Commit 758ccc89 authored May 31, 2013 by Xiao Guangrong Committed by Gleb Natapov Jun 05, 2013

KVM: x86: drop calling kvm_mmu_zap_all in emulator_fix_hypercall



Quote Gleb's mail:

| Back then kvm->lock protected memslot access so code like:
|
| mutex_lock(&vcpu->kvm->lock);
| kvm_mmu_zap_all(vcpu->kvm);
| mutex_unlock(&vcpu->kvm->lock);
|
| which is what 7aa81cc0 does was enough to guaranty that no vcpu will
| run while code is patched. This is no longer the case and
| mutex_lock(&vcpu->kvm->lock); is gone from that code path long time ago,
| so now kvm_mmu_zap_all() there is useless and the code is incorrect.

So we drop it and it will be fixed later

Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>

parent 6ea34c9b

arch/x86/kvm/x86.c

+0 −7

Original line number	Diff line number	Diff line
		@@ -5523,13 +5523,6 @@ static int emulator_fix_hypercall(struct x86_emulate_ctxt *ctxt)
		char instruction[3];
		unsigned long rip = kvm_rip_read(vcpu);

		/*
		* Blow out the MMU to ensure that no other VCPU has an active mapping
		* to ensure that the updated hypercall appears atomically across all
		* VCPUs.
		*/
		kvm_mmu_zap_all(vcpu->kvm);

		kvm_x86_ops->patch_hypercall(vcpu, instruction);

		return emulator_write_emulated(ctxt, rip, instruction, 3, NULL);