MIPS: KVM: Add MSA exception handling

Add guest exception handling for MIPS SIMD Architecture (MSA) floating
point exceptions and MSA disabled exceptions.

MSA floating point exceptions from the guest need passing to the guest
kernel, so for these a guest MSAFPE is emulated.

MSA disabled exceptions are normally handled by passing a reserved
instruction exception to the guest (because no guest MSA was supported),
but the hypervisor can now handle them if the guest has MSA by passing
an MSA disabled exception to the guest, or if the guest has MSA enabled
by transparently restoring the guest MSA context and enabling MSA and
the FPU.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Paul Burton <paul.burton@imgtec.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Gleb Natapov <gleb@kernel.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org

diff --git a/arch/mips/include/asm/kvm_host.h b/arch/mips/include/asm/kvm_host.h
index 1dc0dca15cbd746962f2184e224902bb389c5454..4c25823563fe16dfe8f4008351c111eb0dd5c4ad 100644 (file)
--- a/arch/mips/include/asm/kvm_host.h
+++ b/arch/mips/include/asm/kvm_host.h
@@ -123,7 +123,9 @@ struct kvm_vcpu_stat {
        u32 resvd_inst_exits;
        u32 break_inst_exits;
        u32 trap_inst_exits;
+       u32 msa_fpe_exits;
        u32 fpe_exits;
+       u32 msa_disabled_exits;
        u32 flush_dcache_exits;
        u32 halt_successful_poll;
        u32 halt_wakeup;
@@ -144,7 +146,9 @@ enum kvm_mips_exit_types {
        RESVD_INST_EXITS,
        BREAK_INST_EXITS,
        TRAP_INST_EXITS,
+       MSA_FPE_EXITS,
        FPE_EXITS,
+       MSA_DISABLED_EXITS,
        FLUSH_DCACHE_EXITS,
        MAX_KVM_MIPS_EXIT_TYPES
 };
@@ -305,6 +309,7 @@ enum mips_mmu_types {
  */
 #define T_TRAP                 13      /* Trap instruction */
 #define T_VCEI                 14      /* Virtual coherency exception */
+#define T_MSAFPE               14      /* MSA floating point exception */
 #define T_FPE                  15      /* Floating point exception */
 #define T_MSADIS               21      /* MSA disabled exception */
 #define T_WATCH                        23      /* Watch address reference */
@@ -601,6 +606,7 @@ struct kvm_mips_callbacks {
        int (*handle_res_inst)(struct kvm_vcpu *vcpu);
        int (*handle_break)(struct kvm_vcpu *vcpu);
        int (*handle_trap)(struct kvm_vcpu *vcpu);
+       int (*handle_msa_fpe)(struct kvm_vcpu *vcpu);
        int (*handle_fpe)(struct kvm_vcpu *vcpu);
        int (*handle_msa_disabled)(struct kvm_vcpu *vcpu);
        int (*vm_init)(struct kvm *kvm);
@@ -756,11 +762,21 @@ extern enum emulation_result kvm_mips_emulate_trap_exc(unsigned long cause,
                                                       struct kvm_run *run,
                                                       struct kvm_vcpu *vcpu);
 
+extern enum emulation_result kvm_mips_emulate_msafpe_exc(unsigned long cause,
+                                                        uint32_t *opc,
+                                                        struct kvm_run *run,
+                                                        struct kvm_vcpu *vcpu);
+
 extern enum emulation_result kvm_mips_emulate_fpe_exc(unsigned long cause,
                                                      uint32_t *opc,
                                                      struct kvm_run *run,
                                                      struct kvm_vcpu *vcpu);
 
+extern enum emulation_result kvm_mips_emulate_msadis_exc(unsigned long cause,
+                                                        uint32_t *opc,
+                                                        struct kvm_run *run,
+                                                        struct kvm_vcpu *vcpu);
+
 extern enum emulation_result kvm_mips_complete_mmio_load(struct kvm_vcpu *vcpu,
                                                         struct kvm_run *run);
 

diff --git a/arch/mips/kvm/emulate.c b/arch/mips/kvm/emulate.c
index 07f554c72cb87398431ced5ecc82e4b7fc64d9c9..6230f376a44e7ab6f09041c4b805e54e59468489 100644 (file)
--- a/arch/mips/kvm/emulate.c
+++ b/arch/mips/kvm/emulate.c
@@ -2179,6 +2179,41 @@ enum emulation_result kvm_mips_emulate_trap_exc(unsigned long cause,
        return er;
 }
 
