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>

1 files changed, 56 insertions, 0 deletions

diff --git a/arch/powerpc/kernel/kvm_emul.S b/arch/powerpc/kernel/kvm_emul.S
index 1dac72dd6f6e..10dc4a6632fd 100644
--- a/arch/powerpc/kernel/kvm_emul.S
+++ b/arch/powerpc/kernel/kvm_emul.S
@@ -64,3 +64,59 @@ kvm_hypercall_start:
         /* 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