s390/kvm: remove explicit -EFAULT return code checking on guest access

Let's change to the paradigm that every return code from guest memory
access functions that is not zero translates to -EFAULT and do not
explictly compare.
Explictly comparing the return value with -EFAULT has already shown to
be a bit fragile. In addition this is closer to the handling of
copy_to/from_user functions, which imho is in general a good idea.

Also shorten the return code handling in interrupt.c a bit.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

3 files changed, 74 insertions, 177 deletions

diff --git a/arch/s390/kvm/intercept.c b/arch/s390/kvm/intercept.c
index f26ff1e31bdb..9b2204759445 100644
--- a/arch/s390/kvm/intercept.c
+++ b/arch/s390/kvm/intercept.c
@@ -45,7 +45,7 @@ static int handle_lctlg(struct kvm_vcpu *vcpu)
         do {
                 rc = get_guest_u64(vcpu, useraddr,
                                    &vcpu->arch.sie_block->gcr[reg]);
-                if (rc == -EFAULT) {
+                if (rc) {
                         kvm_s390_inject_program_int(vcpu, PGM_ADDRESSING);
                         break;
                 }
@@ -79,7 +79,7 @@ static int handle_lctl(struct kvm_vcpu *vcpu)
         reg = reg1;
         do {
                 rc = get_guest_u32(vcpu, useraddr, &val);
-                if (rc == -EFAULT) {
+                if (rc) {
                         kvm_s390_inject_program_int(vcpu, PGM_ADDRESSING);
                         break;
                 }
diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
index 37116a77cb4b..5afa931aed11 100644
--- a/arch/s390/kvm/interrupt.c
+++ b/arch/s390/kvm/interrupt.c
@@ -180,7 +180,7 @@ static void __do_deliver_interrupt(struct kvm_vcpu *vcpu,
                                    struct kvm_s390_interrupt_info *inti)
 {
         const unsigned short table[] = { 2, 4, 4, 6 };
-        int rc, exception = 0;
+        int rc = 0;
 
