RE: [PATCH v4] vhost: fix physical address mapping

["Ding, Xuan" <xuan.ding@intel.com>]

Hi Maxime,

>-----Original Message-----
>From: Ding, Xuan <xuan.ding@intel.com>
>Sent: Tuesday, November 16, 2021 4:24 PM
>To: Xia, Chenbo <chenbo.xia@intel.com>; maxime.coquelin@redhat.com
>Cc: dev@dpdk.org; Hu, Jiayu <jiayu.hu@intel.com>; Wang, YuanX
><yuanx.wang@intel.com>; He, Xingguang <xingguang.he@intel.com>
>Subject: RE: [PATCH v4] vhost: fix physical address mapping
>
>Hi Chenbo,
>
>> -----Original Message-----
>> From: Xia, Chenbo <chenbo.xia@intel.com>
>> Sent: 2021年11月16日 15:48
>> To: Ding, Xuan <xuan.ding@intel.com>; maxime.coquelin@redhat.com
>> Cc: dev@dpdk.org; Hu, Jiayu <jiayu.hu@intel.com>; Wang, YuanX
>> <yuanx.wang@intel.com>; He, Xingguang <xingguang.he@intel.com>
>> Subject: RE: [PATCH v4] vhost: fix physical address mapping
>>
>> > -----Original Message-----
>> > From: Ding, Xuan <xuan.ding@intel.com>
>> > Sent: Monday, November 15, 2021 8:32 PM
>> > To: maxime.coquelin@redhat.com; Xia, Chenbo <chenbo.xia@intel.com>
>> > Cc: dev@dpdk.org; Hu, Jiayu <jiayu.hu@intel.com>; Wang, YuanX
>> > <yuanx.wang@intel.com>; He, Xingguang <xingguang.he@intel.com>;
>> > Ding, Xuan <xuan.ding@intel.com>
>> > Subject: [PATCH v4] vhost: fix physical address mapping
>> >
>> > When choosing IOVA as PA mode, IOVA is likely to be discontinuous,
>> > which requires page by page mapping for DMA devices. To be
>> > consistent, this patch implements page by page mapping instead of
>> > mapping at the region granularity for both IOVA as VA and PA mode.
>> >
>> > Fixes: 7c61fa08b716 ("vhost: enable IOMMU for async vhost")
>> >
>> > Signed-off-by: Xuan Ding <xuan.ding@intel.com>
>> > ---
>> > v4:
>> > * Remove unnessary ENOSUP check.
>> > * Adjust return type.
>> >
>> > v3:
>> > * Fix commit title.
>> >
>> > v2:
>> > * Fix a format issue.
>> > ---
>> >  lib/vhost/vhost.h      |   1 +
>> >  lib/vhost/vhost_user.c | 111
>> > ++++++++++++++++++++---------------------
>> >  2 files changed, 54 insertions(+), 58 deletions(-)
>> >
>> > diff --git a/lib/vhost/vhost.h b/lib/vhost/vhost.h index
>> > 7085e0885c..d246538ca5 100644
>> > --- a/lib/vhost/vhost.h
>> > +++ b/lib/vhost/vhost.h
>> > @@ -355,6 +355,7 @@ struct vring_packed_desc_event {  struct
>> > guest_page {
>> >  	uint64_t guest_phys_addr;
>> >  	uint64_t host_phys_addr;
>>
>> This name confused me when doing review: this should be host_iova.
>>
>> Could you help rename it in the patch?
>
>Yes, the host_phys_addr is a iova, it depends on the DPDK IOVA mode.
>
>>
>> > +	uint64_t host_user_addr;
>> >  	uint64_t size;
>> >  };
>> >
>> > diff --git a/lib/vhost/vhost_user.c b/lib/vhost/vhost_user.c index
>> > a781346c4d..0a9dc3350f 100644
>> > --- a/lib/vhost/vhost_user.c
>> > +++ b/lib/vhost/vhost_user.c
