RE: [PATCH V6 4/5] scsi: storvsc: Add Isolation VM support for storvsc driver

Long Li
2021-12-09T08:00:38Z

> Subject: [PATCH V6 4/5] scsi: storvsc: Add Isolation VM support for storvsc driver
>
> From: Tianyu Lan <Tianyu.Lan@microsoft.com>
>
> In Isolation VM, all shared memory with host needs to mark visible to host via
> hvcall. vmbus_establish_gpadl() has already done it for storvsc rx/tx ring buffer.
> The page buffer used by vmbus_sendpacket_
> mpb_desc() still needs to be handled. Use DMA API(scsi_dma_map/unmap) to
> map these memory during sending/receiving packet and return swiotlb bounce
> buffer dma address. In Isolation VM, swiotlb bounce buffer is marked to be
> visible to host and the swiotlb force mode is enabled.
>
> Set device's dma min align mask to HV_HYP_PAGE_SIZE - 1 in order to keep the
> original data offset in the bounce buffer.
>
> Signed-off-by: Tianyu Lan <Tianyu.Lan@microsoft.com>
> ---
> drivers/hv/vmbus_drv.c | 4 ++++
> drivers/scsi/storvsc_drv.c | 37 +++++++++++++++++++++----------------
> include/linux/hyperv.h | 1 +
> 3 files changed, 26 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c index
> 392c1ac4f819..ae6ec503399a 100644
> --- a/drivers/hv/vmbus_drv.c
> +++ b/drivers/hv/vmbus_drv.c
> @@ -33,6 +33,7 @@
> #include <linux/random.h>
> #include <linux/kernel.h>
> #include <linux/syscore_ops.h>
> +#include <linux/dma-map-ops.h>
> #include <clocksource/hyperv_timer.h>
> #include "hyperv_vmbus.h"
>
> @@ -2078,6 +2079,7 @@ struct hv_device *vmbus_device_create(const guid_t
> *type,
> return child_device_obj;
> }
>
> +static u64 vmbus_dma_mask = DMA_BIT_MASK(64);
> /*
> * vmbus_device_register - Register the child device
> */
> @@ -2118,6 +2120,8 @@ int vmbus_device_register(struct hv_device
> *child_device_obj)
> }
> hv_debug_add_dev_dir(child_device_obj);
>
> + child_device_obj->device.dma_mask = &vmbus_dma_mask;
> + child_device_obj->device.dma_parms = &child_device_obj->dma_parms;
> return 0;
>
> err_kset_unregister:
> diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c index
> 20595c0ba0ae..ae293600d799 100644
> --- a/drivers/scsi/storvsc_drv.c
> +++ b/drivers/scsi/storvsc_drv.c
> @@ -21,6 +21,8 @@
> #include <linux/device.h>
> #include <linux/hyperv.h>
> #include <linux/blkdev.h>
> +#include <linux/dma-mapping.h>
> +
> #include <scsi/scsi.h>
> #include <scsi/scsi_cmnd.h>
> #include <scsi/scsi_host.h>
> @@ -1336,6 +1338,7 @@ static void storvsc_on_channel_callback(void
> *context)
> continue;
> }
> request = (struct storvsc_cmd_request
> *)scsi_cmd_priv(scmnd);
> + scsi_dma_unmap(scmnd);
> }
>
> storvsc_on_receive(stor_device, packet, request); @@
> -1749,7 +1752,6 @@ static int storvsc_queuecommand(struct Scsi_Host *host,
> struct scsi_cmnd *scmnd)
> struct hv_host_device *host_dev = shost_priv(host);
> struct hv_device *dev = host_dev->dev;
> struct storvsc_cmd_request *cmd_request = scsi_cmd_priv(scmnd);
> - int i;
> struct scatterlist *sgl;
> unsigned int sg_count;
> struct vmscsi_request *vm_srb;
> @@ -1831,10 +1833,11 @@ static int storvsc_queuecommand(struct Scsi_Host
> *host, struct scsi_cmnd *scmnd)
> payload_sz = sizeof(cmd_request->mpb);
>
> if (sg_count) {
> - unsigned int hvpgoff, hvpfns_to_add;
> unsigned long offset_in_hvpg = offset_in_hvpage(sgl->offset);
> unsigned int hvpg_count = HVPFN_UP(offset_in_hvpg + length);
> - u64 hvpfn;
> + struct scatterlist *sg;
> + unsigned long hvpfn, hvpfns_to_add;
> + int j, i = 0;
>
> if (hvpg_count > MAX_PAGE_BUFFER_COUNT) {
>
> @@ -1848,21 +1851,22 @@ static int storvsc_queuecommand(struct Scsi_Host
> *host, struct scsi_cmnd *scmnd)
> payload->range.len = length;
> payload->range.offset = offset_in_hvpg;
>
> + sg_count = scsi_dma_map(scmnd);
> + if (sg_count < 0)
> + return SCSI_MLQUEUE_DEVICE_BUSY;

