[kvm-unit-tests GIT PULL 03/16] s390x: define UV compatible I/O allocation

Janosch Frank
2021-03-08T14:34:25Z

From: Pierre Morel <pmorel@linux.ibm.com>

To centralize the memory allocation for I/O we define
the alloc_io_mem/free_io_mem functions which share the I/O
memory with the host in case the guest runs with
protected virtualization.

These functions allocate on a page integral granularity to
ensure a dedicated sharing of the allocated objects.

Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Acked-by: Janosch Frank <frankja@de.ibm.com>
Acked-by: Thomas Huth <thuth@redhat.com>
Message-Id: <1611322060-1972-3-git-send-email-pmorel@linux.ibm.com>
Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
---
lib/s390x/malloc_io.c | 71 +++++++++++++++++++++++++++++++++++++++++++
lib/s390x/malloc_io.h | 45 +++++++++++++++++++++++++++
s390x/Makefile | 1 +
3 files changed, 117 insertions(+)
create mode 100644 lib/s390x/malloc_io.c
create mode 100644 lib/s390x/malloc_io.h

diff --git a/lib/s390x/malloc_io.c b/lib/s390x/malloc_io.c
new file mode 100644
index 00000000..1dcf1691
--- /dev/null
+++ b/lib/s390x/malloc_io.c
@@ -0,0 +1,71 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * I/O page allocation
+ *
+ * Copyright (c) 2021 IBM Corp
+ *
+ * Authors:
+ * Pierre Morel <pmorel@linux.ibm.com>
+ *
+ * Using this interface provide host access to the allocated pages in
+ * case the guest is a protected guest.
+ * This is needed for I/O buffers.
+ *
+ */
+#include <libcflat.h>
+#include <asm/page.h>
+#include <asm/uv.h>
+#include <malloc_io.h>
+#include <alloc_page.h>
+#include <asm/facility.h>
+#include <bitops.h>
+
+static int share_pages(void *p, int count)
+{
+ int i = 0;
+
+ for (i = 0; i < count; i++, p += PAGE_SIZE)
+ if (uv_set_shared((unsigned long)p))
+ break;
+ return i;
+}
+
+static void unshare_pages(void *p, int count)
+{
+ int i;
+
+ for (i = count; i > 0; i--, p += PAGE_SIZE)
+ uv_remove_shared((unsigned long)p);
+}
+
+void *alloc_io_mem(int size, int flags)
+{
+ int order = get_order(size >> PAGE_SHIFT);
+ void *p;
+ int n;
+
+ assert(size);
+
+ p = alloc_pages_flags(order, AREA_DMA31 | flags);
+ if (!p || !test_facility(158))
+ return p;
+
+ n = share_pages(p, 1 << order);
+ if (n == 1 << order)
+ return p;
+
+ unshare_pages(p, n);
+ free_pages(p);
+ return NULL;
+}
+
+void free_io_mem(void *p, int size)
+{
+ int order = get_order(size >> PAGE_SHIFT);
+
+ assert(IS_ALIGNED((uintptr_t)p, PAGE_SIZE));
+
+ if (test_facility(158))
+ unshare_pages(p, 1 << order);
+ free_pages(p);
+}
diff --git a/lib/s390x/malloc_io.h b/lib/s390x/malloc_io.h
new file mode 100644
index 00000000..cc5fad79
--- /dev/null
+++ b/lib/s390x/malloc_io.h
@@ -0,0 +1,45 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * I/O allocations
+ *
+ * Copyright (c) 2021 IBM Corp
+ *
+ * Authors:
+ * Pierre Morel <pmorel@linux.ibm.com>
+ *
+ */
+#ifndef _S390X_MALLOC_IO_H_
+#define _S390X_MALLOC_IO_H_
+
+/*
+ * Allocates a page aligned page bound range of contiguous real or
+ * absolute memory in the DMA31 region large enough to contain size
+ * bytes.
+ * If Protected Virtualisation facility is present, shares the pages
+ * with the host.
+ * If all the pages for the specified size cannot be reserved,
+ * the function rewinds the partial allocation and a NULL pointer
+ * is returned.
+ *
+ * @size: the minimal size allocated in byte.
+ * @flags: the flags used for the underlying page allocator.
+ *
+ * Errors:
+ * The allocation will assert the size parameter, will fail if the
+ * underlying page allocator fail or in the case of protected
+ * virtualisation if the sharing of the pages fails.
+ *
+ * Returns a pointer to the first page in case of success, NULL otherwise.
+ */
+void *alloc_io_mem(int size, int flags);
+
+/*
+ * Frees a previously memory space allocated by alloc_io_mem.
+ * If Protected Virtualisation facility is present, unshares the pages
+ * with the host.
+ * The address must be aligned on a page boundary otherwise an assertion
+ * breaks the program.
+ */
+void free_io_mem(void *p, int size);
+
+#endif /* _S390X_MALLOC_IO_H_ */
diff --git a/s390x/Makefile b/s390x/Makefile
index 08d85c9f..f3b0fccf 100644
--- a/s390x/Makefile
+++ b/s390x/Makefile
@@ -64,6 +64,7 @@ cflatobjs += lib/s390x/smp.o
cflatobjs += lib/s390x/vm.o
cflatobjs += lib/s390x/css_dump.o
cflatobjs += lib/s390x/css_lib.o
+cflatobjs += lib/s390x/malloc_io.o

OBJDIRS += lib/s390x

--
2.29.2