>> > @@ -143,57 +143,56 @@ get_blk_size(int fd)
>> >  	return ret == -1 ? (uint64_t)-1 : (uint64_t)stat.st_blksize;  }
>> >
>> > -static int
>> > -async_dma_map(struct rte_vhost_mem_region *region, bool do_map)
>> > +static void
>> > +async_dma_map(struct virtio_net *dev, bool do_map)
>> >  {
>> > -	uint64_t host_iova;
>> >  	int ret = 0;
>> > -
>> > -	host_iova = rte_mem_virt2iova((void *)(uintptr_t)region-
>> >host_user_addr);
>> > +	uint32_t i;
>> > +	struct guest_page *page;
>> >  	if (do_map) {
>> > -		/* Add mapped region into the default container of DPDK. */
>> > -		ret =
>> rte_vfio_container_dma_map(RTE_VFIO_DEFAULT_CONTAINER_FD,
>> > -						 region->host_user_addr,
>> > -						 host_iova,
>> > -						 region->size);
>> > -		if (ret) {
>> > -			/*
>> > -			 * DMA device may bind with kernel driver, in this case,
>> > -			 * we don't need to program IOMMU manually.
>> However, if no
>> > -			 * device is bound with vfio/uio in DPDK, and vfio
>kernel
>> > -			 * module is loaded, the API will still be called and
>> return
>> > -			 * with ENODEV/ENOSUP.
>> > -			 *
>> > -			 * DPDK vfio only returns ENODEV/ENOSUP in very
>> similar
>> > -			 * situations(vfio either unsupported, or supported
>> > -			 * but no devices found). Either way, no mappings
>could
>> be
>> > -			 * performed. We treat it as normal case in async path.
>> > -			 */
>> > -			if (rte_errno == ENODEV || rte_errno == ENOTSUP)
>> > -				return 0;
>> > -
>> > -			VHOST_LOG_CONFIG(ERR, "DMA engine map
>failed\n");
>> > -			/* DMA mapping errors won't stop
>> VHST_USER_SET_MEM_TABLE. */
>> > -			return 0;
>> > +		for (i = 0; i < dev->nr_guest_pages; i++) {
>> > +			page = &dev->guest_pages[i];
>> > +			ret =
>> > rte_vfio_container_dma_map(RTE_VFIO_DEFAULT_CONTAINER_FD,
>> > +							 page-
>> >host_user_addr,
>> > +							 page-
>> >host_phys_addr,
>> > +							 page->size);
>> > +			if (ret) {
>> > +				/*
>> > +				 * DMA device may bind with kernel driver, in
>> this
>> > case,
>> > +				 * we don't need to program IOMMU manually.
>> However,
>> > if no
>> > +				 * device is bound with vfio/uio in DPDK, and
>> vfio
>> > kernel
>> > +				 * module is loaded, the API will still be called
>> and
>> > return
>> > +				 * with ENODEV.
>> > +				 *
>> > +				 * DPDK vfio only returns ENODEV in very
>> similar
>> > situations
>> > +				 * (vfio either unsupported, or supported but
>no
>> > devices found).
>> > +				 * Either way, no mappings could be
>performed.
>> We
>> > treat it as
>> > +				 * normal case in async path. This is a
>> workaround.
>> > +				 */
>> > +				if (rte_errno == ENODEV)
>> > +					return;
>> > +
>> > +				/* DMA mapping errors won't stop
>> > VHST_USER_SET_MEM_TABLE. */
>>
>> A comment in v3 is missed:
>
>Thanks for the catch. Will fix it in v5.
>
>Thanks,
>Xuan