Hi Tianyu,

This patch (and this patch series) unconditionally adds code for dealing with DMA addresses for all VMs, including non-isolation VMs.

Does this add performance penalty for VMs that don't require isolation?

Long

>
> - for (i = 0; sgl != NULL; sgl = sg_next(sgl)) {
> + for_each_sg(sgl, sg, sg_count, j) {
> /*
> - * Init values for the current sgl entry. hvpgoff
> - * and hvpfns_to_add are in units of Hyper-V size
> - * pages. Handling the PAGE_SIZE !=
> HV_HYP_PAGE_SIZE
> - * case also handles values of sgl->offset that are
> - * larger than PAGE_SIZE. Such offsets are handled
> - * even on other than the first sgl entry, provided
> - * they are a multiple of PAGE_SIZE.
> + * Init values for the current sgl entry. hvpfns_to_add
> + * is in units of Hyper-V size pages. Handling the
> + * PAGE_SIZE != HV_HYP_PAGE_SIZE case also handles
> + * values of sgl->offset that are larger than PAGE_SIZE.
> + * Such offsets are handled even on other than the first
> + * sgl entry, provided they are a multiple of PAGE_SIZE.
> */
> - hvpgoff = HVPFN_DOWN(sgl->offset);
> - hvpfn = page_to_hvpfn(sg_page(sgl)) + hvpgoff;
> - hvpfns_to_add = HVPFN_UP(sgl->offset + sgl-
> >length) -
> - hvpgoff;
> + 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 @@ -
> 1872,7 +1876,7 @@ static int storvsc_queuecommand(struct Scsi_Host *host,
> struct scsi_cmnd *scmnd)
> * the PFN array is filled.
> */
> while (hvpfns_to_add--)
> - payload->range.pfn_array[i++] = hvpfn++;
> + payload->range.pfn_array[i++] = hvpfn++;
> }
> }
>
> @@ -2016,6 +2020,7 @@ static int storvsc_probe(struct hv_device *device,
> stor_device->vmscsi_size_delta = sizeof(struct vmscsi_win8_extension);
> spin_lock_init(&stor_device->lock);
> hv_set_drvdata(device, stor_device);
> + dma_set_min_align_mask(&device->device, HV_HYP_PAGE_SIZE - 1);
>
> stor_device->port_number = host->host_no;
> ret = storvsc_connect_to_vsp(device, storvsc_ringbuffer_size, is_fc);
> diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h index
> 1f037e114dc8..74f5e92f91a0 100644
> --- a/include/linux/hyperv.h
> +++ b/include/linux/hyperv.h
> @@ -1261,6 +1261,7 @@ struct hv_device {
>
> struct vmbus_channel *channel;
> struct kset *channels_kset;
> + struct device_dma_parameters dma_parms;
>
> /* place holder to keep track of the dir for hv device in debugfs */
> struct dentry *debug_dir;
> --
> 2.25.1