+enum emulation_result kvm_mips_emulate_msafpe_exc(unsigned long cause,
+                                                 uint32_t *opc,
+                                                 struct kvm_run *run,
+                                                 struct kvm_vcpu *vcpu)
+{
+       struct mips_coproc *cop0 = vcpu->arch.cop0;
+       struct kvm_vcpu_arch *arch = &vcpu->arch;
+       enum emulation_result er = EMULATE_DONE;
+
+       if ((kvm_read_c0_guest_status(cop0) & ST0_EXL) == 0) {
+               /* save old pc */
+               kvm_write_c0_guest_epc(cop0, arch->pc);
+               kvm_set_c0_guest_status(cop0, ST0_EXL);
+
+               if (cause & CAUSEF_BD)
+                       kvm_set_c0_guest_cause(cop0, CAUSEF_BD);
+               else
+                       kvm_clear_c0_guest_cause(cop0, CAUSEF_BD);
+
+               kvm_debug("Delivering MSAFPE @ pc %#lx\n", arch->pc);
+
+               kvm_change_c0_guest_cause(cop0, (0xff),
+                                         (T_MSAFPE << CAUSEB_EXCCODE));
+
+               /* Set PC to the exception entry point */
+               arch->pc = KVM_GUEST_KSEG0 + 0x180;
+
+       } else {
+               kvm_err("Trying to deliver MSAFPE when EXL is already set\n");
+               er = EMULATE_FAIL;
+       }
+
+       return er;
+}
+
 enum emulation_result kvm_mips_emulate_fpe_exc(unsigned long cause,
                                               uint32_t *opc,
                                               struct kvm_run *run,
@@ -2214,6 +2249,41 @@ enum emulation_result kvm_mips_emulate_fpe_exc(unsigned long cause,
        return er;
 }
 
+enum emulation_result kvm_mips_emulate_msadis_exc(unsigned long cause,
+                                                 uint32_t *opc,
+                                                 struct kvm_run *run,
+                                                 struct kvm_vcpu *vcpu)
+{
+       struct mips_coproc *cop0 = vcpu->arch.cop0;
+       struct kvm_vcpu_arch *arch = &vcpu->arch;
+       enum emulation_result er = EMULATE_DONE;
+
+       if ((kvm_read_c0_guest_status(cop0) & ST0_EXL) == 0) {
+               /* save old pc */
+               kvm_write_c0_guest_epc(cop0, arch->pc);
+               kvm_set_c0_guest_status(cop0, ST0_EXL);
+
+               if (cause & CAUSEF_BD)
+                       kvm_set_c0_guest_cause(cop0, CAUSEF_BD);
+               else
+                       kvm_clear_c0_guest_cause(cop0, CAUSEF_BD);
+
+               kvm_debug("Delivering MSADIS @ pc %#lx\n", arch->pc);
+
+               kvm_change_c0_guest_cause(cop0, (0xff),
+                                         (T_MSADIS << CAUSEB_EXCCODE));
+
+               /* Set PC to the exception entry point */
+               arch->pc = KVM_GUEST_KSEG0 + 0x180;
+
+       } else {
+               kvm_err("Trying to deliver MSADIS when EXL is already set\n");
+               er = EMULATE_FAIL;
+       }
+
+       return er;
+}
+
 /* ll/sc, rdhwr, sync emulation */
 
 #define OPCODE 0xfc000000
@@ -2421,6 +2491,7 @@ enum emulation_result kvm_mips_check_privilege(unsigned long cause,
                case T_BREAK:
                case T_RES_INST:
                case T_TRAP:
+               case T_MSAFPE:
                case T_FPE:
                case T_MSADIS:
                        break;

diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c
index a17f21015a0b02edc65ef5b4bdbbf3176cd2cbbd..e02c7e5a12ffe8e390fbd46fb8dd570fa7280536 100644 (file)
--- a/arch/mips/kvm/mips.c
+++ b/arch/mips/kvm/mips.c
@@ -50,7 +50,9 @@ struct kvm_stats_debugfs_item debugfs_entries[] = {
        { "resvd_inst",   VCPU_STAT(resvd_inst_exits),   KVM_STAT_VCPU },
        { "break_inst",   VCPU_STAT(break_inst_exits),   KVM_STAT_VCPU },
        { "trap_inst",    VCPU_STAT(trap_inst_exits),    KVM_STAT_VCPU },
+       { "msa_fpe",      VCPU_STAT(msa_fpe_exits),      KVM_STAT_VCPU },
        { "fpe",          VCPU_STAT(fpe_exits),          KVM_STAT_VCPU },
+       { "msa_disabled", VCPU_STAT(msa_disabled_exits), KVM_STAT_VCPU },
        { "flush_dcache", VCPU_STAT(flush_dcache_exits), KVM_STAT_VCPU },
        { "halt_successful_poll", VCPU_STAT(halt_successful_poll), KVM_STAT_VCPU },
        { "halt_wakeup",  VCPU_STAT(halt_wakeup),        KVM_STAT_VCPU },
@@ -1256,6 +1258,12 @@ int kvm_mips_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu)
                ret = kvm_mips_callbacks->handle_trap(vcpu);
                break;
 
