KVM: PPC: Fixes for PR-KVM on POWER7

Here are some fixes for PR-style KVM. With these I can successfully run a pseries (PAPR) guest under PR KVM on a POWER7. (This is all running inside a HV KVM virtual machine.) The patches are against Alex Graf's kvm-ppc-next branch.

Paul.

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.

---
This adds these registers for all CPUs; currently we don't seem to make the presence or absence of SPRs depend on the PVR, but maybe we should.

 arch/powerpc/include/asm/kvm_book3s.h |    2 ++
 arch/powerpc/kvm/book3s_emulate.c     |   16 +++++++++++++++-
 2 files changed, 17 insertions(+), 1 deletion(-)

index ab73800..c568d82 100644
@@ -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;

index b9a989d..d31a716 100644
@@ -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:

1.7.10.4

This fixes various issues in how we were handling the VSX registers that exist on POWER7 machines. First, we were running off the end of the current->thread.fpr[] array. Ultimately this was because the vcpu->arch.vsr[] array is sized to be able to store both the FP registers and the extra VSX registers (i.e. 64 entries), but PR KVM only uses it for the extra VSX registers (i.e. 32 entries).

Secondly, calling load_up_vsx() from C code is a really bad idea, because it jumps to fast_exception_return at the end, rather than returning with a blr instruction. This was causing it to jump off to a random location with random register contents, since it was using the largely uninitialized stack frame created by kvmppc_load_up_vsx.

In fact, it isn't necessary to call either __giveup_vsx or load_up_vsx, since giveup_fpu and load_up_fpu handle the extra VSX registers as well as the standard FP registers on machines with VSX. Also, since VSX instructions can access the VMX registers and the FP registers as well as the extra VSX registers, we have to load up the FP and VMX registers before we can turn on the MSR_VSX bit for the guest. Conversely, if we save away any of the VSX or FP registers, we have to turn off MSR_VSX for the guest.

To handle all this, it is more convenient for a single call to kvmppc_giveup_ext() to handle all the state saving that needs to be done, so we make it take a set of MSR bits rather than just one, and the switch statement becomes a series of if statements. Similarly kvmppc_handle_ext needs to be able to load up more than one set of registers.

---
 arch/powerpc/include/asm/reg.h       |    1 +
 arch/powerpc/kvm/book3s_exports.c    |    3 -
 arch/powerpc/kvm/book3s_pr.c         |  112 ++++++++++++++++++----------------
 arch/powerpc/kvm/book3s_rmhandlers.S |    3 -
 4 files changed, 62 insertions(+), 57 deletions(-)

index 6386086..5dc7014 100644
@@ -515,6 +515,7 @@
 #define	  SRR1_WS_DEEPER	0x00020000 /* Some resources not maintained */
 #define	  SRR1_WS_DEEP		0x00010000 /* All resources maintained */
 #define   SRR1_PROGFPE		0x00100000 /* Floating Point Enabled */
+#define   SRR1_PROGILL		0x00080000 /* Illegal instruction */
 #define   SRR1_PROGPRIV		0x00040000 /* Privileged instruction */
 #define   SRR1_PROGTRAP		0x00020000 /* Trap */
 #define   SRR1_PROGADDR		0x00010000 /* SRR0 contains subsequent addr */

index a150817..7057a02 100644
@@ -28,8 +28,5 @@ EXPORT_SYMBOL_GPL(kvmppc_load_up_fpu);
 #ifdef CONFIG_ALTIVEC
 EXPORT_SYMBOL_GPL(kvmppc_load_up_altivec);
 #endif
-#ifdef CONFIG_VSX
-EXPORT_SYMBOL_GPL(kvmppc_load_up_vsx);
-#endif
 #endif
 

index b2f8258..8f7633e 100644
@@ -234,8 +234,5 @@ define_load_up(fpu)
 #ifdef CONFIG_ALTIVEC
 define_load_up(altivec)
 #endif
-#ifdef CONFIG_VSX
-define_load_up(vsx)
-#endif
 
 #include "book3s_segment.S"

1.7.10.4

The mask of MSR bits that get transferred from the guest MSR to the shadow MSR included MSR_DE. In fact that bit only exists on Book 3E processors, and it is assigned the same bit used for MSR_BE on Book 3S processors. Since we already had MSR_BE in the mask, this just removes MSR_DE.

---
 arch/powerpc/kvm/book3s_pr.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index 15d74e5..71b7988 100644
@@ -145,7 +145,7 @@ static void kvmppc_recalc_shadow_msr(struct kvm_vcpu *vcpu)
 	ulong smsr = vcpu->arch.shared->msr;
 
 	/* Guest MSR values */
-	smsr &= MSR_FE0 | MSR_FE1 | MSR_SF | MSR_SE | MSR_BE | MSR_DE;
+	smsr &= MSR_FE0 | MSR_FE1 | MSR_SF | MSR_SE | MSR_BE;
 	/* Process MSR values */
 	smsr |= MSR_ME | MSR_RI | MSR_IR | MSR_DR | MSR_PR | MSR_EE;
 	/* External providers the guest reserved */

1.7.10.4

Thanks a lot! Applied all to kvm-ppc-next.

Alex