After off list discussion with Yuan, this patch has dependency on Yuan's fix patch.
And it should also take the HVA continuity into consideration. Since the v21.11 merge window is almost closed,
we plan to merge the two patches and send it in next release, does it make sense for you?

Sorry for missing some test cases under PA mode, which requires some changes for the current design.

Thanks,
Xuan

>
>>
>> VHST -> VHOST
>>
>> Thanks,
>> Chenbo
>>
>> > +				VHOST_LOG_CONFIG(ERR, "DMA engine map
>> failed\n");
>> > +			}
>> >  		}
>> >
>> >  	} else {
>> > -		/* Remove mapped region from the default container of DPDK.
>> */
>> > -		ret =
>> rte_vfio_container_dma_unmap(RTE_VFIO_DEFAULT_CONTAINER_FD,
>> > -						   region->host_user_addr,
>> > -						   host_iova,
>> > -						   region->size);
>> > -		if (ret) {
>> > -			/* like DMA map, ignore the kernel driver case when
>> unmap.
>> > */
>> > -			if (rte_errno == EINVAL)
>> > -				return 0;
>> > -
>> > -			VHOST_LOG_CONFIG(ERR, "DMA engine unmap
>> failed\n");
>> > -			return ret;
>> > +		for (i = 0; i < dev->nr_guest_pages; i++) {
>> > +			page = &dev->guest_pages[i];
>> > +			ret =
>> > rte_vfio_container_dma_unmap(RTE_VFIO_DEFAULT_CONTAINER_FD,
>> > +							   page-
>> >host_user_addr,
>> > +							   page-
>> >host_phys_addr,
>> > +							   page->size);
>> > +			if (ret) {
>> > +				/* like DMA map, ignore the kernel driver case
>> when
>> > unmap. */
>> > +				if (rte_errno == EINVAL)
>> > +					return;
>> > +
>> > +				VHOST_LOG_CONFIG(ERR, "DMA engine
>> unmap failed\n");
>> > +			}
>> >  		}
>> >  	}
>> > -
>> > -	return ret;
>> >  }
>> >
>> >  static void
>> > @@ -205,12 +204,12 @@ free_mem_region(struct virtio_net *dev)
>> >  	if (!dev || !dev->mem)
>> >  		return;
>> >
>> > +	if (dev->async_copy && rte_vfio_is_enabled("vfio"))
>> > +		async_dma_map(dev, false);
>> > +
>> >  	for (i = 0; i < dev->mem->nregions; i++) {
>> >  		reg = &dev->mem->regions[i];
>> >  		if (reg->host_user_addr) {
>> > -			if (dev->async_copy && rte_vfio_is_enabled("vfio"))
>> > -				async_dma_map(reg, false);
>> > -
>> >  			munmap(reg->mmap_addr, reg->mmap_size);
>> >  			close(reg->fd);
>> >  		}
>> > @@ -978,7 +977,7 @@ vhost_user_set_vring_base(struct virtio_net
>> > **pdev,
>> >
>> >  static int
>> >  add_one_guest_page(struct virtio_net *dev, uint64_t guest_phys_addr,
>> > -		   uint64_t host_phys_addr, uint64_t size)
>> > +		   uint64_t host_phys_addr, uint64_t host_user_addr, uint64_t
>> size)
>> >  {
>> >  	struct guest_page *page, *last_page;
>> >  	struct guest_page *old_pages;
>> > @@ -1009,6 +1008,7 @@ add_one_guest_page(struct virtio_net *dev,
>> > uint64_t guest_phys_addr,
>> >  	page = &dev->guest_pages[dev->nr_guest_pages++];
>> >  	page->guest_phys_addr = guest_phys_addr;
>> >  	page->host_phys_addr  = host_phys_addr;
>> > +	page->host_user_addr = host_user_addr;
>> >  	page->size = size;
>> >
>> >  	return 0;
>> > @@ -1028,7 +1028,8 @@ add_guest_pages(struct virtio_net *dev, struct
>> > rte_vhost_mem_region *reg,
>> >  	size = page_size - (guest_phys_addr & (page_size - 1));
>> >  	size = RTE_MIN(size, reg_size);
>> >
>> > -	if (add_one_guest_page(dev, guest_phys_addr, host_phys_addr, size)
><
>> 0)
>> > +	if (add_one_guest_page(dev, guest_phys_addr, host_phys_addr,
>> > +			       host_user_addr, size) < 0)
>> >  		return -1;
>> >
>> >  	host_user_addr  += size;
>> > @@ -1040,7 +1041,7 @@ add_guest_pages(struct virtio_net *dev, struct
>> > rte_vhost_mem_region *reg,
>> >  		host_phys_addr = rte_mem_virt2iova((void *)(uintptr_t)
>> >  						  host_user_addr);
>> >  		if (add_one_guest_page(dev, guest_phys_addr,
>host_phys_addr,
>> > -				size) < 0)
>> > +				       host_user_addr, size) < 0)
>> >  			return -1;
>> >
>> >  		host_user_addr  += size;
>> > @@ -1215,7 +1216,6 @@ vhost_user_mmap_region(struct virtio_net *dev,
>> >  	uint64_t mmap_size;
>> >  	uint64_t alignment;
>> >  	int populate;
>> > -	int ret;
>> >
>> >  	/* Check for memory_size + mmap_offset overflow */
>> >  	if (mmap_offset >= -region->size) { @@ -1274,14 +1274,6 @@
>> > vhost_user_mmap_region(struct virtio_net *dev,
>> >  			VHOST_LOG_CONFIG(ERR, "adding guest pages to
>> region failed.\n");
>> >  			return -1;
>> >  		}
>> > -
>> > -		if (rte_vfio_is_enabled("vfio")) {
>> > -			ret = async_dma_map(region, true);
>> > -			if (ret) {
>> > -				VHOST_LOG_CONFIG(ERR, "Configure IOMMU
>> for DMA engine
>> > failed\n");
>> > -				return -1;
>> > -			}
>> > -		}
>> >  	}
>> >
>> >  	VHOST_LOG_CONFIG(INFO,
>> > @@ -1420,6 +1412,9 @@ vhost_user_set_mem_table(struct virtio_net
>> > **pdev, struct VhostUserMsg *msg,
>> >  		dev->mem->nregions++;
>> >  	}
>> >
>> > +	if (dev->async_copy && rte_vfio_is_enabled("vfio"))
>> > +		async_dma_map(dev, true);
>> > +
>> >  	if (vhost_user_postcopy_register(dev, main_fd, msg) < 0)
>> >  		goto free_mem_table;
>> >
>> > --
>> > 2.17.1