check vfio dma allocation size before allocating

src/libixy-vfio.c

@@ -22,8 +22,6 @@
 #define MAX_INTERRUPT_VECTORS 32
 #define MSIX_IRQ_SET_BUF_LEN (sizeof(struct vfio_irq_set) + sizeof(int) * (MAX_INTERRUPT_VECTORS + 1))
 
-ssize_t MIN_DMA_MEMORY = 4096; // we can not allocate less than page_size memory
-
 void vfio_enable_dma(int device_fd) {
 	// write to the command register (offset 4) in the PCIe config space
 	int command_register_offset = 4;
@@ -301,7 +299,7 @@ uint64_t vfio_map_dma(void* vaddr, uint32_t size) {
 	struct vfio_iommu_type1_dma_map dma_map = {
 		.vaddr = (uint64_t) vaddr,
 		.iova = iova,
-		.size = size < MIN_DMA_MEMORY ? MIN_DMA_MEMORY : size,
+		.size = size,
 		.argsz = sizeof(dma_map),
 		.flags = VFIO_DMA_MAP_FLAG_READ | VFIO_DMA_MAP_FLAG_WRITE};
 	int cfd = get_vfio_container();

src/memory.c

@@ -19,6 +19,8 @@
 // this variable is unused.
 volatile int VFIO_CONTAINER_FILE_DESCRIPTOR = -1;
 
+size_t MIN_DMA_MEMORY = 4096; // we can not allocate less than page_size memory
+
 // translate a virtual address to a physical one via /proc/self/pagemap
 static uintptr_t virt_to_phys(void* virt) {
 	long pagesize = sysconf(_SC_PAGESIZE);
@@ -45,6 +47,9 @@ struct dma_memory memory_allocate_dma(size_t size, bool require_contiguous) {
 	if (VFIO_CONTAINER_FILE_DESCRIPTOR != -1) {
 		// VFIO == -1 means that there is no VFIO container set, i.e. VFIO / IOMMU is not activated
 		debug("allocating dma memory via VFIO");
+		if (size < MIN_DMA_MEMORY) {
+			size = MIN_DMA_MEMORY;
+		}
 		void* virt_addr = (void*) check_err(mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANONYMOUS | MAP_HUGETLB | MAP_HUGE_2MB, -1, 0), "mmap hugepage");
 		// create IOMMU mapping
 		uint64_t iova = (uint64_t) vfio_map_dma(virt_addr, size);