KVM: s390: Support keyless subset guest mode

If the KSS facility is available on the machine, we also make it
available for our KVM guests.

The KSS facility bypasses storage key management as long as the guest
does not issue a related instruction. When that happens, the control is
returned to the host, which has to turn off KSS for a guest vcpu
before retrying the instruction.

Signed-off-by: Corey S. McQuay <csmcquay@linux.vnet.ibm.com>
Signed-off-by: Farhan Ali <alifm@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>

diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
index 552c319483c63d17fa0b16c8ece38d12623ee884..426614a882a9b12a71c96f06607f30e6b345cd0d 100644 (file)
--- a/arch/s390/include/asm/kvm_host.h
+++ b/arch/s390/include/asm/kvm_host.h
@@ -122,6 +122,7 @@ struct esca_block {
 #define CPUSTAT_SLSR       0x00002000
 #define CPUSTAT_ZARCH      0x00000800
 #define CPUSTAT_MCDS       0x00000100
+#define CPUSTAT_KSS        0x00000200
 #define CPUSTAT_SM         0x00000080
 #define CPUSTAT_IBS        0x00000040
 #define CPUSTAT_GED2       0x00000010
@@ -185,6 +186,7 @@ struct kvm_s390_sie_block {
 #define ICPT_OPEREXC   0x2C
 #define ICPT_PARTEXEC  0x38
 #define ICPT_IOINST    0x40
+#define ICPT_KSS       0x5c
        __u8    icptcode;               /* 0x0050 */
        __u8    icptstatus;             /* 0x0051 */
        __u16   ihcpu;                  /* 0x0052 */

diff --git a/arch/s390/include/uapi/asm/kvm.h b/arch/s390/include/uapi/asm/kvm.h
index 2c9ad251fa3381286239443e41f1893eb1b631e4..bf9267930939fefd79422d08776a205acf71f1a7 100644 (file)
--- a/arch/s390/include/uapi/asm/kvm.h
+++ b/arch/s390/include/uapi/asm/kvm.h
@@ -119,6 +119,7 @@ struct kvm_s390_vm_cpu_machine {
 #define KVM_S390_VM_CPU_FEAT_CMMA      10
 #define KVM_S390_VM_CPU_FEAT_PFMFI     11
 #define KVM_S390_VM_CPU_FEAT_SIGPIF    12
+#define KVM_S390_VM_CPU_FEAT_KSS       13
 struct kvm_s390_vm_cpu_feat {
        __u64 feat[16];
 };

diff --git a/arch/s390/kvm/intercept.c b/arch/s390/kvm/intercept.c
index f5378f3361273bc19b0f84148f2a599d9f98bbac..a4752bf6b526d0e45164ed146931a2d0ea177706 100644 (file)
--- a/arch/s390/kvm/intercept.c
+++ b/arch/s390/kvm/intercept.c
@@ -426,6 +426,9 @@ int kvm_handle_sie_intercept(struct kvm_vcpu *vcpu)
        case ICPT_PARTEXEC:
                rc = handle_partial_execution(vcpu);
                break;
+       case ICPT_KSS:
+               rc = kvm_s390_skey_check_enable(vcpu);
+               break;
        default:
                return -EOPNOTSUPP;
        }

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 11b7d66389916bbb8d2d2474143ead5e9b7caa27..8771fef112a1be41a2d01c395370dc9de9ffc314 100644 (file)
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -300,6 +300,8 @@ static void kvm_s390_cpu_feat_init(void)
                allow_cpu_feat(KVM_S390_VM_CPU_FEAT_CEI);
        if (sclp.has_ibs)
                allow_cpu_feat(KVM_S390_VM_CPU_FEAT_IBS);
+       if (sclp.has_kss)
+               allow_cpu_feat(KVM_S390_VM_CPU_FEAT_KSS);
        /*
         * KVM_S390_VM_CPU_FEAT_SKEY: Wrong shadow of PTE.I bits will make
         * all skey handling functions read/set the skey from the PGSTE
@@ -2034,7 +2036,11 @@ int kvm_arch_vcpu_setup(struct kvm_vcpu *vcpu)
        vcpu->arch.sie_block->sdnxo = ((unsigned long) &vcpu->run->s.regs.sdnx)
                                        | SDNXC;
        vcpu->arch.sie_block->riccbd = (unsigned long) &vcpu->run->s.regs.riccb;
-       vcpu->arch.sie_block->ictl |= ICTL_ISKE | ICTL_SSKE | ICTL_RRBE;
+
+       if (sclp.has_kss)
+               atomic_or(CPUSTAT_KSS, &vcpu->arch.sie_block->cpuflags);
+       else
+               vcpu->arch.sie_block->ictl |= ICTL_ISKE | ICTL_SSKE | ICTL_RRBE;
 
        if (vcpu->kvm->arch.use_cmma) {
                rc = kvm_s390_vcpu_setup_cmma(vcpu);

diff --git a/arch/s390/kvm/kvm-s390.h b/arch/s390/kvm/kvm-s390.h
index 455124fe06476c66dcaa7620a6bbaa4e29144303..55f5c8457d6d461ff9a3eb8cdc508f4d83055fbb 100644 (file)
--- a/arch/s390/kvm/kvm-s390.h
+++ b/arch/s390/kvm/kvm-s390.h
@@ -254,6 +254,7 @@ int kvm_s390_handle_lpsw(struct kvm_vcpu *vcpu);
 int kvm_s390_handle_stctl(struct kvm_vcpu *vcpu);
 int kvm_s390_handle_lctl(struct kvm_vcpu *vcpu);
 int kvm_s390_handle_eb(struct kvm_vcpu *vcpu);
+int kvm_s390_skey_check_enable(struct kvm_vcpu *vcpu);
 
