[PATCH v1 1/2] s390x/kvm: Get rid of legacy_s390_alloc()

[David Hildenbrand <david@redhat.com>]

legacy_s390_alloc() was required for dealing with the absence of the ESOP
feature -- on old HW (< gen 10) and old z/VM versions (< 6.3).

As z/VM v6.2 (and even v6.3) is no longer supported since 2017 [1]
and we don't expect to have real users on such old hardware, let's drop
legacy_s390_alloc().

Still check+report an error just in case someone still runs on
such old z/VM environments, or someone runs under weird nested KVM
setups (where we can manually disable ESOP via the CPU model).

No need to check for KVM_CAP_GMAP - that should always be around on
kernels that also have KVM_CAP_DEVICE_CTRL (>= v3.15).

[1] https://www.ibm.com/support/lifecycle/search?q=z%2FVM

Suggested-by: Cornelia Huck <cohuck@redhat.com>
Suggested-by: Thomas Huth <thuth@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Halil Pasic <pasic@linux.ibm.com>
Cc: Cornelia Huck <cohuck@redhat.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Thomas Huth <thuth@redhat.com>
Cc: Igor Mammedov <imammedo@redhat.com>
Cc: Peter Xu <peterx@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
 target/s390x/kvm.c | 43 +++++--------------------------------------
 1 file changed, 5 insertions(+), 38 deletions(-)

diff --git a/target/s390x/kvm.c b/target/s390x/kvm.c
index 7a892d663d..84b40572f2 100644
--- a/target/s390x/kvm.c
+++ b/target/s390x/kvm.c
@@ -161,8 +161,6 @@ static int cap_protected;
 
 static int active_cmma;
 
-static void *legacy_s390_alloc(size_t size, uint64_t *align, bool shared);
-
 static int kvm_s390_query_mem_limit(uint64_t *memory_limit)
 {
     struct kvm_device_attr attr = {
@@ -349,6 +347,11 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
                      "please use kernel 3.15 or newer");
         return -1;
     }
+    if (!kvm_check_extension(s, KVM_CAP_S390_COW)) {
+        error_report("KVM is missing capability KVM_CAP_S390_COW - "
+                     "unsupported environment");
+        return -1;
+    }
 
     cap_sync_regs = kvm_check_extension(s, KVM_CAP_SYNC_REGS);
     cap_async_pf = kvm_check_extension(s, KVM_CAP_ASYNC_PF);
@@ -357,11 +360,6 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
     cap_vcpu_resets = kvm_check_extension(s, KVM_CAP_S390_VCPU_RESETS);
     cap_protected = kvm_check_extension(s, KVM_CAP_S390_PROTECTED);
 
-    if (!kvm_check_extension(s, KVM_CAP_S390_GMAP)
-        || !kvm_check_extension(s, KVM_CAP_S390_COW)) {
-        phys_mem_set_alloc(legacy_s390_alloc);
-    }
-
     kvm_vm_enable_cap(s, KVM_CAP_S390_USER_SIGP, 0);
     kvm_vm_enable_cap(s, KVM_CAP_S390_VECTOR_REGISTERS, 0);
     kvm_vm_enable_cap(s, KVM_CAP_S390_USER_STSI, 0);
@@ -889,37 +887,6 @@ int kvm_s390_mem_op_pv(S390CPU *cpu, uint64_t offset, void *hostbuf,
     return ret;
 }
 
-/*
- * Legacy layout for s390:
- * Older S390 KVM requires the topmost vma of the RAM to be
- * smaller than an system defined value, which is at least 256GB.
- * Larger systems have larger values. We put the guest between
- * the end of data segment (system break) and this value. We
- * use 32GB as a base to have enough room for the system break
- * to grow. We also have to use MAP parameters that avoid
- * read-only mapping of guest pages.
- */
-static void *legacy_s390_alloc(size_t size, uint64_t *align, bool shared)
-{
-    static void *mem;
-
-    if (mem) {
-        /* we only support one allocation, which is enough for initial ram */
-        return NULL;
-    }
-
-    mem = mmap((void *) 0x800000000ULL, size,
-               PROT_EXEC|PROT_READ|PROT_WRITE,
-               MAP_SHARED | MAP_ANONYMOUS | MAP_FIXED, -1, 0);
-    if (mem == MAP_FAILED) {
-        mem = NULL;
-    }
-    if (mem && align) {
-        *align = QEMU_VMALLOC_ALIGN;
-    }
-    return mem;
-}
-
 static uint8_t const *sw_bp_inst;
 static uint8_t sw_bp_ilen;
 
-- 
2.29.2