KVM: PPC: PV mtmsrd L=1
The PowerPC ISA has a special instruction for mtmsr that only changes the EE
and RI bits, namely the L=1 form.
Since that one is reasonably often occuring and simple to implement, let's
go with this first. Writing EE=0 is always just a store. Doing EE=1 also
requires us to check for pending interrupts and if necessary exit back to the
hypervisor.
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/arch/powerpc/kernel/kvm_emul.S b/arch/powerpc/kernel/kvm_emul.S
index 1dac72d..10dc4a6 100644
--- a/arch/powerpc/kernel/kvm_emul.S
+++ b/arch/powerpc/kernel/kvm_emul.S
@@ -64,3 +64,59 @@
/* Disable critical section. We are critical if \
shared->critical == r1 and r2 is always != r1 */ \
STL64(r2, KVM_MAGIC_PAGE + KVM_MAGIC_CRITICAL, 0);
+
+.global kvm_emulate_mtmsrd
+kvm_emulate_mtmsrd:
+
+ SCRATCH_SAVE
+
+ /* Put MSR & ~(MSR_EE|MSR_RI) in r31 */
+ LL64(r31, KVM_MAGIC_PAGE + KVM_MAGIC_MSR, 0)
+ lis r30, (~(MSR_EE | MSR_RI))@h
+ ori r30, r30, (~(MSR_EE | MSR_RI))@l
+ and r31, r31, r30
+
+ /* OR the register's (MSR_EE|MSR_RI) on MSR */
+kvm_emulate_mtmsrd_reg:
+ andi. r30, r0, (MSR_EE|MSR_RI)
+ or r31, r31, r30
+
+ /* Put MSR back into magic page */
+ STL64(r31, 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
+ beq+ no_check
+
+ /* Check if we may trigger an interrupt */
+ andi. r30, r30, MSR_EE
+ beq no_check
+
+ SCRATCH_RESTORE
+
+ /* Nag hypervisor */
+ tlbsync
+
+ b kvm_emulate_mtmsrd_branch
+
+no_check:
+
+ SCRATCH_RESTORE
+
+ /* Go back to caller */
+kvm_emulate_mtmsrd_branch:
+ b .
+kvm_emulate_mtmsrd_end:
+
+.global kvm_emulate_mtmsrd_branch_offs
+kvm_emulate_mtmsrd_branch_offs:
+ .long (kvm_emulate_mtmsrd_branch - kvm_emulate_mtmsrd) / 4
+
+.global kvm_emulate_mtmsrd_reg_offs
+kvm_emulate_mtmsrd_reg_offs:
+ .long (kvm_emulate_mtmsrd_reg - kvm_emulate_mtmsrd) / 4
+
+.global kvm_emulate_mtmsrd_len
+kvm_emulate_mtmsrd_len:
+ .long (kvm_emulate_mtmsrd_end - kvm_emulate_mtmsrd) / 4