         switch (inti->type) {
         case KVM_S390_INT_EMERGENCY:
@@ -188,74 +188,38 @@ static void __do_deliver_interrupt(struct kvm_vcpu *vcpu,
                 vcpu->stat.deliver_emergency_signal++;
                 trace_kvm_s390_deliver_interrupt(vcpu->vcpu_id, inti->type,
                                                  inti->emerg.code, 0);
-                rc = put_guest_u16(vcpu, __LC_EXT_INT_CODE, 0x1201);
-                if (rc == -EFAULT)
-                        exception = 1;
-
-                rc = put_guest_u16(vcpu, __LC_EXT_CPU_ADDR, inti->emerg.code);
-                if (rc == -EFAULT)
-                        exception = 1;
-
-                rc = copy_to_guest(vcpu, __LC_EXT_OLD_PSW,
-                         &vcpu->arch.sie_block->gpsw, sizeof(psw_t));
-                if (rc == -EFAULT)
-                        exception = 1;
-
-                rc = copy_from_guest(vcpu, &vcpu->arch.sie_block->gpsw,
-                        __LC_EXT_NEW_PSW, sizeof(psw_t));
-                if (rc == -EFAULT)
-                        exception = 1;
+                rc  = put_guest_u16(vcpu, __LC_EXT_INT_CODE, 0x1201);
+                rc |= put_guest_u16(vcpu, __LC_EXT_CPU_ADDR, inti->emerg.code);
+                rc |= copy_to_guest(vcpu, __LC_EXT_OLD_PSW,
+                                    &vcpu->arch.sie_block->gpsw, sizeof(psw_t));
+                rc |= copy_from_guest(vcpu, &vcpu->arch.sie_block->gpsw,
+                                      __LC_EXT_NEW_PSW, sizeof(psw_t));
                 break;
-
         case KVM_S390_INT_EXTERNAL_CALL:
                 VCPU_EVENT(vcpu, 4, "%s", "interrupt: sigp ext call");
                 vcpu->stat.deliver_external_call++;
                 trace_kvm_s390_deliver_interrupt(vcpu->vcpu_id, inti->type,
                                                  inti->extcall.code, 0);
-                rc = put_guest_u16(vcpu, __LC_EXT_INT_CODE, 0x1202);
-                if (rc == -EFAULT)
-                        exception = 1;
-
-                rc = put_guest_u16(vcpu, __LC_EXT_CPU_ADDR, inti->extcall.code);
-                if (rc == -EFAULT)
-                        exception = 1;
-
-                rc = copy_to_guest(vcpu, __LC_EXT_OLD_PSW,
-                         &vcpu->arch.sie_block->gpsw, sizeof(psw_t));
-                if (rc == -EFAULT)
-                        exception = 1;
-
-                rc = copy_from_guest(vcpu, &vcpu->arch.sie_block->gpsw,
-                        __LC_EXT_NEW_PSW, sizeof(psw_t));
-                if (rc == -EFAULT)
-                        exception = 1;
+                rc  = put_guest_u16(vcpu, __LC_EXT_INT_CODE, 0x1202);
+                rc |= put_guest_u16(vcpu, __LC_EXT_CPU_ADDR, inti->extcall.code);
+                rc |= copy_to_guest(vcpu, __LC_EXT_OLD_PSW,
+                                    &vcpu->arch.sie_block->gpsw, sizeof(psw_t));
+                rc |= copy_from_guest(vcpu, &vcpu->arch.sie_block->gpsw,
+                                      __LC_EXT_NEW_PSW, sizeof(psw_t));
                 break;
-
         case KVM_S390_INT_SERVICE:
                 VCPU_EVENT(vcpu, 4, "interrupt: sclp parm:%x",
                            inti->ext.ext_params);
                 vcpu->stat.deliver_service_signal++;
                 trace_kvm_s390_deliver_interrupt(vcpu->vcpu_id, inti->type,
                                                  inti->ext.ext_params, 0);
-                rc = put_guest_u16(vcpu, __LC_EXT_INT_CODE, 0x2401);
-                if (rc == -EFAULT)
-                        exception = 1;
-
-                rc = copy_to_guest(vcpu, __LC_EXT_OLD_PSW,
-                         &vcpu->arch.sie_block->gpsw, sizeof(psw_t));
-                if (rc == -EFAULT)
-                        exception = 1;
-
-                rc = copy_from_guest(vcpu, &vcpu->arch.sie_block->gpsw,
-                        __LC_EXT_NEW_PSW, sizeof(psw_t));
-                if (rc == -EFAULT)
-                        exception = 1;
-
-                rc = put_guest_u32(vcpu, __LC_EXT_PARAMS, inti->ext.ext_params);
-                if (rc == -EFAULT)
-                        exception = 1;
+                rc  = put_guest_u16(vcpu, __LC_EXT_INT_CODE, 0x2401);
+                rc |= copy_to_guest(vcpu, __LC_EXT_OLD_PSW,
+                                    &vcpu->arch.sie_block->gpsw, sizeof(psw_t));
+                rc |= copy_from_guest(vcpu, &vcpu->arch.sie_block->gpsw,
+                                      __LC_EXT_NEW_PSW, sizeof(psw_t));
+                rc |= put_guest_u32(vcpu, __LC_EXT_PARAMS, inti->ext.ext_params);
                 break;
-
         case KVM_S390_INT_VIRTIO:
                 VCPU_EVENT(vcpu, 4, "interrupt: virtio parm:%x,parm64:%llx",
                            inti->ext.ext_params, inti->ext.ext_params2);
@@ -263,34 +227,16 @@ static void __do_deliver_interrupt(struct kvm_vcpu *vcpu,
                 trace_kvm_s390_deliver_interrupt(vcpu->vcpu_id, inti->type,
                                                  inti->ext.ext_params,
                                                  inti->ext.ext_params2);
-                rc = put_guest_u16(vcpu, __LC_EXT_INT_CODE, 0x2603);
-                if (rc == -EFAULT)
-                        exception = 1;
-
-                rc = put_guest_u16(vcpu, __LC_EXT_CPU_ADDR, 0x0d00);
-                if (rc == -EFAULT)
-                        exception = 1;
-
-                rc = copy_to_guest(vcpu, __LC_EXT_OLD_PSW,
-                         &vcpu->arch.sie_block->gpsw, sizeof(psw_t));
-                if (rc == -EFAULT)
-                        exception = 1;
-
-                rc = copy_from_guest(vcpu, &vcpu->arch.sie_block->gpsw,
-                        __LC_EXT_NEW_PSW, sizeof(psw_t));
-                if (rc == -EFAULT)
-                        exception = 1;
-
-                rc = put_guest_u32(vcpu, __LC_EXT_PARAMS, inti->ext.ext_params);
-                if (rc == -EFAULT)
-                        exception = 1;
-
-                rc = put_guest_u64(vcpu, __LC_EXT_PARAMS2,
-                                   inti->ext.ext_params2);
-                if (rc == -EFAULT)
-                        exception = 1;
+                rc  = put_guest_u16(vcpu, __LC_EXT_INT_CODE, 0x2603);
+                rc |= put_guest_u16(vcpu, __LC_EXT_CPU_ADDR, 0x0d00);
+                rc |= copy_to_guest(vcpu, __LC_EXT_OLD_PSW,
+                                    &vcpu->arch.sie_block->gpsw, sizeof(psw_t));
+                rc |= copy_from_guest(vcpu, &vcpu->arch.sie_block->gpsw,
+                                      __LC_EXT_NEW_PSW, sizeof(psw_t));
+                rc |= put_guest_u32(vcpu, __LC_EXT_PARAMS, inti->ext.ext_params);
+                rc |= put_guest_u64(vcpu, __LC_EXT_PARAMS2,
+                                    inti->ext.ext_params2);
                 break;
-
         case KVM_S390_SIGP_STOP:
                 VCPU_EVENT(vcpu, 4, "%s", "interrupt: cpu stop");
                 vcpu->stat.deliver_stop_signal++;
@@ -313,18 +259,14 @@ static void __do_deliver_interrupt(struct kvm_vcpu *vcpu,
                 vcpu->stat.deliver_restart_signal++;
                 trace_kvm_s390_deliver_interrupt(vcpu->vcpu_id, inti->type,
                                                  0, 0);
-                rc = copy_to_guest(vcpu, offsetof(struct _lowcore,
-                  restart_old_psw), &vcpu->arch.sie_block->gpsw, sizeof(psw_t));
-                if (rc == -EFAULT)
-                        exception = 1;
-
-                rc = copy_from_guest(vcpu, &vcpu->arch.sie_block->gpsw,
-                        offsetof(struct _lowcore, restart_psw), sizeof(psw_t));
-                if (rc == -EFAULT)
-                        exception = 1;
+                rc  = copy_to_guest(vcpu,
+                                    offsetof(struct _lowcore, restart_old_psw),
+                                    &vcpu->arch.sie_block->gpsw, sizeof(psw_t));
+                rc |= copy_from_guest(vcpu, &vcpu->arch.sie_block->gpsw,
+                                      offsetof(struct _lowcore, restart_psw),
+                                      sizeof(psw_t));
                 atomic_clear_mask(CPUSTAT_STOPPED, &vcpu->arch.sie_block->cpuflags);
                 break;
-
         case KVM_S390_PROGRAM_INT:
                 VCPU_EVENT(vcpu, 4, "interrupt: pgm check code:%x, ilc:%x",
                            inti->pgm.code,
@@ -332,24 +274,13 @@ static void __do_deliver_interrupt(struct kvm_vcpu *vcpu,
                 vcpu->stat.deliver_program_int++;
                 trace_kvm_s390_deliver_interrupt(vcpu->vcpu_id, inti->type,
                                                  inti->pgm.code, 0);
-                rc = put_guest_u16(vcpu, __LC_PGM_INT_CODE, inti->pgm.code);
-                if (rc == -EFAULT)
-                        exception = 1;
-
-                rc = put_guest_u16(vcpu, __LC_PGM_ILC,
-                        table[vcpu->arch.sie_block->ipa >> 14]);
-                if (rc == -EFAULT)
-                        exception = 1;
-
-                rc = copy_to_guest(vcpu, __LC_PGM_OLD_PSW,
-                         &vcpu->arch.sie_block->gpsw, sizeof(psw_t));
-                if (rc == -EFAULT)
-                        exception = 1;
-
-                rc = copy_from_guest(vcpu, &vcpu->arch.sie_block->gpsw,
-                        __LC_PGM_NEW_PSW, sizeof(psw_t));
-                if (rc == -EFAULT)
-                        exception = 1;
+                rc  = put_guest_u16(vcpu, __LC_PGM_INT_CODE, inti->pgm.code);
+                rc |= put_guest_u16(vcpu, __LC_PGM_ILC,
+                                    table[vcpu->arch.sie_block->ipa >> 14]);
+                rc |= copy_to_guest(vcpu, __LC_PGM_OLD_PSW,
+                                    &vcpu->arch.sie_block->gpsw, sizeof(psw_t));
+                rc |= copy_from_guest(vcpu, &vcpu->arch.sie_block->gpsw,
+                                      __LC_PGM_NEW_PSW, sizeof(psw_t));
                 break;
 
