| Message ID | 20221115111549.2784927-7-tabba@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Use memfd for guest vm memory allocation | expand |
Hi, On Tue, Nov 15, 2022 at 11:15:38AM +0000, Fuad Tabba wrote: > This removes the need of using a temporary file for the fd. I'm confused by this. The man page for memfd_create says that it creates an anonymous file that lives in RAM. > > Signed-off-by: Fuad Tabba <tabba@google.com> > --- > util/util.c | 25 ++++++++++++++++++++----- > 1 file changed, 20 insertions(+), 5 deletions(-) > > diff --git a/util/util.c b/util/util.c > index e6c0951..d6ceb5d 100644 > --- a/util/util.c > +++ b/util/util.c > @@ -10,6 +10,14 @@ > #include <sys/stat.h> > #include <sys/statfs.h> > > +#ifndef MFD_HUGETLB > +#define MFD_HUGETLB 0x0004U > +#endif > + > +#ifndef MFD_HUGE_SHIFT > +#define MFD_HUGE_SHIFT 26 > +#endif Hm... on my machine these are defined in linux/memfd.h, maybe you are missing the include? > + > static void report(const char *prefix, const char *err, va_list params) > { > char msg[1024]; > @@ -96,10 +104,12 @@ static u64 get_hugepage_blk_size(const char *htlbfs_path) > > static void *mmap_hugetlbfs(struct kvm *kvm, const char *htlbfs_path, u64 size) > { > - char mpath[PATH_MAX]; > + const char *name = "kvmtool"; > + unsigned int flags = 0; > int fd; > void *addr; > u64 blk_size; > + int htsize; > > blk_size = get_hugepage_blk_size(htlbfs_path); > if (blk_size == 0 || blk_size > size) { > @@ -107,13 +117,18 @@ static void *mmap_hugetlbfs(struct kvm *kvm, const char *htlbfs_path, u64 size) > (unsigned long long)blk_size, (unsigned long long)size); > } > > + htsize = __builtin_ctzl(blk_size); > + if ((1ULL << htsize) != blk_size) > + die("Hugepage size must be a power of 2.\n"); > + > + flags |= MFD_HUGETLB; > + flags |= htsize << MFD_HUGE_SHIFT; If I understand the intention correctly, this entire sequence can be rewritten using is_power_of_two() from util.h: if (!is_power_of_two(blk_size)) die("Hugepage size must be a power of 2"); flags |= MFD_HUGETLB; flags |= blk_size << MFD_HUGE_SHIFT; Also, die() automatically adds the newline at the end of the string. That's unless you specifically wanted two newline characters at the end of the message. > + > kvm->ram_pagesize = blk_size; > > - snprintf(mpath, PATH_MAX, "%s/kvmtoolXXXXXX", htlbfs_path); > - fd = mkstemp(mpath); > + fd = memfd_create(name, flags); > if (fd < 0) > - die("Can't open %s for hugetlbfs map\n", mpath); > - unlink(mpath); > + die("Can't memfd_create for hugetlbfs map\n"); die_perror("memfd_create")? That way you also print the error number and the message associated with it. Same thing with the other die statements here, replacing them with die_perror() looks like it would be helpful. Thanks, Alex > if (ftruncate(fd, size) < 0) > die("Can't ftruncate for mem mapping size %lld\n", > (unsigned long long)size); > -- > 2.38.1.431.g37b22c650d-goog >
Hi, On Thu, Nov 24, 2022 at 10:19 AM Alexandru Elisei <alexandru.elisei@arm.com> wrote: > > Hi, > > On Tue, Nov 15, 2022 at 11:15:38AM +0000, Fuad Tabba wrote: > > This removes the need of using a temporary file for the fd. > > I'm confused by this. The man page for memfd_create says that it creates an > anonymous file that lives in RAM. I'm referring for the need to create a temporary file in the hugetlbfs path. > > > > > Signed-off-by: Fuad Tabba <tabba@google.com> > > --- > > util/util.c | 25 ++++++++++++++++++++----- > > 1 file changed, 20 insertions(+), 5 deletions(-) > > > > diff --git a/util/util.c b/util/util.c > > index e6c0951..d6ceb5d 100644 > > --- a/util/util.c > > +++ b/util/util.c > > @@ -10,6 +10,14 @@ > > #include <sys/stat.h> > > #include <sys/statfs.h> > > > > +#ifndef MFD_HUGETLB > > +#define MFD_HUGETLB 0x0004U > > +#endif > > + > > +#ifndef MFD_HUGE_SHIFT > > +#define MFD_HUGE_SHIFT 26 > > +#endif > > Hm... on my machine these are