Re: [kvm-unit-tests PATCH v3 2/3] s390x: define UV compatible I/O allocation

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On 1/20/21 12:01 PM, Thomas Huth wrote:
On 19/01/2021 20.52, Pierre Morel wrote:
To centralize the memory allocation for I/O we define
the alloc_io_page/free_io_page functions which share the I/O
memory with the host in case the guest runs with
protected virtualization.

Signed-off-by: Pierre Morel <pmorel@xxxxxxxxxxxxx>
---
  lib/s390x/malloc_io.c | 50 +++++++++++++++++++++++++++++++++++++++++++
  lib/s390x/malloc_io.h | 18 ++++++++++++++++
  s390x/Makefile        |  1 +
  3 files changed, 69 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 0000000..2a946e0
--- /dev/null
+++ b/lib/s390x/malloc_io.c
@@ -0,0 +1,50 @@
+/*
+ * I/O page allocation
+ *
+ * Copyright (c) 2021 IBM Corp
+ *
+ * Authors:
+ *  Pierre Morel <pmorel@xxxxxxxxxxxxx>
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2.

Janosch recently started to introduce SPDX identifieres to the s390x code, so I think it would be good to use them here, too.

+ * Using this interface provide host access to the allocated pages in
+ * case the guest is a secure 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>
+
+void *alloc_io_page(int size)
+{
+    void *p;
+
+    assert(size <= PAGE_SIZE);

Apart from the assert() statement, the size parameter seems to be completely unused. It's also weird to have the function named

right.

alloc_something_page() and then have a parameter that takes bytes. Thus I'd suggest to either drop the size parameter completely, or to rename the function to alloc_io_mem and then to alloc multiple pages below in case the size is bigger than PAGE_SIZE. Or maybe even to name the function alloc_io_pages and then use "int num_pages" as a parameter, allowing to allocate multiple pages at once?

OK, may bet using order as with the alloc_pages_flags would be fine.
Then I will need a new flag in the pages.


+
+    p = alloc_pages_flags(1, AREA_DMA31);

humm 0 here (Claudio)

+    if (!p)
+        return NULL;
+    memset(p, 0, PAGE_SIZE);
+
+    if (!test_facility(158))
+        return p;
+
+    if (uv_set_shared((unsigned long)p) == 0)
+        return p;
+
+    free_pages(p);
+    return NULL;
+}
+
+void free_io_page(void *p)
+{
+    if (test_facility(158))
+        uv_remove_shared((unsigned long)p);
+    free_pages(p);
+}
diff --git a/lib/s390x/malloc_io.h b/lib/s390x/malloc_io.h
new file mode 100644
index 0000000..f780191
--- /dev/null
+++ b/lib/s390x/malloc_io.h
@@ -0,0 +1,18 @@
+/*
+ * I/O allocations
+ *
+ * Copyright (c) 2021 IBM Corp
+ *
+ * Authors:
+ *  Pierre Morel <pmorel@xxxxxxxxxxxxx>
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2.
+ */
Please also add SPDX license information here.

Will do.

Thanks for reviewing,
Pierre


  Thomas


--
Pierre Morel
IBM Lab Boeblingen



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