         case KVM_S390_MCHK:
@@ -358,24 +289,13 @@ static void __do_deliver_interrupt(struct kvm_vcpu *vcpu,
                 trace_kvm_s390_deliver_interrupt(vcpu->vcpu_id, inti->type,
                                                  inti->mchk.cr14,
                                                  inti->mchk.mcic);
-                rc = kvm_s390_vcpu_store_status(vcpu,
-                                                KVM_S390_STORE_STATUS_PREFIXED);
-                if (rc == -EFAULT)
-                        exception = 1;
-
-                rc = put_guest_u64(vcpu, __LC_MCCK_CODE, inti->mchk.mcic);
-                if (rc == -EFAULT)
-                        exception = 1;
-
-                rc = copy_to_guest(vcpu, __LC_MCK_OLD_PSW,
-                                   &vcpu->arch.sie_block->gpsw, sizeof(psw_t));
-                if (rc == -EFAULT)
-                        exception = 1;
-
-                rc = copy_from_guest(vcpu, &vcpu->arch.sie_block->gpsw,
-                                     __LC_MCK_NEW_PSW, sizeof(psw_t));
-                if (rc == -EFAULT)
-                        exception = 1;
+                rc  = kvm_s390_vcpu_store_status(vcpu,
+                                                 KVM_S390_STORE_STATUS_PREFIXED);
+                rc |= put_guest_u64(vcpu, __LC_MCCK_CODE, inti->mchk.mcic);
+                rc |= copy_to_guest(vcpu, __LC_MCK_OLD_PSW,
+                                    &vcpu->arch.sie_block->gpsw, sizeof(psw_t));
+                rc |= copy_from_guest(vcpu, &vcpu->arch.sie_block->gpsw,
+                                      __LC_MCK_NEW_PSW, sizeof(psw_t));
                 break;
 
