KVM: s390: Allow stfle instruction in the guest

2.6.31-rc introduced an architecture level set checker based on facility
bits. e.g. if the kernel is compiled to run only on z9, several facility
bits are checked very early and the kernel refuses to boot if a z9 specific
facility is missing.
Until now kvm on s390 did not implement the store facility extended (STFLE)
instruction. A 2.6.31-rc kernel that was compiled for z9 or higher did not
boot in kvm. This patch implements stfle.

This patch should go in before 2.6.31.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

3 files changed, 26 insertions, 3 deletions

diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
index a27d0d5a6f86..1cd02f6073a0 100644
--- a/arch/s390/include/asm/kvm_host.h
+++ b/arch/s390/include/asm/kvm_host.h
@@ -99,7 +99,9 @@ struct kvm_s390_sie_block {
         __u8    reservedd0[48];         /* 0x00d0 */
         __u64   gcr[16];                /* 0x0100 */
         __u64   gbea;                   /* 0x0180 */
-        __u8    reserved188[120];       /* 0x0188 */
+        __u8    reserved188[24];        /* 0x0188 */
+        __u32   fac;                    /* 0x01a0 */
+        __u8    reserved1a4[92];        /* 0x01a4 */
 } __attribute__((packed));
 
 struct kvm_vcpu_stat {
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index c18b21d6991c..90d9d1ba258b 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -25,6 +25,7 @@
 #include <asm/lowcore.h>
 #include <asm/pgtable.h>
 #include <asm/nmi.h>
+#include <asm/system.h>
 #include "kvm-s390.h"
 #include "gaccess.h"
 
@@ -69,6 +70,7 @@ struct kvm_stats_debugfs_item debugfs_entries[] = {
         { NULL }
 };
 
+static unsigned long long *facilities;
 
 /* Section: not file related */
 void kvm_arch_hardware_enable(void *garbage)
@@ -288,6 +290,7 @@ int kvm_arch_vcpu_setup(struct kvm_vcpu *vcpu)
         vcpu->arch.sie_block->gmsor = vcpu->kvm->arch.guest_origin;
         vcpu->arch.sie_block->ecb   = 2;
         vcpu->arch.sie_block->eca   = 0xC1002001U;
+        vcpu->arch.sie_block->fac   = (int) (long) facilities;
         hrtimer_init(&vcpu->arch.ckc_timer, CLOCK_REALTIME, HRTIMER_MODE_ABS);
         tasklet_init(&vcpu->arch.tasklet, kvm_s390_tasklet,
                      (unsigned long) vcpu);
@@ -739,11 +742,29 @@ gfn_t unalias_gfn(struct kvm *kvm, gfn_t gfn)
 
 static int __init kvm_s390_init(void)
 {
-        return kvm_init(NULL, sizeof(struct kvm_vcpu), THIS_MODULE);
+        int ret;
+        ret = kvm_init(NULL, sizeof(struct kvm_vcpu), THIS_MODULE);
+        if (ret)
+                return ret;
+
+        /*
+         * guests can ask for up to 255+1 double words, we need a full page
+         * to hold the maximum amount of facilites. On the other hand, we
+         * only set facilities that are known to work in KVM.
+         */
+        facilities = (unsigned long long *) get_zeroed_page(GFP_DMA);
+        if (!facilities) {
+                kvm_exit();
+                return -ENOMEM;
+        }
+        stfle(facilities, 1);
+        facilities[0] &= 0xff00fff3f0700000ULL;
+        return 0;
 }
 
 static void __exit kvm_s390_exit(void)
 {
+        free_page((unsigned long) facilities);
         kvm_exit();
 }
 
diff --git a/arch/s390/kvm/priv.c b/arch/s390/kvm/priv.c
index 93ecd06e1a74..d426aac8095d 100644
--- a/arch/s390/kvm/priv.c
+++ b/arch/s390/kvm/priv.c
@@ -158,7 +158,7 @@ static int handle_stfl(struct kvm_vcpu *vcpu)
 
         vcpu->stat.instruction_stfl++;
         /* only pass the facility bits, which we can handle */
-        facility_list &= 0xfe00fff3;
+        facility_list &= 0xff00fff3;
 
         rc = copy_to_guest(vcpu, offsetof(struct _lowcore, stfl_fac_list),
                            &facility_list, sizeof(facility_list));