 /* implemented in vsie.c */
 int kvm_s390_handle_vsie(struct kvm_vcpu *vcpu);

diff --git a/arch/s390/kvm/priv.c b/arch/s390/kvm/priv.c
index 0ffe973535fab86194818cc5a86b8c1de084b1cb..c03106c428cfa89e1f25297efbd2d667a73b5fd7 100644 (file)
--- a/arch/s390/kvm/priv.c
+++ b/arch/s390/kvm/priv.c
@@ -198,18 +198,25 @@ static int handle_store_cpu_address(struct kvm_vcpu *vcpu)
        return 0;
 }
 
-static int __skey_check_enable(struct kvm_vcpu *vcpu)
+int kvm_s390_skey_check_enable(struct kvm_vcpu *vcpu)
 {
        int rc = 0;
+       struct kvm_s390_sie_block *sie_block = vcpu->arch.sie_block;
 
        trace_kvm_s390_skey_related_inst(vcpu);
-       if (!(vcpu->arch.sie_block->ictl & (ICTL_ISKE | ICTL_SSKE | ICTL_RRBE)))
+       if (!(sie_block->ictl & (ICTL_ISKE | ICTL_SSKE | ICTL_RRBE)) &&
+           !(atomic_read(&sie_block->cpuflags) & CPUSTAT_KSS))
                return rc;
 
        rc = s390_enable_skey();
        VCPU_EVENT(vcpu, 3, "enabling storage keys for guest: %d", rc);
-       if (!rc)
-               vcpu->arch.sie_block->ictl &= ~(ICTL_ISKE | ICTL_SSKE | ICTL_RRBE);
+       if (!rc) {
+               if (atomic_read(&sie_block->cpuflags) & CPUSTAT_KSS)
+                       atomic_andnot(CPUSTAT_KSS, &sie_block->cpuflags);
+               else
+                       sie_block->ictl &= ~(ICTL_ISKE | ICTL_SSKE |
+                                            ICTL_RRBE);
+       }
        return rc;
 }
 
@@ -218,7 +225,7 @@ static int try_handle_skey(struct kvm_vcpu *vcpu)
        int rc;
 
        vcpu->stat.instruction_storage_key++;
-       rc = __skey_check_enable(vcpu);
+       rc = kvm_s390_skey_check_enable(vcpu);
        if (rc)
                return rc;
        if (sclp.has_skey) {
@@ -916,7 +923,7 @@ static int handle_pfmf(struct kvm_vcpu *vcpu)
                }
 
                if (vcpu->run->s.regs.gprs[reg1] & PFMF_SK) {
-                       int rc = __skey_check_enable(vcpu);
+                       int rc = kvm_s390_skey_check_enable(vcpu);
 
                        if (rc)
                                return rc;

diff --git a/arch/s390/kvm/vsie.c b/arch/s390/kvm/vsie.c
index 025b1f2e17a9d45229cafea09cfb9122807d6a8f..4719ecb9ab423b7a3c0cc246c0baa856cdd10544 100644 (file)
--- a/arch/s390/kvm/vsie.c
+++ b/arch/s390/kvm/vsie.c
@@ -117,6 +117,8 @@ static int prepare_cpuflags(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
                newflags |= cpuflags & CPUSTAT_SM;
        if (test_kvm_cpu_feat(vcpu->kvm, KVM_S390_VM_CPU_FEAT_IBS))
                newflags |= cpuflags & CPUSTAT_IBS;
+       if (test_kvm_cpu_feat(vcpu->kvm, KVM_S390_VM_CPU_FEAT_KSS))
+               newflags |= cpuflags & CPUSTAT_KSS;
 
        atomic_set(&scb_s->cpuflags, newflags);
        return 0;
@@ -289,7 +291,9 @@ static int shadow_scb(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
         * bits. Therefore we cannot provide interpretation and would later
         * have to provide own emulation handlers.
         */
-       scb_s->ictl |= ICTL_ISKE | ICTL_SSKE | ICTL_RRBE;
+       if (!(atomic_read(&scb_s->cpuflags) & CPUSTAT_KSS))
+               scb_s->ictl |= ICTL_ISKE | ICTL_SSKE | ICTL_RRBE;
+
        scb_s->icpua = scb_o->icpua;
 
        if (!(atomic_read(&scb_s->cpuflags) & CPUSTAT_SM))