KVM: PPC: Add support for Book3S processors in hypervisor mode

This adds support for KVM running on 64-bit Book 3S processors,
specifically POWER7, in hypervisor mode.  Using hypervisor mode means
that the guest can use the processor's supervisor mode.  That means
that the guest can execute privileged instructions and access privileged
registers itself without trapping to the host.  This gives excellent
performance, but does mean that KVM cannot emulate a processor
architecture other than the one that the hardware implements.

This code assumes that the guest is running paravirtualized using the
PAPR (Power Architecture Platform Requirements) interface, which is the
interface that IBM's PowerVM hypervisor uses.  That means that existing
Linux distributions that run on IBM pSeries machines will also run
under KVM without modification.  In order to communicate the PAPR
hypercalls to qemu, this adds a new KVM_EXIT_PAPR_HCALL exit code
to include/linux/kvm.h.

Currently the choice between book3s_hv support and book3s_pr support
(i.e. the existing code, which runs the guest in user mode) has to be
made at kernel configuration time, so a given kernel binary can only
do one or the other.

This new book3s_hv code doesn't support MMIO emulation at present.
Since we are running paravirtualized guests, this isn't a serious
restriction.

With the guest running in supervisor mode, most exceptions go straight
to the guest.  We will never get data or instruction storage or segment
interrupts, alignment interrupts, decrementer interrupts, program
interrupts, single-step interrupts, etc., coming to the hypervisor from
the guest.  Therefore this introduces a new KVMTEST_NONHV macro for the
exception entry path so that we don't have to do the KVM test on entry
to those exception handlers.

We do however get hypervisor decrementer, hypervisor data storage,
hypervisor instruction storage, and hypervisor emulation assist
interrupts, so we have to handle those.

In hypervisor mode, real-mode accesses can access all of RAM, not just
a limited amount.  Therefore we put all the guest state in the vcpu.arch
and use the shadow_vcpu in the PACA only for temporary scratch space.
We allocate the vcpu with kzalloc rather than vzalloc, and we don't use
anything in the kvmppc_vcpu_book3s struct, so we don't allocate it.
We don't have a shared page with the guest, but we still need a
kvm_vcpu_arch_shared struct to store the values of various registers,
so we include one in the vcpu_arch struct.

The POWER7 processor has a restriction that all threads in a core have
to be in the same partition.  MMU-on kernel code counts as a partition
(partition 0), so we have to do a partition switch on every entry to and
exit from the guest.  At present we require the host and guest to run
in single-thread mode because of this hardware restriction.

This code allocates a hashed page table for the guest and initializes
it with HPTEs for the guest's Virtual Real Memory Area (VRMA).  We
require that the guest memory is allocated using 16MB huge pages, in
order to simplify the low-level memory management.  This also means that
we can get away without tracking paging activity in the host for now,
since huge pages can't be paged or swapped.

This also adds a few new exports needed by the book3s_hv code.

Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>

1 files changed, 21 insertions, 1 deletions

diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index 026036efcde0..3a4f379ee70f 100644
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -38,8 +38,12 @@
 
 int kvm_arch_vcpu_runnable(struct kvm_vcpu *v)
 {
+#ifndef CONFIG_KVM_BOOK3S_64_HV
         return !(v->arch.shared->msr & MSR_WE) ||
                !!(v->arch.pending_exceptions);
+#else
+        return 1;
+#endif
 }
 
 int kvmppc_kvm_pv(struct kvm_vcpu *vcpu)
@@ -184,10 +188,13 @@ int kvm_dev_ioctl_check_extension(long ext)
 #else
         case KVM_CAP_PPC_SEGSTATE:
 #endif
-        case KVM_CAP_PPC_PAIRED_SINGLES:
         case KVM_CAP_PPC_UNSET_IRQ:
         case KVM_CAP_PPC_IRQ_LEVEL:
         case KVM_CAP_ENABLE_CAP:
+                r = 1;
+                break;
+#ifndef CONFIG_KVM_BOOK3S_64_HV
+        case KVM_CAP_PPC_PAIRED_SINGLES:
         case KVM_CAP_PPC_OSI:
         case KVM_CAP_PPC_GET_PVINFO:
                 r = 1;
@@ -195,6 +202,7 @@ int kvm_dev_ioctl_check_extension(long ext)
         case KVM_CAP_COALESCED_MMIO:
                 r = KVM_COALESCED_MMIO_PAGE_OFFSET;
                 break;
+#endif
         default:
                 r = 0;
                 break;
@@ -291,6 +299,7 @@ int kvm_arch_vcpu_init(struct kvm_vcpu *vcpu)
         hrtimer_init(&vcpu->arch.dec_timer, CLOCK_REALTIME, HRTIMER_MODE_ABS);
         tasklet_init(&vcpu->arch.tasklet, kvmppc_decrementer_func, (ulong)vcpu);
         vcpu->arch.dec_timer.function = kvmppc_decrementer_wakeup;
+        vcpu->arch.dec_expires = ~(u64)0;
 
 #ifdef CONFIG_KVM_EXIT_TIMING
         mutex_init(&vcpu->arch.exit_timing_lock);
@@ -317,6 +326,7 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
         mtspr(SPRN_VRSAVE, vcpu->arch.vrsave);
 #endif
         kvmppc_core_vcpu_load(vcpu, cpu);
+        vcpu->cpu = smp_processor_id();
 }
 
 void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
@@ -325,6 +335,7 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
 #ifdef CONFIG_BOOKE
         vcpu->arch.vrsave = mfspr(SPRN_VRSAVE);
 #endif
+        vcpu->cpu = -1;
 }
 
 int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
@@ -496,6 +507,13 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
                 for (i = 0; i < 32; i++)
                         kvmppc_set_gpr(vcpu, i, gprs[i]);
                 vcpu->arch.osi_needed = 0;
+        } else if (vcpu->arch.hcall_needed) {
+                int i;
+
+                kvmppc_set_gpr(vcpu, 3, run->papr_hcall.ret);
+                for (i = 0; i < 9; ++i)
+                        kvmppc_set_gpr(vcpu, 4 + i, run->papr_hcall.args[i]);
+                vcpu->arch.hcall_needed = 0;
         }
 
         kvmppc_core_deliver_interrupts(vcpu);
@@ -518,6 +536,8 @@ int kvm_vcpu_ioctl_interrupt(struct kvm_vcpu *vcpu, struct kvm_interrupt *irq)
         if (waitqueue_active(&vcpu->wq)) {
                 wake_up_interruptible(&vcpu->wq);
                 vcpu->stat.halt_wakeup++;
+        } else if (vcpu->cpu != -1) {
+                smp_send_reschedule(vcpu->cpu);
         }
 
         return 0;