Hyper-V provides Confidential VMBus to communicate between device model and device guest driver via encrypted/private memory in Confidential VM. The device model is in OpenHCL (https://openvmm.dev/guide/user_guide/openhcl.html) that plays the paravisor role.
For a VMBus device, there are two communication methods to talk with Host/Hypervisor. 1) VMBUS Ring buffer 2) Dynamic DMA transfer. The Confidential VMBus Ring buffer has been upstreamed by Roman Kisel(commit 6802d8af47d1). The dynamic DMA transition of VMBus device normally goes through DMA core and it uses SWIOTLB as bounce buffer in a CoCo VM. The Confidential VMBus device can do DMA directly to private/encrypted memory. Because the swiotlb is decrypted memory, the DMA transfer must not be bounced through the swiotlb, so as to preserve confidentiality. This is different from the default for Linux CoCo VMs, so not use DMA(SWIOTLB) API in VMBus driver when confidential dynamic DMA transfers capability is present. Signed-off-by: Tianyu Lan <[email protected]> --- Change since v1: * Fix code style issue * Use co_external_memory flag in struct vmbus_channel directly instead of adding new flag in the struct hv_device. --- drivers/scsi/storvsc_drv.c | 32 ++++++++++++++++++++++---------- 1 file changed, 22 insertions(+), 10 deletions(-) diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c index 6977ca8a0658..a3b22cba3421 100644 --- a/drivers/scsi/storvsc_drv.c +++ b/drivers/scsi/storvsc_drv.c @@ -1326,7 +1326,8 @@ static void storvsc_on_channel_callback(void *context) continue; } request = (struct storvsc_cmd_request *)scsi_cmd_priv(scmnd); - scsi_dma_unmap(scmnd); + if (!device->channel->co_external_memory) + scsi_dma_unmap(scmnd); } storvsc_on_receive(stor_device, packet, request); @@ -1815,7 +1816,7 @@ static enum scsi_qc_status storvsc_queuecommand(struct Scsi_Host *host, unsigned long offset_in_hvpg = offset_in_hvpage(sgl->offset); unsigned int hvpg_count = HVPFN_UP(offset_in_hvpg + length); struct scatterlist *sg; - unsigned long hvpfn, hvpfns_to_add; + unsigned long hvpfn, hvpfns_to_add, hvpgoff; int j, i = 0, sg_count; payload_sz = (hvpg_count * sizeof(u64) + @@ -1831,10 +1832,14 @@ static enum scsi_qc_status storvsc_queuecommand(struct Scsi_Host *host, payload->range.len = length; payload->range.offset = offset_in_hvpg; - sg_count = scsi_dma_map(scmnd); - if (sg_count < 0) { - ret = SCSI_MLQUEUE_DEVICE_BUSY; - goto err_free_payload; + if (dev->channel->co_external_memory) { + sg_count = scsi_sg_count(scmnd); + } else { + sg_count = scsi_dma_map(scmnd); + if (sg_count < 0) { + ret = SCSI_MLQUEUE_DEVICE_BUSY; + goto err_free_payload; + } } for_each_sg(sgl, sg, sg_count, j) { @@ -1846,9 +1851,16 @@ static enum scsi_qc_status storvsc_queuecommand(struct Scsi_Host *host, * Such offsets are handled even on other than the first * sgl entry, provided they are a multiple of PAGE_SIZE. */ - hvpfn = HVPFN_DOWN(sg_dma_address(sg)); - hvpfns_to_add = HVPFN_UP(sg_dma_address(sg) + - sg_dma_len(sg)) - hvpfn; + if (dev->channel->co_external_memory) { + hvpgoff = HVPFN_DOWN(sg->offset); + hvpfn = page_to_hvpfn(sg_page(sg)) + hvpgoff; + hvpfns_to_add = HVPFN_UP(sg->offset + sg->length) - + hvpgoff; + } else { + hvpfn = HVPFN_DOWN(sg_dma_address(sg)); + hvpfns_to_add = HVPFN_UP(sg_dma_address(sg) + + sg_dma_len(sg)) - hvpfn; + } /* * Fill the next portion of the PFN array with @@ -1870,7 +1882,7 @@ static enum scsi_qc_status storvsc_queuecommand(struct Scsi_Host *host, ret = storvsc_do_io(dev, cmd_request, smp_processor_id()); migrate_enable(); - if (ret) + if (ret && (!dev->channel->co_external_memory)) scsi_dma_unmap(scmnd); if (ret == -EAGAIN) { -- 2.50.1
