From mboxrd@z Thu Jan  1 00:00:00 1970
From: Hollis Blanchard <hollisb@us.ibm.com>
Date: Wed, 19 Mar 2008 23:25:20 +0000
Subject: [kvm-ppc-devel] guest panic fixed
Message-Id: <1205969120.11366.67.camel@basalt>
List-Id: <kvm-ppc.vger.kernel.org>
MIME-Version: 1.0
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To: kvm-ppc@vger.kernel.org

Thanks to some excellent debugging by Christian, we found the cause of
our annoying guest panics. We had not implemented exception priorities
(my bad), so a userspace ITLB miss was being delivered immediately after
entry to the decrementer interrupt vector. Patch follows,
http://penguinppc.org/~hollisb/kvm/ updated.

NFS root with virtio-net still doesn't work for me, but it doesn't
crash. :)

diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -68,6 +68,44 @@ static const u32 interrupt_msr_mask[16] 
 	[BOOKE_INTERRUPT_DEBUG]         = MSR_ME,
 };
 
+const unsigned char exception_priority[] = {
+	[BOOKE_INTERRUPT_DATA_STORAGE] = 0,
+	[BOOKE_INTERRUPT_INST_STORAGE] = 1,
+	[BOOKE_INTERRUPT_ALIGNMENT] = 2,
+	[BOOKE_INTERRUPT_PROGRAM] = 3,
+	[BOOKE_INTERRUPT_FP_UNAVAIL] = 4,
+	[BOOKE_INTERRUPT_SYSCALL] = 5,
+	[BOOKE_INTERRUPT_AP_UNAVAIL] = 6,
+	[BOOKE_INTERRUPT_DTLB_MISS] = 7,
+	[BOOKE_INTERRUPT_ITLB_MISS] = 8,
+	[BOOKE_INTERRUPT_MACHINE_CHECK] = 9,
+	[BOOKE_INTERRUPT_DEBUG] = 10,
+	[BOOKE_INTERRUPT_CRITICAL] = 11,
+	[BOOKE_INTERRUPT_WATCHDOG] = 12,
+	[BOOKE_INTERRUPT_EXTERNAL] = 13,
+	[BOOKE_INTERRUPT_FIT] = 14,
+	[BOOKE_INTERRUPT_DECREMENTER] = 15,
+};
+
+const unsigned char priority_exception[] = {
+	BOOKE_INTERRUPT_DATA_STORAGE,
+	BOOKE_INTERRUPT_INST_STORAGE,
+	BOOKE_INTERRUPT_ALIGNMENT,
+	BOOKE_INTERRUPT_PROGRAM,
+	BOOKE_INTERRUPT_FP_UNAVAIL,
+	BOOKE_INTERRUPT_SYSCALL,
+	BOOKE_INTERRUPT_AP_UNAVAIL,
+	BOOKE_INTERRUPT_DTLB_MISS,
+	BOOKE_INTERRUPT_ITLB_MISS,
+	BOOKE_INTERRUPT_MACHINE_CHECK,
+	BOOKE_INTERRUPT_DEBUG,
+	BOOKE_INTERRUPT_CRITICAL,
+	BOOKE_INTERRUPT_WATCHDOG,
+	BOOKE_INTERRUPT_EXTERNAL,
+	BOOKE_INTERRUPT_FIT,
+	BOOKE_INTERRUPT_DECREMENTER,
+};
+
 
 gfn_t unalias_gfn(struct kvm *kvm, gfn_t gfn)
 {
@@ -183,19 +221,21 @@ static void kvmppc_check_and_deliver_int
 static void kvmppc_check_and_deliver_interrupts(struct kvm_vcpu *vcpu)
 {
 	unsigned long *pending = &vcpu->arch.pending_exceptions;
-	int exception;
-
-	exception = find_first_bit(pending, BITS_PER_BYTE * sizeof(*pending));
-	while (exception < BOOKE_MAX_INTERRUPT) {
+	unsigned int exception;
+	unsigned int priority;
+
+	priority = find_first_bit(pending, BITS_PER_BYTE * sizeof(*pending));
+	while (priority <= BOOKE_MAX_INTERRUPT) {
+		exception = priority_exception[priority];
 		if (kvmppc_can_deliver_interrupt(vcpu, exception)) {
 			kvmppc_clear_exception(vcpu, exception);
 			kvmppc_deliver_interrupt(vcpu, exception);
 			break;
 		}
 
-		exception = find_next_bit(pending,
-		                          BITS_PER_BYTE * sizeof(*pending),
-		                          exception + 1);
+		priority = find_next_bit(pending,
+		                         BITS_PER_BYTE * sizeof(*pending),
+		                         priority + 1);
 	}
 }
 
diff --git a/include/asm-powerpc/kvm_ppc.h b/include/asm-powerpc/kvm_ppc.h
--- a/include/asm-powerpc/kvm_ppc.h
+++ b/include/asm-powerpc/kvm_ppc.h
@@ -41,6 +41,9 @@ enum emulation_result {
 	EMULATE_FAIL,         /* can't emulate this instruction */
 };
 
+extern const unsigned char exception_priority[];
+extern const unsigned char priority_exception[];
+
 extern int __kvmppc_vcpu_run(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu);
 extern char kvmppc_handlers_start[];
 extern unsigned long kvmppc_handler_len;
@@ -65,12 +68,14 @@ extern void kvmppc_44x_tlb_trace(int act
 
 static inline void kvmppc_queue_exception(struct kvm_vcpu *vcpu, int exception)
 {
-	set_bit(exception, &vcpu->arch.pending_exceptions);
+	unsigned int priority = exception_priority[exception];
+	set_bit(priority, &vcpu->arch.pending_exceptions);
 }
 
 static inline void kvmppc_clear_exception(struct kvm_vcpu *vcpu, int exception)
 {
-	clear_bit(exception, &vcpu->arch.pending_exceptions);
+	unsigned int priority = exception_priority[exception];
+	clear_bit(priority, &vcpu->arch.pending_exceptions);
 }
 
 static inline void kvmppc_set_msr(struct kvm_vcpu *vcpu, u32 new_msr)


-- 
Hollis Blanchard
IBM Linux Technology Center


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