[PATCH v4 19/29] KVM: PPC: Book3S PR: enable NV reg restore for reading TM SPR at guest privilege state

[wei.guo.simon at gmail.com]

From: Simon Guo <wei.guo.simon at gmail.com>

Currently kvmppc_handle_fac() will not update NV GPRs and thus it can
return with GUEST_RESUME.

However PR KVM guest always disables MSR_TM bit at privilege state. If PR
privilege guest are trying to read TM SPRs, it will trigger TM facility
unavailable exception and fall into kvmppc_handle_fac(). Then the emulation
will be done by kvmppc_core_emulate_mfspr_pr(). The mfspr instruction can
include a RT with NV reg. So it is necessary to restore NV GPRs at this
case, to reflect the update to NV RT.

This patch make kvmppc_handle_fac() return GUEST_RESUME_NV at TM fac
exception and with guest privilege state.

Signed-off-by: Simon Guo <wei.guo.simon at gmail.com>
Reviewed-by: Paul Mackerras <paulus at ozlabs.org>
---
 arch/powerpc/kvm/book3s_pr.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/kvm/book3s_pr.c b/arch/powerpc/kvm/book3s_pr.c
index 9becca1..9a72460 100644
--- a/arch/powerpc/kvm/book3s_pr.c
+++ b/arch/powerpc/kvm/book3s_pr.c
@@ -989,6 +989,18 @@ static int kvmppc_handle_fac(struct kvm_vcpu *vcpu, ulong fac)
 		break;
 	}
 
+#ifdef CONFIG_PPC_TRANSACTIONAL_MEM
+	/* Since we disabled MSR_TM at privilege state, the mfspr instruction
+	 * for TM spr can trigger TM fac unavailable. In this case, the
+	 * emulation is handled by kvmppc_emulate_fac(), which invokes
+	 * kvmppc_emulate_mfspr() finally. But note the mfspr can include
+	 * RT for NV registers. So it need to restore those NV reg to reflect
+	 * the update.
+	 */
+	if ((fac == FSCR_TM_LG) && !(kvmppc_get_msr(vcpu) & MSR_PR))
+		return RESUME_GUEST_NV;
+#endif
+
 	return RESUME_GUEST;
 }
 
@@ -1350,8 +1362,7 @@ int kvmppc_handle_exit_pr(struct kvm_run *run, struct kvm_vcpu *vcpu,
 	}
 #ifdef CONFIG_PPC_BOOK3S_64
 	case BOOK3S_INTERRUPT_FAC_UNAVAIL:
-		kvmppc_handle_fac(vcpu, vcpu->arch.shadow_fscr >> 56);
-		r = RESUME_GUEST;
+		r = kvmppc_handle_fac(vcpu, vcpu->arch.shadow_fscr >> 56);
 		break;
 #endif
 	case BOOK3S_INTERRUPT_MACHINE_CHECK:
-- 
1.8.3.1