_ERR.
That this was posted multiple times is disturbing, because kvm-unit-tests has a
test for exactly this, and running it against this series on a host without XFD
yields:
unchecked MSR access error: RDMSR from 0x1c5 at rIP: 0xffffffffa02478ee (vmx_handle_exit_irqoff+0x1de/0x240 [kvm_intel])
Call Trace:
<TASK>
kvm_arch_vcpu_ioctl_run+0x11a0/0x1fb0 [kvm]
kvm_vcpu_ioctl+0x279/0x690 [kvm]
__x64_sys_ioctl+0x83/0xb0
do_syscall_64+0x3b/0xc0
entry_SYSCALL_64_after_hwframe+0x44/0xae
</TASK>
