KVM: x86: remove unnecessary memory barriers for shared MSRs (c847fe88) · Commits · 戴 / test

There is no smp_rmb matching the smp_wmb. shared_msr_update is called from hardware_enable, which in turn is called via on_each_cpu. on_each_cpu and must imply a read memory barrier (on x86 the rmb is achieved simply through asm volatile in native_apic_mem_write). Signed-off-by:

Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/x86.c

+1 −3

Original line number	Diff line number	Diff line
		@@ -222,11 +222,9 @@ static void shared_msr_update(unsigned slot, u32 msr)
		void kvm_define_shared_msr(unsigned slot, u32 msr)
		{
		BUG_ON(slot >= KVM_NR_SHARED_MSRS);
		shared_msrs_global.msrs[slot] = msr;
		if (slot >= shared_msrs_global.nr)
		shared_msrs_global.nr = slot + 1;
		shared_msrs_global.msrs[slot] = msr;
		/* we need ensured the shared_msr_global have been updated */
		smp_wmb();
		}
		EXPORT_SYMBOL_GPL(kvm_define_shared_msr);

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