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Commit f9208427 authored by Bharat Bhushan's avatar Bharat Bhushan Committed by Avi Kivity
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PPC: Fix race in mtmsr paravirt implementation 



The current implementation of mtmsr and mtmsrd are racy in that it does:

  * check (int_pending == 0)
  ---> host sets int_pending = 1 <---
  * write shared page
  * done

while instead we should check for int_pending after the shared page is written.

Signed-off-by: default avatarBharat Bhushan <bharat.bhushan@freescale.com>
Signed-off-by: default avatarAlexander Graf <agraf@suse.de>
Signed-off-by: default avatarAvi Kivity <avi@redhat.com>
parent 95325e6b

arch/powerpc/kernel/kvm_emul.S

+4 −6
Original line number Diff line number Diff line
@@ -167,6 +167,9 @@ maybe_stay_in_guest: 
kvm_emulate_mtmsr_reg2:

	ori	r30, r0, 0



	/* Put MSR into magic page because we don't call mtmsr */

	STL64(r30, KVM_MAGIC_PAGE + KVM_MAGIC_MSR, 0)



	/* Check if we have to fetch an interrupt */

	lwz	r31, (KVM_MAGIC_PAGE + KVM_MAGIC_INT)(0)

	cmpwi	r31, 0
@@ -174,15 +177,10 @@ kvm_emulate_mtmsr_reg2: 


	/* Check if we may trigger an interrupt */

	andi.	r31, r30, MSR_EE

	beq	no_mtmsr



	b	do_mtmsr

	bne	do_mtmsr



no_mtmsr:



	/* Put MSR into magic page because we don't call mtmsr */

	STL64(r30, KVM_MAGIC_PAGE + KVM_MAGIC_MSR, 0)



	SCRATCH_RESTORE



	/* Go back to caller */