The default block size is same as to the THP size, which is either retrieved from "/sys/kernel/mm/transparent_hugepage/hpage_pmd_size" or hardcoded to 2MB. There are flaws in both mechanisms and this intends to fix them up.
* When "/sys/kernel/mm/transparent_hugepage/hpage_pmd_size" is used to getting the THP size, 32MB and 512MB are valid values when we have 16KB and 64KB page size on ARM64. * When the hardcoded THP size is used, 2MB, 32MB and 512MB are valid values when we have 4KB, 16KB and 64KB page sizes on ARM64. Co-developed-by: David Hildenbrand <da...@redhat.com> Signed-off-by: Gavin Shan <gs...@redhat.com> --- hw/virtio/virtio-mem.c | 32 ++++++++++++++++++++------------ 1 file changed, 20 insertions(+), 12 deletions(-) diff --git a/hw/virtio/virtio-mem.c b/hw/virtio/virtio-mem.c index ac7a40f514..8f3c95300f 100644 --- a/hw/virtio/virtio-mem.c +++ b/hw/virtio/virtio-mem.c @@ -38,14 +38,25 @@ */ #define VIRTIO_MEM_MIN_BLOCK_SIZE ((uint32_t)(1 * MiB)) -#if defined(__x86_64__) || defined(__arm__) || defined(__aarch64__) || \ - defined(__powerpc64__) -#define VIRTIO_MEM_DEFAULT_THP_SIZE ((uint32_t)(2 * MiB)) -#else - /* fallback to 1 MiB (e.g., the THP size on s390x) */ -#define VIRTIO_MEM_DEFAULT_THP_SIZE VIRTIO_MEM_MIN_BLOCK_SIZE +static uint32_t virtio_mem_default_thp_size(void) +{ + uint32_t default_thp_size = VIRTIO_MEM_MIN_BLOCK_SIZE; + +#if defined(__x86_64__) || defined(__arm__) || defined(__powerpc64__) + default_thp_size = (uint32_t)(2 * MiB); +#elif defined(__aarch64__) + if (qemu_real_host_page_size == (4 * KiB)) { + default_thp_size = (uint32_t)(2 * MiB); + } else if (qemu_real_host_page_size == (16 * KiB)) { + default_thp_size = (uint32_t)(32 * MiB); + } else if (qemu_real_host_page_size == (64 * KiB)) { + default_thp_size = (uint32_t)(512 * MiB); + } #endif + return default_thp_size; +} + /* * We want to have a reasonable default block size such that * 1. We avoid splitting THPs when unplugging memory, which degrades @@ -78,11 +89,8 @@ static uint32_t virtio_mem_thp_size(void) if (g_file_get_contents(HPAGE_PMD_SIZE_PATH, &content, NULL, NULL) && !qemu_strtou64(content, &endptr, 0, &tmp) && (!endptr || *endptr == '\n')) { - /* - * Sanity-check the value, if it's too big (e.g., aarch64 with 64k base - * pages) or weird, fallback to something smaller. - */ - if (!tmp || !is_power_of_2(tmp) || tmp > 16 * MiB) { + /* Sanity-check the value and fallback to something reasonable. */ + if (!tmp || !is_power_of_2(tmp)) { warn_report("Read unsupported THP size: %" PRIx64, tmp); } else { thp_size = tmp; @@ -90,7 +98,7 @@ static uint32_t virtio_mem_thp_size(void) } if (!thp_size) { - thp_size = VIRTIO_MEM_DEFAULT_THP_SIZE; + thp_size = virtio_mem_default_thp_size(); warn_report("Could not detect THP size, falling back to %" PRIx64 " MiB.", thp_size / MiB); } -- 2.23.0