Hi

The root cause of this problem has been found, when Guest OS do the virtio console driver probe, if virtqueue's desc addr allocated by alloc_pages_exact() in the setup_vq() function is >= 0x100000000 (it is common when the memory of VM allocated exceeds 3G), at first It will be shifted right 12 bits by Guest OS(turn into a value >= 0x100000), and then use iowrite32(iobase + VIRTIO_PCI_QUEUE_PFN) to notify Host, after unsigned int type data be shifted left 12 bits by Host, the higest bits 0x1 of virtqueue's desc addr will be lost.

I have submitted a PR for the amendment, waiting for the review and merge into the main branch. https://github.com/seL4/seL4_projects_libs/pull/43

BR. Allen

发件人: Han JingLong 韩景龙 发送时间: 2022年3月21日 20:27 收件人: 'devel@sel4.systems' devel@sel4.systems 主题: Report "Failed to touch ram region" error using virtio_console when assigned for Arm-VM more than 3G memory

Hi

I had make virtio_console work well on my environment(armv8, RAM is 8G) based on vm_multi with Linux Guest OS(512M) and Android Guest OS(<= 3G) But I meet an error(vm_ram_touch@guest_ram.c:157mailto:vm_ram_touch@guest_ram.c:157 Failed to touch ram region: Not registered RAM region) when assign for a VM(Android Guest OS) more than 3G memory.

1. Some logs are added for debugging this issue： +++ b/seL4_projects_libs/libsel4vmmplatsupport/src/drivers/virtio_emul.c @@ -86,6 +86,7 @@ static int emul_io_out(virtio_emul_t *emul, unsigned int offset, unsigned int si assert(size == 4); int queue = emul->virtq.queue; emul->virtq.queue_pfn[queue] = value; + printf("[hjl] queue_size:%d desc:%p\n", emul->virtq.queue_size[queue], (void *)(uintptr_t)(value << 12)); vring_init(&emul->virtq.vring[queue], emul->virtq.queue_size[queue], (void *)(uintptr_t)(value << 12), VIRTIO_PCI_VRING_ALIGN); break;

+++ b/seL4_projects_libs/libsel4vmmplatsupport/src/drivers/virtio_emul_helpers.c @@ -25,10 +25,43 @@ static int write_guest_mem(vm_t *vm, uintptr_t phys, void *vaddr, size_t size, s

int vm_guest_write_mem(vm_t *vm, void *data, uintptr_t address, size_t size) { + bool is_inram = false; + vm_mem_t *guest_memory = &vm->mem; + for (int i = 0; i < guest_memory->num_ram_regions; i++) { + if (guest_memory->ram_regions[i].start <= address && + guest_memory->ram_regions[i].start + guest_memory->ram_regions[i].size >= address + size) { + /* We are within a ram region*/ + is_inram = true; + } + } + + if (!is_inram) { + printf("[hjl] write mem addr:%p size:0x%lx\n", address, size); + for (int index = 0; index < guest_memory->num_ram_regions; index++) { + printf("[hjl] write mem ram_regions start:%p size:0x%lx\n", guest_memory->ram_regions[index].start, guest_memory->ram_regions[index].size); + } + } + return vm_ram_touch(vm, address, size, write_guest_mem, data); }

int vm_guest_read_mem(vm_t *vm, void *data, uintptr_t address, size_t size) { + bool is_inram = false; + vm_mem_t *guest_memory = &vm->mem; + for (int i = 0; i < guest_memory->num_ram_regions; i++) { + if (guest_memory->ram_regions[i].start <= address && + guest_memory->ram_regions[i].start + guest_memory->ram_regions[i].size >= address + size) { + /* We are within a ram region*/ + is_inram = true; + } + } + + if (!is_inram) { + printf("[hjl] read mem addr:%p size:0x%lx\n", address, size); + for (int index = 0; index < guest_memory->num_ram_regions; index++) { + printf("[hjl] read mem ram_regions start:%p size:0x%lx\n", guest_memory->ram_regions[index].start, guest_memory->ram_regions[index].size); + } + } return vm_ram_touch(vm, address, size, read_guest_mem, data); }

2. The detailed log is as follows: [hjl] queue_size:128 desc:0x8eb6000 [hjl] queue_size:128 desc:0x8eb8000 [hjl] read mem addr:0x8eb8802 size:0x2 [hjl] read mem ram_regions start:0x80000000 size:0x80000 [hjl] read mem ram_regions start:0x80080000 size:0x17cda00 [hjl] read mem ram_regions start:0x8184da00 size:0xa5b2600 [hjl] read mem ram_regions start:0x8be00000 size:0x83ae98 [hjl] read mem ram_regions start:0x8c63ae98 size:0x29c5168 [hjl] read mem ram_regions start:0x8f000000 size:0x26d35 [hjl] read mem ram_regions start:0x8f026d35 size:0xc0fd92cb vm_ram_touch@guest_ram.c:157mailto:vm_ram_touch@guest_ram.c:157 Failed to touch ram region: Not registered RAM region

3. devices.camkes configuration reference is as follows: #define VM1_RAM_BASE 0x80000000 #define VM1_RAM_SIZE 0xD0000000 #define VM1_DTB_ADDR 0x8F000000 //VM1_RAM_BASE + 0xF000000 #define VM1_INITRD_ADDR 0x8BE00000 //VM1_DTB_ADDR - VM1_INITRD_MAX_SIZE

vm1.untyped_mmios = [ "0x80000000:28", // RAM "0x90000000:28", // RAM "0xa0000000:28", // RAM "0xb0000000:28", // RAM

"0xc0000000:28", // RAM "0xd0000000:28", // RAM "0xe0000000:28", // RAM "0xf0000000:28", // RAM

"0x100000000:28", // RAM "0x110000000:28", // RAM "0x120000000:28", // RAM "0x130000000:28", // RAM

"0x140000000:28", // RAM /* "0x150000000:28", // RAM "0x160000000:28", // RAM "0x170000000:28", // RAM

"0x180000000:28", // RAM "0x190000000:28", // RAM "0x1a0000000:28", // RAM "0x1b0000000:28", // RAM */ ];

4. Present situation: At present, I tracked and found that When the Guest OS's virtio_console driver do the probe, it created the vring and iowrite to notify VMM of the virtqueue desc 's physical address in setup_vq()

/* create the vring */ static void *vring_alloc_queue(struct virtio_device *vdev, size_t size, dma_addr_t *dma_handle, gfp_t flag) { ...... void *queue = alloc_pages_exact(PAGE_ALIGN(size), flag); if (queue) { phys_addr_t phys_addr = virt_to_phys(queue); *dma_handle = (dma_addr_t)phys_addr;

/* activate the queue */ iowrite32(virtqueue_get_desc_addr(vq) >> VIRTIO_PCI_QUEUE_ADDR_SHIFT, vp_dev->ioaddr + VIRTIO_PCI_QUEUE_PFN);

I'm very confused why is the physical memory allocated for virtqueue desc not within the effective memory range of VM when assign the memory to it exceeds 3G?

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