Allocate all guest ram backed by memfd/ftruncate instead of anonymous mmap. This will make it easier to use kvm with fd-based kvm guest memory proposals [*]. It also would make it easier to use ipc memory sharing should that be needed in the future. Signed-off-by: Fuad Tabba <tabba@xxxxxxxxxx> [*] https://lore.kernel.org/all/20221025151344.3784230-1-chao.p.peng@xxxxxxxxxxxxxxx/ --- include/kvm/kvm.h | 1 + include/kvm/util.h | 3 +++ kvm.c | 4 ++++ util/util.c | 33 ++++++++++++++++++++------------- 4 files changed, 28 insertions(+), 13 deletions(-) diff --git a/include/kvm/kvm.h b/include/kvm/kvm.h index 3872dc6..d0d519b 100644 --- a/include/kvm/kvm.h +++ b/include/kvm/kvm.h @@ -87,6 +87,7 @@ struct kvm { struct kvm_config cfg; int sys_fd; /* For system ioctls(), i.e. /dev/kvm */ int vm_fd; /* For VM ioctls() */ + int ram_fd; /* For guest memory. */ timer_t timerid; /* Posix timer for interrupts */ int nrcpus; /* Number of cpus to run */ diff --git a/include/kvm/util.h b/include/kvm/util.h index 61a205b..369603b 100644 --- a/include/kvm/util.h +++ b/include/kvm/util.h @@ -140,6 +140,9 @@ static inline int pow2_size(unsigned long x) } struct kvm; +int memfd_alloc(u64 size, bool hugetlb, u64 blk_size); +void *mmap_anon_or_hugetlbfs_align(struct kvm *kvm, const char *htlbfs_path, + u64 size, u64 align); void *mmap_anon_or_hugetlbfs(struct kvm *kvm, const char *htlbfs_path, u64 size); #endif /* KVM__UTIL_H */ diff --git a/kvm.c b/kvm.c index 78bc0d8..ed29d68 100644 --- a/kvm.c +++ b/kvm.c @@ -160,6 +160,7 @@ struct kvm *kvm__new(void) mutex_init(&kvm->mem_banks_lock); kvm->sys_fd = -1; kvm->vm_fd = -1; + kvm->ram_fd = -1; #ifdef KVM_BRLOCK_DEBUG kvm->brlock_sem = (pthread_rwlock_t) PTHREAD_RWLOCK_INITIALIZER; @@ -174,6 +175,9 @@ int kvm__exit(struct kvm *kvm) kvm__arch_delete_ram(kvm); + if (kvm->ram_fd >= 0) + close(kvm->ram_fd); + list_for_each_entry_safe(bank, tmp, &kvm->mem_banks, list) { list_del(&bank->list); free(bank); diff --git a/util/util.c b/util/util.c index d3483d8..278bcc2 100644 --- a/util/util.c +++ b/util/util.c @@ -102,36 +102,38 @@ static u64 get_hugepage_blk_size(const char *htlbfs_path) return sfs.f_bsize; } -static void *mmap_hugetlbfs(struct kvm *kvm, const char *htlbfs_path, u64 size, u64 blk_size) +int memfd_alloc(u64 size, bool hugetlb, u64 blk_size) { const char *name = "kvmtool"; unsigned int flags = 0; int fd; - void *addr; - int htsize = __builtin_ctzl(blk_size); - if ((1ULL << htsize) != blk_size) - die("Hugepage size must be a power of 2.\n"); + if (hugetlb) { + int htsize = __builtin_ctzl(blk_size); - flags |= MFD_HUGETLB; - flags |= htsize << MFD_HUGE_SHIFT; + if ((1ULL << htsize) != blk_size) + die("Hugepage size must be a power of 2.\n"); + + flags |= MFD_HUGETLB; + flags |= htsize << MFD_HUGE_SHIFT; + } fd = memfd_create(name, flags); if (fd < 0) - die("Can't memfd_create for hugetlbfs map\n"); + die("Can't memfd_create for memory map\n"); + if (ftruncate(fd, size) < 0) die("Can't ftruncate for mem mapping size %lld\n", (unsigned long long)size); - addr = mmap(NULL, size, PROT_RW, MAP_PRIVATE, fd, 0); - close(fd); - return addr; + return fd; } /* This function wraps the decision between hugetlbfs map (if requested) or normal mmap */ void *mmap_anon_or_hugetlbfs(struct kvm *kvm, const char *htlbfs_path, u64 size) { u64 blk_size = 0; + int fd; /* * We don't /need/ to map guest RAM from hugetlbfs, but we do so @@ -146,9 +148,14 @@ void *mmap_anon_or_hugetlbfs(struct kvm *kvm, const char *htlbfs_path, u64 size) } kvm->ram_pagesize = blk_size; - return mmap_hugetlbfs(kvm, htlbfs_path, size, blk_size); } else { kvm->ram_pagesize = getpagesize(); - return mmap(NULL, size, PROT_RW, MAP_ANON_NORESERVE, -1, 0); } + + fd = memfd_alloc(size, htlbfs_path, blk_size); + if (fd < 0) + return MAP_FAILED; + + kvm->ram_fd = fd; + return mmap(NULL, size, PROT_RW, MAP_PRIVATE, kvm->ram_fd, 0); } -- 2.38.1.431.g37b22c650d-goog
