diff mbox series

[PULL,38/47] memfd: add hugetlbsize argument

Message ID 1517858941-5538-39-git-send-email-pbonzini@redhat.com
State New
Headers show
Series [PULL,01/47] memory: update comments and fix some typos | expand

Commit Message

Paolo Bonzini Feb. 5, 2018, 7:28 p.m. UTC 
From: Marc-André Lureau <marcandre.lureau@redhat.com>

Learn to specificy hugetlb size as qemu_memfd_create() argument.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20180201132757.23063-4-marcandre.lureau@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 include/qemu/memfd.h |  2 +-
 util/memfd.c         | 22 ++++++++++++++++++----
 2 files changed, 19 insertions(+), 5 deletions(-)

Comments

Peter Maydell April 27, 2018, 12:42 p.m. UTC | #1 
On 5 February 2018 at 19:28, Paolo Bonzini <pbonzini@redhat.com> wrote:
> From: Marc-André Lureau <marcandre.lureau@redhat.com>
>
> Learn to specificy hugetlb size as qemu_memfd_create() argument.

>  int qemu_memfd_create(const char *name, size_t size, bool hugetlb,
> -                      unsigned int seals, Error **errp)
> +                      uint64_t hugetlbsize, unsigned int seals, Error **errp)
>  {
> +    int htsize = hugetlbsize ? ctz64(hugetlbsize) : 0;
> +
> +    if (htsize && 1 << htsize != hugetlbsize) {
> +        error_setg(errp, "Hugepage size must be a power of 2");
> +        return -1;
> +    }
> +
> +    htsize = htsize << MFD_HUGE_SHIFT;

Hi; Coverity complains about this function (CID 1385858) because
we calculate a bit poisition htsize which could be up to 63, but
then use it in "1 << htsize" which is a 32-bit integer calculation
and could push the 1 off the top of the value.

This should be "1ULL", though of course a hugetlbsize of 4GB
is not very plausible.

PS: the variable name is "hugetlbsize" but the error message
says "hugepage size" -- is it a TLB size or a page size ?

thanks
-- PMM
diff mbox series

Patch

diff --git a/include/qemu/memfd.h b/include/qemu/memfd.h
index 1d3ecc7..de10198 100644
--- a/include/qemu/memfd.h
+++ b/include/qemu/memfd.h
@@ -17,7 +17,7 @@ 
 #endif
 
 int qemu_memfd_create(const char *name, size_t size, bool hugetlb,
-                      unsigned int seals, Error **errp);
+                      uint64_t hugetlbsize, unsigned int seals, Error **errp);
 void *qemu_memfd_alloc(const char *name, size_t size, unsigned int seals,
                        int *fd, Error **errp);
 void qemu_memfd_free(void *ptr, size_t size, int fd);
diff --git a/util/memfd.c b/util/memfd.c
index 7594af7..07d579e 100644
--- a/util/memfd.c
+++ b/util/memfd.c
@@ -29,6 +29,7 @@ 
 
 #include "qapi/error.h"
 #include "qemu/memfd.h"
+#include "qemu/host-utils.h"
 
 #if defined CONFIG_LINUX && !defined CONFIG_MEMFD
 #include <sys/syscall.h>
@@ -56,9 +57,22 @@  static int memfd_create(const char *name, unsigned int flags)
 #define MFD_HUGETLB 0x0004U
 #endif
 
+#ifndef MFD_HUGE_SHIFT
+#define MFD_HUGE_SHIFT 26
+#endif
+
 int qemu_memfd_create(const char *name, size_t size, bool hugetlb,
-                      unsigned int seals, Error **errp)
+                      uint64_t hugetlbsize, unsigned int seals, Error **errp)
 {
+    int htsize = hugetlbsize ? ctz64(hugetlbsize) : 0;
+
+    if (htsize && 1 << htsize != hugetlbsize) {
+        error_setg(errp, "Hugepage size must be a power of 2");
+        return -1;
+    }
+
+    htsize = htsize << MFD_HUGE_SHIFT;
+
 #ifdef CONFIG_LINUX
     int mfd = -1;
     unsigned int flags = MFD_CLOEXEC;
@@ -68,8 +82,8 @@  int qemu_memfd_create(const char *name, size_t size, bool hugetlb,
     }
     if (hugetlb) {
         flags |= MFD_HUGETLB;
+        flags |= htsize;
     }
-
     mfd = memfd_create(name, flags);
     if (mfd < 0) {
         goto err;
@@ -104,11 +118,11 @@  void *qemu_memfd_alloc(const char *name, size_t size, unsigned int seals,
                        int *fd, Error **errp)
 {
     void *ptr;
-    int mfd = qemu_memfd_create(name, size, false, seals, NULL);
+    int mfd = qemu_memfd_create(name, size, false, 0, seals, NULL);
 
     /* some systems have memfd without sealing */
     if (mfd == -1) {
-        mfd = qemu_memfd_create(name, size, false, 0, NULL);
+        mfd = qemu_memfd_create(name, size, false, 0, 0, NULL);
     }
 
     if (mfd == -1) {