KVM: PPC: Book3S HV: Fix endianness of instruction obtained from HEIR register

paulusmack · agraf · commit 4a157d61b48c · 2014-12-17T13:50:39.000+01:00
There are two ways in which a guest instruction can be obtained from
the guest in the guest exit code in book3s_hv_rmhandlers.S.  If the
exit was caused by a Hypervisor Emulation interrupt (i.e. an illegal
instruction), the offending instruction is in the HEIR register
(Hypervisor Emulation Instruction Register).  If the exit was caused
by a load or store to an emulated MMIO device, we load the instruction
from the guest by turning data relocation on and loading the instruction
with an lwz instruction.

Unfortunately, in the case where the guest has opposite endianness to
the host, these two methods give results of different endianness, but
both get put into vcpu-&gt;arch.last_inst.  The HEIR value has been loaded
using guest endianness, whereas the lwz will load the instruction using
host endianness.  The rest of the code that uses vcpu-&gt;arch.last_inst
assumes it was loaded using host endianness.

To fix this, we define a new vcpu field to store the HEIR value.  Then,
in kvmppc_handle_exit_hv(), we transfer the value from this new field to
vcpu-&gt;arch.last_inst, doing a byte-swap if the guest and host endianness
differ.

Signed-off-by: Paul Mackerras &lt;paulus@samba.org&gt;
Signed-off-by: Alexander Graf &lt;agraf@suse.de&gt;
diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h
@@ -651,6 +651,8 @@ struct kvm_vcpu_arch {
 	spinlock_t tbacct_lock;
 	u64 busy_stolen;
 	u64 busy_preempt;
+
+	u32 emul_inst;
 #endif
 };
 
diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c
@@ -498,6 +498,7 @@ int main(void)
 	DEFINE(VCPU_DAR, offsetof(struct kvm_vcpu, arch.shregs.dar));
 	DEFINE(VCPU_VPA, offsetof(struct kvm_vcpu, arch.vpa.pinned_addr));
 	DEFINE(VCPU_VPA_DIRTY, offsetof(struct kvm_vcpu, arch.vpa.dirty));
+	DEFINE(VCPU_HEIR, offsetof(struct kvm_vcpu, arch.emul_inst));
 #endif
 #ifdef CONFIG_PPC_BOOK3S
 	DEFINE(VCPU_VCPUID, offsetof(struct kvm_vcpu, vcpu_id));
diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
@@ -831,6 +831,10 @@ static int kvmppc_handle_exit_hv(struct kvm_run *run, struct kvm_vcpu *vcpu,
 	 * Accordingly return to Guest or Host.
 	 */
 	case BOOK3S_INTERRUPT_H_EMUL_ASSIST:
+		if (vcpu->arch.emul_inst != KVM_INST_FETCH_FAILED)
+			vcpu->arch.last_inst = kvmppc_need_byteswap(vcpu) ?
+				swab32(vcpu->arch.emul_inst) :
+				vcpu->arch.emul_inst;
 		if (vcpu->guest_debug & KVM_GUESTDBG_USE_SW_BP) {
 			r = kvmppc_emulate_debug_inst(run, vcpu);
 		} else {
diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
@@ -983,13 +983,13 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
 
 	stw	r12,VCPU_TRAP(r9)
 
-	/* Save HEIR (HV emulation assist reg) in last_inst
+	/* Save HEIR (HV emulation assist reg) in emul_inst
 	   if this is an HEI (HV emulation interrupt, e40) */
 	li	r3,KVM_INST_FETCH_FAILED
 	cmpwi	r12,BOOK3S_INTERRUPT_H_EMUL_ASSIST
 	bne	11f
 	mfspr	r3,SPRN_HEIR
-11:	stw	r3,VCPU_LAST_INST(r9)
+11:	stw	r3,VCPU_HEIR(r9)
 
 	/* these are volatile across C function calls */
 	mfctr	r3