         case KVM_S390_INT_IO_MIN...KVM_S390_INT_IO_MAX:
@@ -388,67 +308,44 @@ static void __do_deliver_interrupt(struct kvm_vcpu *vcpu,
                 vcpu->stat.deliver_io_int++;
                 trace_kvm_s390_deliver_interrupt(vcpu->vcpu_id, inti->type,
                                                  param0, param1);
-                rc = put_guest_u16(vcpu, __LC_SUBCHANNEL_ID,
-                                   inti->io.subchannel_id);
-                if (rc == -EFAULT)
-                        exception = 1;
-
-                rc = put_guest_u16(vcpu, __LC_SUBCHANNEL_NR,
-                                   inti->io.subchannel_nr);
-                if (rc == -EFAULT)
-                        exception = 1;
-
-                rc = put_guest_u32(vcpu, __LC_IO_INT_PARM,
-                                   inti->io.io_int_parm);
-                if (rc == -EFAULT)
-                        exception = 1;
-
-                rc = put_guest_u32(vcpu, __LC_IO_INT_WORD,
-                                   inti->io.io_int_word);
-                if (rc == -EFAULT)
-                        exception = 1;
-
-                rc = copy_to_guest(vcpu, __LC_IO_OLD_PSW,
-                                   &vcpu->arch.sie_block->gpsw, sizeof(psw_t));
-                if (rc == -EFAULT)
-                        exception = 1;
-
-                rc = copy_from_guest(vcpu, &vcpu->arch.sie_block->gpsw,
-                                     __LC_IO_NEW_PSW, sizeof(psw_t));
-                if (rc == -EFAULT)
-                        exception = 1;
+                rc  = put_guest_u16(vcpu, __LC_SUBCHANNEL_ID,
+                                    inti->io.subchannel_id);
+                rc |= put_guest_u16(vcpu, __LC_SUBCHANNEL_NR,
+                                    inti->io.subchannel_nr);
+                rc |= put_guest_u32(vcpu, __LC_IO_INT_PARM,
+                                    inti->io.io_int_parm);
+                rc |= put_guest_u32(vcpu, __LC_IO_INT_WORD,
+                                    inti->io.io_int_word);
+                rc |= copy_to_guest(vcpu, __LC_IO_OLD_PSW,
+                                    &vcpu->arch.sie_block->gpsw, sizeof(psw_t));
+                rc |= copy_from_guest(vcpu, &vcpu->arch.sie_block->gpsw,
+                                      __LC_IO_NEW_PSW, sizeof(psw_t));
                 break;
         }
         default:
                 BUG();
         }
-        if (exception) {
+        if (rc) {
                 printk("kvm: The guest lowcore is not mapped during interrupt "
-                        "delivery, killing userspace\n");
+                       "delivery, killing userspace\n");
                 do_exit(SIGKILL);
         }
 }
 