+       case T_MSAFPE:
+               ++vcpu->stat.msa_fpe_exits;
+               trace_kvm_exit(vcpu, MSA_FPE_EXITS);
+               ret = kvm_mips_callbacks->handle_msa_fpe(vcpu);
+               break;
+
        case T_FPE:
                ++vcpu->stat.fpe_exits;
                trace_kvm_exit(vcpu, FPE_EXITS);
@@ -1263,6 +1271,8 @@ int kvm_mips_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu)
                break;
 
        case T_MSADIS:
+               ++vcpu->stat.msa_disabled_exits;
+               trace_kvm_exit(vcpu, MSA_DISABLED_EXITS);
                ret = kvm_mips_callbacks->handle_msa_disabled(vcpu);
                break;
 

diff --git a/arch/mips/kvm/stats.c b/arch/mips/kvm/stats.c
index 3843828f3b91f2d957404ddf7ffe4db498cc1049..888bb67070ac6d1139a7f06f5958e180680511ef 100644 (file)
--- a/arch/mips/kvm/stats.c
+++ b/arch/mips/kvm/stats.c
@@ -26,7 +26,9 @@ char *kvm_mips_exit_types_str[MAX_KVM_MIPS_EXIT_TYPES] = {
        "Reserved Inst",
        "Break Inst",
        "Trap Inst",
+       "MSA FPE",
        "FPE",
+       "MSA Disabled",
        "D-Cache Flushes",
 };
 

diff --git a/arch/mips/kvm/trap_emul.c b/arch/mips/kvm/trap_emul.c
index 421d5b815f24bba3af41eb520cc9629092f32f3e..d836ed5b0bc7ea38e36350304a6238a520e0d74d 100644 (file)
--- a/arch/mips/kvm/trap_emul.c
+++ b/arch/mips/kvm/trap_emul.c
@@ -362,6 +362,24 @@ static int kvm_trap_emul_handle_trap(struct kvm_vcpu *vcpu)
        return ret;
 }
 
+static int kvm_trap_emul_handle_msa_fpe(struct kvm_vcpu *vcpu)
+{
+       struct kvm_run *run = vcpu->run;
+       uint32_t __user *opc = (uint32_t __user *)vcpu->arch.pc;
+       unsigned long cause = vcpu->arch.host_cp0_cause;
+       enum emulation_result er = EMULATE_DONE;
+       int ret = RESUME_GUEST;
+
+       er = kvm_mips_emulate_msafpe_exc(cause, opc, run, vcpu);
+       if (er == EMULATE_DONE) {
+               ret = RESUME_GUEST;
+       } else {
+               run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
+               ret = RESUME_HOST;
+       }
+       return ret;
+}
+
 static int kvm_trap_emul_handle_fpe(struct kvm_vcpu *vcpu)
 {
        struct kvm_run *run = vcpu->run;
@@ -380,16 +398,36 @@ static int kvm_trap_emul_handle_fpe(struct kvm_vcpu *vcpu)
        return ret;
 }
 
+/**
+ * kvm_trap_emul_handle_msa_disabled() - Guest used MSA while disabled in root.
+ * @vcpu:      Virtual CPU context.
+ *
+ * Handle when the guest attempts to use MSA when it is disabled.
+ */
 static int kvm_trap_emul_handle_msa_disabled(struct kvm_vcpu *vcpu)
 {
+       struct mips_coproc *cop0 = vcpu->arch.cop0;
        struct kvm_run *run = vcpu->run;
        uint32_t __user *opc = (uint32_t __user *) vcpu->arch.pc;
        unsigned long cause = vcpu->arch.host_cp0_cause;
        enum emulation_result er = EMULATE_DONE;
        int ret = RESUME_GUEST;
 
-       /* No MSA supported in guest, guest reserved instruction exception */
-       er = kvm_mips_emulate_ri_exc(cause, opc, run, vcpu);
+       if (!kvm_mips_guest_has_msa(&vcpu->arch) ||
+           (kvm_read_c0_guest_status(cop0) & (ST0_CU1 | ST0_FR)) == ST0_CU1) {
+               /*
+                * No MSA in guest, or FPU enabled and not in FR=1 mode,
+                * guest reserved instruction exception
+                */
+               er = kvm_mips_emulate_ri_exc(cause, opc, run, vcpu);
+       } else if (!(kvm_read_c0_guest_config5(cop0) & MIPS_CONF5_MSAEN)) {
+               /* MSA disabled by guest, guest MSA disabled exception */
+               er = kvm_mips_emulate_msadis_exc(cause, opc, run, vcpu);
+       } else {
+               /* Restore MSA/FPU state */
+               kvm_own_msa(vcpu);
+               er = EMULATE_DONE;
+       }
 
        switch (er) {
        case EMULATE_DONE:
@@ -608,6 +646,7 @@ static struct kvm_mips_callbacks kvm_trap_emul_callbacks = {
        .handle_res_inst = kvm_trap_emul_handle_res_inst,
        .handle_break = kvm_trap_emul_handle_break,
        .handle_trap = kvm_trap_emul_handle_trap,
+       .handle_msa_fpe = kvm_trap_emul_handle_msa_fpe,
        .handle_fpe = kvm_trap_emul_handle_fpe,
        .handle_msa_disabled = kvm_trap_emul_handle_msa_disabled,