Patch "KVM: PPC: Book3S HV: Make sure we don't re-enter guest without XIVE loaded" has been added to the 4.14-stable tree

This is a note to let you know that I've just added the patch titled

KVM: PPC: Book3S HV: Make sure we don't re-enter guest without XIVE loaded

to the 4.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
kvm-ppc-book3s-hv-make-sure-we-don-t-re-enter-guest-without-xive-loaded.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Paul Mackerras <[email protected]>
Date: Thu, 11 Jan 2018 14:31:43 +1100
Subject: KVM: PPC: Book3S HV: Make sure we don't re-enter guest without XIVE loaded

From: Paul Mackerras <[email protected]>

commit 43ff3f65234061e08d234bdef5a9aadc19832b74 upstream.

This fixes a bug where it is possible to enter a guest on a POWER9 system without having the XIVE (interrupt controller) context loaded. This can happen because we unload the XIVE context from the CPU before doing the real-mode handling for machine checks. After the real-mode handler runs, it is possible that we re-enter the guest via a fast path which does not load the XIVE context.

To fix this, we move the unloading of the XIVE context to come after the real-mode machine check handler is called.

---
 arch/powerpc/kvm/book3s_hv_rmhandlers.S |   40 ++++++++++++++++----------------
 1 file changed, 20 insertions(+), 20 deletions(-)

@@ -1387,6 +1387,26 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_300)
 	blt	deliver_guest_interrupt
 
 guest_exit_cont:		/* r9 = vcpu, r12 = trap, r13 = paca */
+	/* Save more register state  */
+	mfdar	r6
+	mfdsisr	r7
+	std	r6, VCPU_DAR(r9)
+	stw	r7, VCPU_DSISR(r9)
+	/* don't overwrite fault_dar/fault_dsisr if HDSI */
+	cmpwi	r12,BOOK3S_INTERRUPT_H_DATA_STORAGE
+	beq	mc_cont
+	std	r6, VCPU_FAULT_DAR(r9)
+	stw	r7, VCPU_FAULT_DSISR(r9)
+
+	/* See if it is a machine check */
+	cmpwi	r12, BOOK3S_INTERRUPT_MACHINE_CHECK
+	beq	machine_check_realmode
+mc_cont:
+#ifdef CONFIG_KVM_BOOK3S_HV_EXIT_TIMING
+	addi	r3, r9, VCPU_TB_RMEXIT
+	mr	r4, r9
+	bl	kvmhv_accumulate_time
+#endif
 #ifdef CONFIG_KVM_XICS
 	/* We are exiting, pull the VP from the XIVE */
 	lwz	r0, VCPU_XIVE_PUSHED(r9)

@@ -1424,26 +1444,6 @@ guest_exit_cont:		/* r9 = vcpu, r12 = tr
 	eieio
 1:
 #endif /* CONFIG_KVM_XICS */
-	/* Save more register state  */
-	mfdar	r6
-	mfdsisr	r7
-	std	r6, VCPU_DAR(r9)
-	stw	r7, VCPU_DSISR(r9)
-	/* don't overwrite fault_dar/fault_dsisr if HDSI */
-	cmpwi	r12,BOOK3S_INTERRUPT_H_DATA_STORAGE
-	beq	mc_cont
-	std	r6, VCPU_FAULT_DAR(r9)
-	stw	r7, VCPU_FAULT_DSISR(r9)
-
-	/* See if it is a machine check */
-	cmpwi	r12, BOOK3S_INTERRUPT_MACHINE_CHECK
-	beq	machine_check_realmode
-mc_cont:
-#ifdef CONFIG_KVM_BOOK3S_HV_EXIT_TIMING
-	addi	r3, r9, VCPU_TB_RMEXIT
-	mr	r4, r9
-	bl	kvmhv_accumulate_time
-#endif
 
 	mr 	r3, r12
 	/* Increment exit count, poke other threads to exit */

Patches currently in stable-queue which might be from [email protected] are

queue-4.14/kvm-ppc-book3s-hv-make-sure-we-don-t-re-enter-guest-without-xive-loaded.patch queue-4.14/kvm-ppc-book3s-hv-drop-locks-before-reading-guest-memory.patch queue-4.14/kvm-ppc-book3s-pr-fix-broken-select-due-to-misspelling.patch