KVM: s390: make exit_sie_sync more robust

exit_sie_sync is used to kick CPUs out of SIE and prevent reentering at
any point in time. This is used to reload the prefix pages and to
set the IBS stuff in a way that guarantees that after this function
returns we are no longer in SIE. All current users trigger KVM requests.

The request must be set before we block the CPUs to avoid races. Let's
make this implicit by adding the request into a new function
kvm_s390_sync_requests that replaces exit_sie_sync and split out
s390_vcpu_block and s390_vcpu_unblock, that can be used to keep
CPUs out of SIE independent of requests.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>

diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
index 1011ac1434f5c39dbbb81d1342b538adff93b90d..444c412307cbafc6b45ea557c1521c4e71f7d5ca 100644 (file)
--- a/arch/s390/include/asm/kvm_host.h
+++ b/arch/s390/include/asm/kvm_host.h
@@ -96,7 +96,8 @@ struct kvm_s390_sie_block {
 #define PROG_IN_SIE (1<<0)
        __u32   prog0c;                 /* 0x000c */
        __u8    reserved10[16];         /* 0x0010 */
-#define PROG_BLOCK_SIE 0x00000001
+#define PROG_BLOCK_SIE (1<<0)
+#define PROG_REQUEST   (1<<1)
        atomic_t prog20;                /* 0x0020 */
        __u8    reserved24[4];          /* 0x0024 */
        __u64   cputm;                  /* 0x0028 */

diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S
index 99b44acbfcc726b3035abc5046aaa4bb0f58fa1a..3238893c9d4ff66d492ce2a04421b85fa0cc0c34 100644 (file)
--- a/arch/s390/kernel/entry.S
+++ b/arch/s390/kernel/entry.S
@@ -1005,7 +1005,7 @@ ENTRY(sie64a)
 .Lsie_gmap:
        lg      %r14,__SF_EMPTY(%r15)           # get control block pointer
        oi      __SIE_PROG0C+3(%r14),1          # we are going into SIE now
-       tm      __SIE_PROG20+3(%r14),1          # last exit...
+       tm      __SIE_PROG20+3(%r14),3          # last exit...
        jnz     .Lsie_done
        LPP     __SF_EMPTY(%r15)                # set guest id
        sie     0(%r14)

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 142d9b40528db59d7fa35dff6754c2d2ddd0ca4a..9bc57afe54ba19fd8317bfd9d82b830ef2bfe169 100644 (file)
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -1424,6 +1424,16 @@ void s390_vcpu_unblock(struct kvm_vcpu *vcpu)
        atomic_clear_mask(PROG_BLOCK_SIE, &vcpu->arch.sie_block->prog20);
 }
 
+static void kvm_s390_vcpu_request(struct kvm_vcpu *vcpu)
+{
+       atomic_set_mask(PROG_REQUEST, &vcpu->arch.sie_block->prog20);
+}
+
+static void kvm_s390_vcpu_request_handled(struct kvm_vcpu *vcpu)
+{
+       atomic_clear_mask(PROG_REQUEST, &vcpu->arch.sie_block->prog20);
+}
+
 /*
  * Kick a guest cpu out of SIE and wait until SIE is not running.
  * If the CPU is not running (e.g. waiting as idle) the function will
@@ -1435,10 +1445,11 @@ void exit_sie(struct kvm_vcpu *vcpu)
                cpu_relax();
 }
 
-/* Kick a guest cpu out of SIE and prevent SIE-reentry */
-void exit_sie_sync(struct kvm_vcpu *vcpu)
+/* Kick a guest cpu out of SIE to process a request synchronously */
+void kvm_s390_sync_request(int req, struct kvm_vcpu *vcpu)
 {
-       s390_vcpu_block(vcpu);
+       kvm_make_request(req, vcpu);
+       kvm_s390_vcpu_request(vcpu);
        exit_sie(vcpu);
 }
 
@@ -1452,8 +1463,7 @@ static void kvm_gmap_notifier(struct gmap *gmap, unsigned long address)
                /* match against both prefix pages */
                if (kvm_s390_get_prefix(vcpu) == (address & ~0x1000UL)) {
                        VCPU_EVENT(vcpu, 2, "gmap notifier for %lx", address);
-                       kvm_make_request(KVM_REQ_MMU_RELOAD, vcpu);
-                       exit_sie_sync(vcpu);
+                       kvm_s390_sync_request(KVM_REQ_MMU_RELOAD, vcpu);
                }
        }
 }
@@ -1728,7 +1738,7 @@ static int kvm_s390_handle_requests(struct kvm_vcpu *vcpu)
        if (!vcpu->requests)
                return 0;
 retry:
-       s390_vcpu_unblock(vcpu);
+       kvm_s390_vcpu_request_handled(vcpu);
        /*
         * We use MMU_RELOAD just to re-arm the ipte notifier for the
         * guest prefix page. gmap_ipte_notify will wait on the ptl lock.
@@ -2213,8 +2223,7 @@ int kvm_s390_vcpu_store_adtl_status(struct kvm_vcpu *vcpu, unsigned long addr)
 static void __disable_ibs_on_vcpu(struct kvm_vcpu *vcpu)
 {
        kvm_check_request(KVM_REQ_ENABLE_IBS, vcpu);
-       kvm_make_request(KVM_REQ_DISABLE_IBS, vcpu);
-       exit_sie_sync(vcpu);
+       kvm_s390_sync_request(KVM_REQ_DISABLE_IBS, vcpu);
 }
 
 static void __disable_ibs_on_all_vcpus(struct kvm *kvm)
@@ -2230,8 +2239,7 @@ static void __disable_ibs_on_all_vcpus(struct kvm *kvm)
 static void __enable_ibs_on_vcpu(struct kvm_vcpu *vcpu)
 {
        kvm_check_request(KVM_REQ_DISABLE_IBS, vcpu);
-       kvm_make_request(KVM_REQ_ENABLE_IBS, vcpu);
-       exit_sie_sync(vcpu);
+       kvm_s390_sync_request(KVM_REQ_ENABLE_IBS, vcpu);
 }
 
 void kvm_s390_vcpu_start(struct kvm_vcpu *vcpu)

diff --git a/arch/s390/kvm/kvm-s390.h b/arch/s390/kvm/kvm-s390.h
index ca108b90ae5613a15e0d82a68ef0288a93d62792..8edca85e246ed4bcc39d8721ae6d5ea1279655e7 100644 (file)
--- a/arch/s390/kvm/kvm-s390.h
+++ b/arch/s390/kvm/kvm-s390.h
@@ -214,7 +214,7 @@ void kvm_s390_vcpu_stop(struct kvm_vcpu *vcpu);
 void s390_vcpu_block(struct kvm_vcpu *vcpu);
 void s390_vcpu_unblock(struct kvm_vcpu *vcpu);
 void exit_sie(struct kvm_vcpu *vcpu);
-void exit_sie_sync(struct kvm_vcpu *vcpu);
+void kvm_s390_sync_request(int req, struct kvm_vcpu *vcpu);
 int kvm_s390_vcpu_setup_cmma(struct kvm_vcpu *vcpu);
 void kvm_s390_vcpu_unsetup_cmma(struct kvm_vcpu *vcpu);
 /* is cmma enabled */