 static int __try_deliver_ckc_interrupt(struct kvm_vcpu *vcpu)
 {
-        int rc, exception = 0;
+        int rc;
 
         if (psw_extint_disabled(vcpu))
                 return 0;
         if (!(vcpu->arch.sie_block->gcr[0] & 0x800ul))
                 return 0;
-        rc = put_guest_u16(vcpu, __LC_EXT_INT_CODE, 0x1004);
-        if (rc == -EFAULT)
-                exception = 1;
-        rc = copy_to_guest(vcpu, __LC_EXT_OLD_PSW,
-                 &vcpu->arch.sie_block->gpsw, sizeof(psw_t));
-        if (rc == -EFAULT)
-                exception = 1;
-        rc = copy_from_guest(vcpu, &vcpu->arch.sie_block->gpsw,
-                __LC_EXT_NEW_PSW, sizeof(psw_t));
-        if (rc == -EFAULT)
-                exception = 1;
-        if (exception) {
+        rc  = put_guest_u16(vcpu, __LC_EXT_INT_CODE, 0x1004);
+        rc |= copy_to_guest(vcpu, __LC_EXT_OLD_PSW,
+                            &vcpu->arch.sie_block->gpsw, sizeof(psw_t));
+        rc |= copy_from_guest(vcpu, &vcpu->arch.sie_block->gpsw,
+                              __LC_EXT_NEW_PSW, sizeof(psw_t));
+        if (rc) {
                 printk("kvm: The guest lowcore is not mapped during interrupt "
                         "delivery, killing userspace\n");
                 do_exit(SIGKILL);
diff --git a/arch/s390/kvm/priv.c b/arch/s390/kvm/priv.c
index 75ad91e38e8a..34b42dc285ee 100644
--- a/arch/s390/kvm/priv.c
+++ b/arch/s390/kvm/priv.c
@@ -108,7 +108,7 @@ static int handle_store_cpu_address(struct kvm_vcpu *vcpu)
         }
 
         rc = put_guest_u16(vcpu, useraddr, vcpu->vcpu_id);
-        if (rc == -EFAULT) {
+        if (rc) {
                 kvm_s390_inject_program_int(vcpu, PGM_ADDRESSING);
                 goto out;
         }
@@ -230,7 +230,7 @@ static int handle_stfl(struct kvm_vcpu *vcpu)
 
         rc = copy_to_guest(vcpu, offsetof(struct _lowcore, stfl_fac_list),
                            &facility_list, sizeof(facility_list));
-        if (rc == -EFAULT)
+        if (rc)
                 kvm_s390_inject_program_int(vcpu, PGM_ADDRESSING);
         else {
                 VCPU_EVENT(vcpu, 5, "store facility list value %x",
@@ -348,7 +348,7 @@ static int handle_stidp(struct kvm_vcpu *vcpu)
         }
 
         rc = put_guest_u64(vcpu, operand2, vcpu->arch.stidp_data);
-        if (rc == -EFAULT) {
+        if (rc) {
                 kvm_s390_inject_program_int(vcpu, PGM_ADDRESSING);
                 goto out;
         }