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KVM: nVMX: Always reflect #NM VM-exits to L1 

When bit 3 (corresponding to CR0.TS) of the VMCS12 cr0_guest_host_mask
field is clear, the VMCS12 guest_cr0 field does not necessarily hold
the current value of the L2 CR0.TS bit, so the code that checked for
L2's CR0.TS bit being set was incorrect. Moreover, I'm not sure that
the CR0.TS check was adequate. (What if L2's CR0.EM was set, for
instance?)

Fortunately, lazy FPU has gone away, so L0 has lost all interest in
intercepting #NM exceptions. See commit bd7e5b0899 ("KVM: x86:
remove code for lazy FPU handling"). Therefore, there is no longer any
question of which hypervisor gets first dibs. The #NM VM-exit should
always be reflected to L1. (Note that the corresponding bit must be
set in the VMCS12 exception_bitmap field for there to be an #NM
VM-exit at all.)

Fixes: ccf9844e5d ("kvm, vmx: Really fix lazy FPU on nested guest")
Reported-by: Abhiroop Dabral <adabral@paloaltonetworks.com>
Signed-off-by: Jim Mattson <jmattson@google.com>
Reviewed-by: Peter Shier <pshier@google.com>
Tested-by: Abhiroop Dabral <adabral@paloaltonetworks.com>
Reviewed-by: Liran Alon <liran.alon@oracle.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Jim Mattson 2018-09-13 11:54:48 -07:00 committed by Paolo Bonzini
parent 214ff83d44
commit 3c6e099fa1
1 changed files with 0 additions and 8 deletions
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8
arch/x86/kvm/vmx.c
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@ -1613,11 +1613,6 @@ static inline bool is_page_fault(u32 intr_info)
return is_exception_n(intr_info, PF_VECTOR);
}
static inline bool is_no_device(u32 intr_info)
{
return is_exception_n(intr_info, NM_VECTOR);
}
static inline bool is_invalid_opcode(u32 intr_info)
{
return is_exception_n(intr_info, UD_VECTOR);
@ -9653,9 +9648,6 @@ static bool nested_vmx_exit_reflected(struct kvm_vcpu *vcpu, u32 exit_reason)
return false;
else if (is_page_fault(intr_info))
return !vmx->vcpu.arch.apf.host_apf_reason && enable_ept;
else if (is_no_device(intr_info) &&
!(vmcs12->guest_cr0 & X86_CR0_TS))
return false;
else if (is_debug(intr_info) &&
vcpu->guest_debug &
(KVM_GUESTDBG_SINGLESTEP | KVM_GUESTDBG_USE_HW_BP))