On Thu, Jun 26, 2014 at 11:01:32PM +0200, Damjan Marion wrote:
> Old code was affected by memory gaps which resulted in buffer pointers
> pointing to address outside of the mapped regions.
>
> Here we are introducing following changes:
> - new function qemu_get_ram_block_host_ptr() returns host pointer
> to the ram block, it is needed to calculate offset of specific
> region in the host memory
> - new field mmap_offset is added to the VhostUserMemoryRegion. It
> contains offset where specific region starts in the mapped memory.
> As there is stil no wider adoption of vhost-user agreement was made
> that we will not bump version number due to this change
> - other fileds in VhostUserMemoryRegion struct are not changed, as
> they are all needed for usermode app implementation
> - region data is not taken from ram_list.blocks anymore, instead we
> use region data which is alredy calculated for use in vhost-net
> - Now multiple regions can have same FD and user applicaton can call
> mmap() multiple times with the same FD but with different offset
> (user needs to take care for offset page alignment)
>
> Signed-off-by: Damjan Marion <damar...@cisco.com>
> ---
> docs/specs/vhost-user.txt | 7 ++++---
> exec.c | 7 +++++++
> hw/virtio/vhost-user.c | 23 ++++++++++++++---------
> include/exec/ram_addr.h | 1 +
> 4 files changed, 26 insertions(+), 12 deletions(-)
>
> diff --git a/docs/specs/vhost-user.txt b/docs/specs/vhost-user.txt
> index 2641390..6abb697 100644
> --- a/docs/specs/vhost-user.txt
> +++ b/docs/specs/vhost-user.txt
> @@ -78,13 +78,14 @@ Depending on the request type, payload can be:
> Padding: 32-bit
>
> A region is:
> - ---------------------------------------
> - | guest address | size | user address |
> - ---------------------------------------
> + -----------------------------------------------------
> + | guest address | size | user address | mmap offset |
> + -----------------------------------------------------
>
> Guest address: a 64-bit guest address of the region
> Size: a 64-bit size
> User address: a 64-bit user address
> + mmmap offset: 64-bit offset where region starts in the mapped memory
mmap I guess?
>
>
> In QEMU the vhost-user message is implemented with the following struct:
> diff --git a/exec.c b/exec.c
> index c849405..a94c583 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -1456,6 +1456,13 @@ int qemu_get_ram_fd(ram_addr_t addr)
> return block->fd;
> }
>
> +void *qemu_get_ram_block_host_ptr(ram_addr_t addr)
> +{
> + RAMBlock *block = qemu_get_ram_block(addr);
> +
> + return block->host;
> +}
> +
> /* Return a host pointer to ram allocated with qemu_ram_alloc.
> With the exception of the softmmu code in this file, this should
> only be used for local memory (e.g. video ram) that the device owns,
> diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
> index 0df6a93..38e5806 100644
> --- a/hw/virtio/vhost-user.c
> +++ b/hw/virtio/vhost-user.c
> @@ -14,6 +14,7 @@
> #include "sysemu/kvm.h"
> #include "qemu/error-report.h"
> #include "qemu/sockets.h"
> +#include "exec/ram_addr.h"
>
> #include <fcntl.h>
> #include <unistd.h>
> @@ -47,6 +48,7 @@ typedef struct VhostUserMemoryRegion {
> uint64_t guest_phys_addr;
> uint64_t memory_size;
> uint64_t userspace_addr;
> + uint64_t mmap_offset;
> } VhostUserMemoryRegion;
>
> typedef struct VhostUserMemory {
> @@ -183,10 +185,10 @@ static int vhost_user_call(struct vhost_dev *dev,
> unsigned long int request,
> {
> VhostUserMsg msg;
> VhostUserRequest msg_request;
> - RAMBlock *block = 0;
> struct vhost_vring_file *file = 0;
> int need_reply = 0;
> int fds[VHOST_MEMORY_MAX_NREGIONS];
> + int i, fd;
> size_t fd_num = 0;
>
> assert(dev->vhost_ops->backend_type == VHOST_BACKEND_TYPE_USER);
> @@ -212,14 +214,17 @@ static int vhost_user_call(struct vhost_dev *dev,
> unsigned long int request,
> break;
>
> case VHOST_SET_MEM_TABLE:
> - QTAILQ_FOREACH(block, &ram_list.blocks, next)
> - {
> - if (block->fd > 0) {
> - msg.memory.regions[fd_num].userspace_addr =
> - (uintptr_t) block->host;
> - msg.memory.regions[fd_num].memory_size = block->length;
> - msg.memory.regions[fd_num].guest_phys_addr = block->offset;
> - fds[fd_num++] = block->fd;
> + for (i = 0; i < dev->mem->nregions; ++i) {
> + struct vhost_memory_region *reg = dev->mem->regions + i;
> + fd = qemu_get_ram_fd(reg->guest_phys_addr);
> + if (fd > 0) {
> + msg.memory.regions[fd_num].userspace_addr =
> reg->userspace_addr;
> + msg.memory.regions[fd_num].memory_size = reg->memory_size;
> + msg.memory.regions[fd_num].guest_phys_addr =
> reg->guest_phys_addr;
> + msg.memory.regions[fd_num].mmap_offset = reg->userspace_addr
> -
> + (uintptr_t)
> qemu_get_ram_block_host_ptr(reg->guest_phys_addr);
> + assert(fd_num < VHOST_MEMORY_MAX_NREGIONS);
> + fds[fd_num++] = fd;
> }
> }
>
> diff --git a/include/exec/ram_addr.h b/include/exec/ram_addr.h
> index 55ca676..e9eb831 100644
> --- a/include/exec/ram_addr.h
> +++ b/include/exec/ram_addr.h
> @@ -29,6 +29,7 @@ ram_addr_t qemu_ram_alloc_from_ptr(ram_addr_t size, void
> *host,
> MemoryRegion *mr);
> ram_addr_t qemu_ram_alloc(ram_addr_t size, MemoryRegion *mr);
> int qemu_get_ram_fd(ram_addr_t addr);
> +void *qemu_get_ram_block_host_ptr(ram_addr_t addr);
> void *qemu_get_ram_ptr(ram_addr_t addr);
> void qemu_ram_free(ram_addr_t addr);
> void qemu_ram_free_from_ptr(ram_addr_t addr);
> --
> 1.9.1
