KVM: PPC: Book3S PR: Emulate PURR, SPURR and DSCR registers

This adds basic emulation of the PURR and SPURR registers.  We assume
we are emulating a single-threaded core, so these advance at the same
rate as the timebase.  A Linux kernel running on a POWER7 expects to
be able to access these registers and is not prepared to handle a
program interrupt on accessing them.

This also adds a very minimal emulation of the DSCR (data stream
control register).  Writes are ignored and reads return zero.

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

2 files changed, 17 insertions, 1 deletions

diff --git a/arch/powerpc/include/asm/kvm_book3s.h b/arch/powerpc/include/asm/kvm_book3s.h
index 46763d10ad5..5a56e1c5f85 100644
--- a/arch/powerpc/include/asm/kvm_book3s.h
+++ b/arch/powerpc/include/asm/kvm_book3s.h
@@ -81,6 +81,8 @@ struct kvmppc_vcpu_book3s {
         u64 sdr1;
         u64 hior;
         u64 msr_mask;
+        u64 purr_offset;
+        u64 spurr_offset;
 #ifdef CONFIG_PPC_BOOK3S_32
         u32 vsid_pool[VSID_POOL_SIZE];
         u32 vsid_next;
diff --git a/arch/powerpc/kvm/book3s_emulate.c b/arch/powerpc/kvm/book3s_emulate.c
index b9a989dc76c..d31a716f7f2 100644
--- a/arch/powerpc/kvm/book3s_emulate.c
+++ b/arch/powerpc/kvm/book3s_emulate.c
@@ -22,6 +22,7 @@
 #include <asm/kvm_book3s.h>
 #include <asm/reg.h>
 #include <asm/switch_to.h>
+#include <asm/time.h>
 
 #define OP_19_XOP_RFID          18
 #define OP_19_XOP_RFI           50
@@ -395,6 +396,12 @@ int kvmppc_core_emulate_mtspr(struct kvm_vcpu *vcpu, int sprn, ulong spr_val)
                     (mfmsr() & MSR_HV))
                         vcpu->arch.hflags |= BOOK3S_HFLAG_DCBZ32;
                 break;
+        case SPRN_PURR:
+                to_book3s(vcpu)->purr_offset = spr_val - get_tb();
+                break;
+        case SPRN_SPURR:
+                to_book3s(vcpu)->spurr_offset = spr_val - get_tb();
+                break;
         case SPRN_GQR0:
         case SPRN_GQR1:
         case SPRN_GQR2:
@@ -412,6 +419,7 @@ int kvmppc_core_emulate_mtspr(struct kvm_vcpu *vcpu, int sprn, ulong spr_val)
         case SPRN_CTRLF:
         case SPRN_CTRLT:
         case SPRN_L2CR:
+        case SPRN_DSCR:
         case SPRN_MMCR0_GEKKO:
         case SPRN_MMCR1_GEKKO:
         case SPRN_PMC1_GEKKO:
@@ -483,9 +491,15 @@ int kvmppc_core_emulate_mfspr(struct kvm_vcpu *vcpu, int sprn, ulong *spr_val)
                 *spr_val = to_book3s(vcpu)->hid[5];
                 break;
         case SPRN_CFAR:
-        case SPRN_PURR:
+        case SPRN_DSCR:
                 *spr_val = 0;
                 break;
+        case SPRN_PURR:
+                *spr_val = get_tb() + to_book3s(vcpu)->purr_offset;
+                break;
+        case SPRN_SPURR:
+                *spr_val = get_tb() + to_book3s(vcpu)->purr_offset;
+                break;
         case SPRN_GQR0:
         case SPRN_GQR1:
         case SPRN_GQR2: