Messages in this thread | | | Date | Sun, 09 Mar 2014 21:12:05 +0100 | From | Paolo Bonzini <> | Subject | Re: [PATCH 4/7] KVM: vmx: Allow the guest to run with dirty debug registers |
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Il 09/03/2014 19:26, Radim Krčmář ha scritto: > > + > > + cpu_based_vm_exec_control = vmcs_read32(CPU_BASED_VM_EXEC_CONTROL); > > + cpu_based_vm_exec_control &= ~CPU_BASED_MOV_DR_EXITING; > > + vmcs_write32(CPU_BASED_VM_EXEC_CONTROL, cpu_based_vm_exec_control); > > vmcs_clear_bits() covers exactly this use-case. > (Barring the explicit bit-width.)
Good idea.
> > + > > + /* > > + * No more DR vmexits; force a reload of the debug registers > > + * and reenter on this instruction. The next vmexit will > > + * retrieve the full state of the debug registers. > > + */ > > + vcpu->arch.switch_db_regs |= KVM_DEBUGREG_WONT_EXIT; > > + return 1; > > + } > > + > > We could make the code slighly uglier and move the functional part of > this block before the previous one, so it would do both things in one > exit.
I considered this, but decided that it's unlikely for emulation to be faster than hardware---especially on those AMD CPUs that lack decode assists (and it's good for VMX and SVM code to look as similar as possible).
> (Exception handler will likely access DR too.)
Which exception handler?
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