[Qemu-devel] [PATCH 2/9] Allocate physical memory in low virtual address space

[Alexander Graf <agraf@suse.de>]

KVM on S390x requires the virtual address space of the guest's RAM to be
within the first 256GB.

The general direction I'd like to see KVM on S390 move is that this requirement
is losened, but for now that's what we're stuck with.

So let's just hack up qemu_ram_alloc until KVM behaves nicely :-).

Signed-off-by: Alexander Graf <agraf@suse.de>
---
 exec.c |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)

diff --git a/exec.c b/exec.c
index 076d26b..59150d0 100644
--- a/exec.c
+++ b/exec.c
@@ -2411,7 +2411,13 @@ ram_addr_t qemu_ram_alloc(ram_addr_t size)
     size = TARGET_PAGE_ALIGN(size);
     new_block = qemu_malloc(sizeof(*new_block));
 
+#if defined(TARGET_S390) && defined(CONFIG_KVM)
+    /* XXX S390 KVM requires the topmost vma of the RAM to be < 256GB */
+    new_block->host = mmap(0x1000000, size, PROT_EXEC|PROT_READ|PROT_WRITE,
+                           MAP_SHARED | MAP_ANONYMOUS, -1, 0);
+#else
     new_block->host = qemu_vmalloc(size);
+#endif
 #ifdef MADV_MERGEABLE
     madvise(new_block->host, size, MADV_MERGEABLE);
 #endif
-- 
1.6.0.2