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[Qemu-devel] [PATCH] target/s390x/kvm: Fix problem when running with SEL

From: Thomas Huth
Subject: [Qemu-devel] [PATCH] target/s390x/kvm: Fix problem when running with SELinux under z/VM
Date: Fri, 24 Mar 2017 10:26:55 +0100

When running QEMU with KVM under z/VM, the memory for the guest
is allocated via legacy_s390_alloc() since the KVM_CAP_S390_COW
extension is not supported on z/VM. legacy_s390_alloc() then uses
mmap(... PROT_EXEC ...) for the guest memory - but this does not
work when running with SELinux enabled, mmap() fails and QEMU aborts
with the following error message:

 cannot set up guest memory 's390.ram': Permission denied

Looking at the other allocator function qemu_anon_ram_alloc(), it
seems like PROT_EXEC is normally not needed for allocating the
guest RAM, and indeed, the guest also starts successfully under
z/VM when we remove the PROT_EXEC from the legacy_s390_alloc()
function. So let's get rid of that flag here to be able to run
with SELinux under z/VM, too.

Signed-off-by: Thomas Huth <address@hidden>
 target/s390x/kvm.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/target/s390x/kvm.c b/target/s390x/kvm.c
index ac47154..5167436 100644
--- a/target/s390x/kvm.c
+++ b/target/s390x/kvm.c
@@ -678,8 +678,7 @@ static void *legacy_s390_alloc(size_t size, uint64_t *align)
     void *mem;
-    mem = mmap((void *) 0x800000000ULL, size,
+    mem = mmap((void *) 0x800000000ULL, size, PROT_READ | PROT_WRITE,
                MAP_SHARED | MAP_ANONYMOUS | MAP_FIXED, -1, 0);
     return mem == MAP_FAILED ? NULL : mem;

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