defined in linux/memfd.h, maybe you are > missing the include? Ack. I'll replace them with the include. > > > + > > static void report(const char *prefix, const char *err, va_list params) > > { > > char msg[1024]; > > @@ -96,10 +104,12 @@ static u64 get_hugepage_blk_size(const char *htlbfs_path) > > > > static void *mmap_hugetlbfs(struct kvm *kvm, const char *htlbfs_path, u64 size) > > { > > - char mpath[PATH_MAX]; > > + const char *name = "kvmtool"; > > + unsigned int flags = 0; > > int fd; > > void *addr; > > u64 blk_size; > > + int htsize; > > > > blk_size = get_hugepage_blk_size(htlbfs_path); > > if (blk_size == 0 || blk_size > size) { > > @@ -107,13 +117,18 @@ static void *mmap_hugetlbfs(struct kvm *kvm, const char *htlbfs_path, u64 size) > > (unsigned long long)blk_size, (unsigned long long)size); > > } > > > > + htsize = __builtin_ctzl(blk_size); > > + if ((1ULL << htsize) != blk_size) > > + die("Hugepage size must be a power of 2.\n"); > > + > > + flags |= MFD_HUGETLB; > > + flags |= htsize << MFD_HUGE_SHIFT; > > If I understand the intention correctly, this entire sequence can be > rewritten using is_power_of_two() from util.h: > > if (!is_power_of_two(blk_size)) > die("Hugepage size must be a power of 2"); This is simpler, yes. > > Also, die() automatically adds the newline at the end of the string. > That's unless you specifically wanted two newline characters at the end of > the message. Ack. > > > + > > kvm->ram_pagesize = blk_size; > > > > - snprintf(mpath, PATH_MAX, "%s/kvmtoolXXXXXX", htlbfs_path); > > - fd = mkstemp(mpath); > > + fd = memfd_create(name, flags); > > if (fd < 0) > > - die("Can't open %s for hugetlbfs map\n", mpath); > > - unlink(mpath); > > + die("Can't memfd_create for hugetlbfs map\n"); > > die_perror("memfd_create")? That way you also print the error number and > the message associated with it. Same thing with the other die statements > here, replacing them with die_perror() looks like it would be helpful. Will do. Cheers, /fuad > > Thanks, > Alex > > > if (ftruncate(fd, size) < 0) > > die("Can't ftruncate for mem mapping size %lld\n", > > (unsigned long long)size); > > -- > > 2.38.1.431.g37b22c650d-goog > >
diff --git a/util/util.c b/util/util.c index e6c0951..d6ceb5d 100644 --- a/util/util.c +++ b/util/util.c @@ -10,6 +10,14 @@ #include <sys/stat.h> #include <sys/statfs.h> +#ifndef MFD_HUGETLB +#define MFD_HUGETLB 0x0004U +#endif + +#ifndef MFD_HUGE_SHIFT +#define MFD_HUGE_SHIFT 26 +#endif + static void report(const char *prefix, const char *err, va_list params) { char msg[1024]; @@ -96,10 +104,12 @@ static u64 get_hugepage_blk_size(const char *htlbfs_path) static void *mmap_hugetlbfs(struct kvm *kvm, const char *htlbfs_path, u64 size) { - char mpath[PATH_MAX]; + const char *name = "kvmtool"; + unsigned int flags = 0; int fd; void *addr; u64 blk_size; + int htsize; blk_size = get_hugepage_blk_size(htlbfs_path); if (blk_size == 0 || blk_size > size) { @@ -107,13 +117,18 @@ static void *mmap_hugetlbfs(struct kvm *kvm, const char *htlbfs_path, u64 size) (unsigned long long)blk_size, (unsigned long long)size); } + htsize = __builtin_ctzl(blk_size); + if ((1ULL << htsize) != blk_size) + die("Hugepage size must be a power of 2.\n"); + + flags |= MFD_HUGETLB; + flags |= htsize << MFD_HUGE_SHIFT; + kvm->ram_pagesize = blk_size; - snprintf(mpath, PATH_MAX, "%s/kvmtoolXXXXXX", htlbfs_path); - fd = mkstemp(mpath); + fd = memfd_create(name, flags); if (fd < 0) - die("Can't open %s for hugetlbfs map\n", mpath); - unlink(mpath); + die("Can't memfd_create for hugetlbfs map\n"); if (ftruncate(fd, size) < 0) die("Can't ftruncate for mem mapping size %lld\n", (unsigned long long)size);
This removes the need of using a temporary file for the fd. Signed-off-by: Fuad Tabba <tabba@google.com> --- util/util.c | 25 ++++++++++++++++++++----- 1 file changed, 20 insertions(+), 5 deletions(-)