Commit 3d9c3dcc authored by Michael Kelley's avatar Michael Kelley Committed by Martin K. Petersen
Browse files

scsi: storvsc: Enable scatterlist entry lengths > 4Kbytes 

storvsc currently sets .dma_boundary to limit scatterlist entries to 4
Kbytes, which is less efficient with huge pages that offer large chunks of
contiguous physical memory. Improve the algorithm for creating the Hyper-V
guest physical address PFN array so that scatterlist entries with lengths >
4Kbytes are handled.  As a result, remove the .dma_boundary setting.

The improved algorithm also adds support for scatterlist entries with
offsets >= 4Kbytes, which is supported by many other SCSI low-level
drivers.  And it retains support for architectures where possibly PAGE_SIZE
!= HV_HYP_PAGE_SIZE (such as ARM64).

Link: https://lore.kernel.org/r/1614120294-1930-1-git-send-email-mikelley@microsoft.com


Reviewed-by: default avatarVitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: default avatarMichael Kelley <mikelley@microsoft.com>
Signed-off-by: default avatarMartin K. Petersen <martin.petersen@oracle.com>
parent 471ee95c

drivers/scsi/storvsc_drv.c

+23 −43
Original line number Diff line number Diff line
@@ -1692,9 +1692,8 @@ static int storvsc_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *scmnd) 
	struct storvsc_cmd_request *cmd_request = scsi_cmd_priv(scmnd);

	int i;

	struct scatterlist *sgl;

	unsigned int sg_count = 0;

	unsigned int sg_count;

	struct vmscsi_request *vm_srb;

	struct scatterlist *cur_sgl;

	struct vmbus_packet_mpb_array  *payload;

	u32 payload_sz;

	u32 length;
@@ -1773,8 +1772,8 @@ static int storvsc_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *scmnd) 
	payload_sz = sizeof(cmd_request->mpb);



	if (sg_count) {

		unsigned int hvpgoff = 0;

		unsigned long offset_in_hvpg = sgl->offset & ~HV_HYP_PAGE_MASK;

		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;
@@ -1787,51 +1786,34 @@ static int storvsc_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *scmnd) 
				return SCSI_MLQUEUE_DEVICE_BUSY;

		}



		/*

		 * sgl is a list of PAGEs, and payload->range.pfn_array

		 * expects the page number in the unit of HV_HYP_PAGE_SIZE (the

		 * page size that Hyper-V uses, so here we need to divide PAGEs

		 * into HV_HYP_PAGE in case that PAGE_SIZE > HV_HYP_PAGE_SIZE.

		 * Besides, payload->range.offset should be the offset in one

		 * HV_HYP_PAGE.

		 */

		payload->range.len = length;

		payload->range.offset = offset_in_hvpg;

		hvpgoff = sgl->offset >> HV_HYP_PAGE_SHIFT;



		cur_sgl = sgl;

		for (i = 0; i < hvpg_count; i++) {



		for (i = 0; sgl != NULL; sgl = sg_next(sgl)) {

			/*

			 * 'i' is the index of hv pages in the payload and

			 * 'hvpgoff' is the offset (in hv pages) of the first

			 * hv page in the the first page. The relationship

			 * between the sum of 'i' and 'hvpgoff' and the offset

			 * (in hv pages) in a payload page ('hvpgoff_in_page')

			 * is as follow:

			 *

			 * |------------------ PAGE -------------------|

			 * |   NR_HV_HYP_PAGES_IN_PAGE hvpgs in total  |

			 * |hvpg|hvpg| ...              |hvpg|... |hvpg|

			 * ^         ^                                 ^                 ^

			 * +-hvpgoff-+                                 +-hvpgoff_in_page-+

			 *           ^                                                   |

			 *           +--------------------- i ---------------------------+

			 * 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.

			 */

			unsigned int hvpgoff_in_page =

				(i + hvpgoff) % NR_HV_HYP_PAGES_IN_PAGE;

			hvpgoff = HVPFN_DOWN(sgl->offset);

			hvpfn = page_to_hvpfn(sg_page(sgl)) + hvpgoff;

			hvpfns_to_add =	HVPFN_UP(sgl->offset + sgl->length) -

						hvpgoff;



			/*

			 * Two cases that we need to fetch a page:

			 * 1) i == 0, the first step or

			 * 2) hvpgoff_in_page == 0, when we reach the boundary

			 *    of a page.

			 * Fill the next portion of the PFN array with

			 * sequential Hyper-V PFNs for the continguous physical

			 * memory described by the sgl entry. The end of the

			 * last sgl should be reached at the same time that

			 * the PFN array is filled.

			 */

			if (hvpgoff_in_page == 0 || i == 0) {

				hvpfn = page_to_hvpfn(sg_page(cur_sgl));

				cur_sgl = sg_next(cur_sgl);

			}



			payload->range.pfn_array[i] = hvpfn + hvpgoff_in_page;

			while (hvpfns_to_add--)

				payload->range.pfn_array[i++] =	hvpfn++;

		}

	}
@@ -1865,8 +1847,6 @@ static struct scsi_host_template scsi_driver = { 
	.slave_configure =	storvsc_device_configure,

	.cmd_per_lun =		2048,

	.this_id =		-1,

	/* Make sure we dont get a sg segment crosses a page boundary */

	.dma_boundary =		PAGE_SIZE-1,

	/* Ensure there are no gaps in presented sgls */

	.virt_boundary_mask =	PAGE_SIZE-1,

	.no_write_same =	1,

include/linux/hyperv.h

+1 −0
Original line number Diff line number Diff line
@@ -1726,6 +1726,7 @@ static inline unsigned long virt_to_hvpfn(void *addr) 
#define NR_HV_HYP_PAGES_IN_PAGE	(PAGE_SIZE / HV_HYP_PAGE_SIZE)

#define offset_in_hvpage(ptr)	((unsigned long)(ptr) & ~HV_HYP_PAGE_MASK)

#define HVPFN_UP(x)	(((x) + HV_HYP_PAGE_SIZE-1) >> HV_HYP_PAGE_SHIFT)

#define HVPFN_DOWN(x)	((x) >> HV_HYP_PAGE_SHIFT)

#define page_to_hvpfn(page)	(page_to_pfn(page) * NR_HV_HYP_PAGES_IN_PAGE)



#endif /* _HYPERV_H */