KVM: s390: Minor refactor of base/ext facility lists

Directly use the size of the arrays instead of going through the
indirection of kvm_s390_fac_size().
Don't use magic number for the number of entries in the non hypervisor
managed facility bit mask list.
Make the constraint of that number on kvm_s390_fac_base obvious.
Get rid of implicit double anding of stfle_fac_list.

Signed-off-by: Nina Schoetterl-Glausch <nsg@linux.ibm.com>
Co-developed-by: Christoph Schlameuss <schlameuss@linux.ibm.com>
Signed-off-by: Christoph Schlameuss <schlameuss@linux.ibm.com>
Reviewed-by: Janosch Frank <frankja@linux.ibm.com>
Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Message-ID: <20260612-vsie-alter-stfle-fac-v4-1-74f0e1559929@linux.ibm.com>

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index d503e4d0072a7a2c8202df94ab3d8e16aa1792fc..7334c160d0199162dced54b427e9cc168bc74b16 100644 (file)
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -237,33 +237,25 @@ static int async_destroy = 1;
 module_param(async_destroy, int, 0444);
 MODULE_PARM_DESC(async_destroy, "Asynchronous destroy for protected guests");
 
-/*
- * For now we handle at most 16 double words as this is what the s390 base
- * kernel handles and stores in the prefix page. If we ever need to go beyond
- * this, this requires changes to code, but the external uapi can stay.
- */
-#define SIZE_INTERNAL 16
-
+#define HMFAI_DWORDS 16
 /*
  * Base feature mask that defines default mask for facilities. Consists of the
  * defines in FACILITIES_KVM and the non-hypervisor managed bits.
  */
-static unsigned long kvm_s390_fac_base[SIZE_INTERNAL] = { FACILITIES_KVM };
+static unsigned long kvm_s390_fac_base[HMFAI_DWORDS] = { FACILITIES_KVM };
+static_assert(ARRAY_SIZE(((long[]){ FACILITIES_KVM })) <= HMFAI_DWORDS);
+static_assert(ARRAY_SIZE(kvm_s390_fac_base) <= S390_ARCH_FAC_MASK_SIZE_U64);
+static_assert(ARRAY_SIZE(kvm_s390_fac_base) <= S390_ARCH_FAC_LIST_SIZE_U64);
+static_assert(ARRAY_SIZE(kvm_s390_fac_base) <= ARRAY_SIZE(stfle_fac_list));
+
 /*
  * Extended feature mask. Consists of the defines in FACILITIES_KVM_CPUMODEL
  * and defines the facilities that can be enabled via a cpu model.
  */
-static unsigned long kvm_s390_fac_ext[SIZE_INTERNAL] = { FACILITIES_KVM_CPUMODEL };
-
-static unsigned long kvm_s390_fac_size(void)
-{
-       BUILD_BUG_ON(SIZE_INTERNAL > S390_ARCH_FAC_MASK_SIZE_U64);
-       BUILD_BUG_ON(SIZE_INTERNAL > S390_ARCH_FAC_LIST_SIZE_U64);
-       BUILD_BUG_ON(SIZE_INTERNAL * sizeof(unsigned long) >
-               sizeof(stfle_fac_list));
-
-       return SIZE_INTERNAL;
-}
+static const unsigned long kvm_s390_fac_ext[] = { FACILITIES_KVM_CPUMODEL };
+static_assert(ARRAY_SIZE(kvm_s390_fac_ext) <= S390_ARCH_FAC_MASK_SIZE_U64);
+static_assert(ARRAY_SIZE(kvm_s390_fac_ext) <= S390_ARCH_FAC_LIST_SIZE_U64);
+static_assert(ARRAY_SIZE(kvm_s390_fac_ext) <= ARRAY_SIZE(stfle_fac_list));
 
 /* available cpu features supported by kvm */
 static DECLARE_BITMAP(kvm_s390_available_cpu_feat, KVM_S390_VM_CPU_FEAT_NR_BITS);
@@ -3249,13 +3241,16 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
        kvm->arch.sie_page2->kvm = kvm;
        kvm->arch.model.fac_list = kvm->arch.sie_page2->fac_list;
 
-       for (i = 0; i < kvm_s390_fac_size(); i++) {
+       for (i = 0; i < ARRAY_SIZE(kvm_s390_fac_base); i++) {
                kvm->arch.model.fac_mask[i] = stfle_fac_list[i] &
-                                             (kvm_s390_fac_base[i] |
-                                              kvm_s390_fac_ext[i]);
+                                             kvm_s390_fac_base[i];
                kvm->arch.model.fac_list[i] = stfle_fac_list[i] &
                                              kvm_s390_fac_base[i];
        }
+       for (i = 0; i < ARRAY_SIZE(kvm_s390_fac_ext); i++) {
+               kvm->arch.model.fac_mask[i] |= stfle_fac_list[i] &
+                                              kvm_s390_fac_ext[i];
+       }
        kvm->arch.model.subfuncs = kvm_s390_available_subfunc;
 
        /* we are always in czam mode - even on pre z14 machines */
@@ -5878,9 +5873,8 @@ static int __init kvm_s390_init(void)
                pr_info("Disabling 2G hugepage support, since 1M hugepage support is not enabled.\n");
        }
 
-       for (i = 0; i < 16; i++)
-               kvm_s390_fac_base[i] |=
-                       stfle_fac_list[i] & nonhyp_mask(i);
+       for (i = 0; i < HMFAI_DWORDS; i++)
+               kvm_s390_fac_base[i] |= nonhyp_mask(i);
 
        r = __kvm_s390_init();
        if (r)