diff options
| -rw-r--r-- | migration/postcopy-ram.c | 94 |
1 files changed, 88 insertions, 6 deletions
diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c index cf62fc756f..0de68e8b25 100644 --- a/migration/postcopy-ram.c +++ b/migration/postcopy-ram.c @@ -61,16 +61,67 @@ struct PostcopyDiscardState { #include <sys/eventfd.h> #include <linux/userfaultfd.h> -static bool ufd_version_check(int ufd, MigrationIncomingState *mis) + +/** + * receive_ufd_features: check userfault fd features, to request only supported + * features in the future. + * + * Returns: true on success + * + * __NR_userfaultfd - should be checked before + * @features: out parameter will contain uffdio_api.features provided by kernel + * in case of success + */ +static bool receive_ufd_features(uint64_t *features) { - struct uffdio_api api_struct; - uint64_t ioctl_mask; + struct uffdio_api api_struct = {0}; + int ufd; + bool ret = true; + + /* if we are here __NR_userfaultfd should exists */ + ufd = syscall(__NR_userfaultfd, O_CLOEXEC); + if (ufd == -1) { + error_report("%s: syscall __NR_userfaultfd failed: %s", __func__, + strerror(errno)); + return false; + } + /* ask features */ api_struct.api = UFFD_API; api_struct.features = 0; if (ioctl(ufd, UFFDIO_API, &api_struct)) { error_report("%s: UFFDIO_API failed: %s", __func__, strerror(errno)); + ret = false; + goto release_ufd; + } + + *features = api_struct.features; + +release_ufd: + close(ufd); + return ret; +} + +/** + * request_ufd_features: this function should be called only once on a newly + * opened ufd, subsequent calls will lead to error. + * + * Returns: true on succes + * + * @ufd: fd obtained from userfaultfd syscall + * @features: bit mask see UFFD_API_FEATURES + */ +static bool request_ufd_features(int ufd, uint64_t features) +{ + struct uffdio_api api_struct = {0}; + uint64_t ioctl_mask; + + api_struct.api = UFFD_API; + api_struct.features = features; + if (ioctl(ufd, UFFDIO_API, &api_struct)) { + error_report("%s failed: UFFDIO_API failed: %s", __func__, + strerror(errno)); return false; } @@ -82,11 +133,42 @@ static bool ufd_version_check(int ufd, MigrationIncomingState *mis) return false; } + return true; +} + +static bool ufd_check_and_apply(int ufd, MigrationIncomingState *mis) +{ + uint64_t asked_features = 0; + static uint64_t supported_features; + + /* + * it's not possible to + * request UFFD_API twice per one fd + * userfault fd features is persistent + */ + if (!supported_features) { + if (!receive_ufd_features(&supported_features)) { + error_report("%s failed", __func__); + return false; + } + } + + /* + * request features, even if asked_features is 0, due to + * kernel expects UFFD_API before UFFDIO_REGISTER, per + * userfault file descriptor + */ + if (!request_ufd_features(ufd, asked_features)) { + error_report("%s failed: features %" PRIu64, __func__, + asked_features); + return false; + } + if (getpagesize() != ram_pagesize_summary()) { bool have_hp = false; /* We've got a huge page */ #ifdef UFFD_FEATURE_MISSING_HUGETLBFS - have_hp = api_struct.features & UFFD_FEATURE_MISSING_HUGETLBFS; + have_hp = supported_features & UFFD_FEATURE_MISSING_HUGETLBFS; #endif if (!have_hp) { error_report("Userfault on this host does not support huge pages"); @@ -147,7 +229,7 @@ bool postcopy_ram_supported_by_host(MigrationIncomingState *mis) } /* Version and features check */ - if (!ufd_version_check(ufd, mis)) { + if (!ufd_check_and_apply(ufd, mis)) { goto out; } @@ -523,7 +605,7 @@ int postcopy_ram_enable_notify(MigrationIncomingState *mis) * Although the host check already tested the API, we need to * do the check again as an ABI handshake on the new fd. */ - if (!ufd_version_check(mis->userfault_fd, mis)) { + if (!ufd_check_and_apply(mis->userfault_fd, mis)) { return -1; } |