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Subject[PATCH v4 11/11] scsi: storvsc: Support PAGE_SIZE larger than 4K
Date
Hyper-V always use 4k page size (HV_HYP_PAGE_SIZE), so when
communicating with Hyper-V, a guest should always use HV_HYP_PAGE_SIZE
as the unit for page related data. For storvsc, the data is
vmbus_packet_mpb_array. And since in scsi_cmnd, sglist of pages (in unit
of PAGE_SIZE) is used, we need convert pages in the sglist of scsi_cmnd
into Hyper-V pages in vmbus_packet_mpb_array.

This patch does the conversion by dividing pages in sglist into Hyper-V
pages, offset and indexes in vmbus_packet_mpb_array are recalculated
accordingly.

Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
---
drivers/scsi/storvsc_drv.c | 56 +++++++++++++++++++++++++++++++++-----
1 file changed, 49 insertions(+), 7 deletions(-)

diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
index 8f5f5dc863a4..0c65fbd41035 100644
--- a/drivers/scsi/storvsc_drv.c
+++ b/drivers/scsi/storvsc_drv.c
@@ -1739,23 +1739,65 @@ static int storvsc_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *scmnd)
payload_sz = sizeof(cmd_request->mpb);

if (sg_count) {
- if (sg_count > MAX_PAGE_BUFFER_COUNT) {
+ unsigned int hvpgoff = 0;
+ unsigned long offset_in_hvpg = sgl->offset & ~HV_HYP_PAGE_MASK;
+ unsigned int hvpg_count = HVPFN_UP(offset_in_hvpg + length);
+ u64 hvpfn;

- payload_sz = (sg_count * sizeof(u64) +
+ if (hvpg_count > MAX_PAGE_BUFFER_COUNT) {
+
+ payload_sz = (hvpg_count * sizeof(u64) +
sizeof(struct vmbus_packet_mpb_array));
payload = kzalloc(payload_sz, GFP_ATOMIC);
if (!payload)
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 = sgl[0].offset;
+ payload->range.offset = offset_in_hvpg;
+ hvpgoff = sgl->offset >> HV_HYP_PAGE_SHIFT;

cur_sgl = sgl;
- for (i = 0; i < sg_count; i++) {
- payload->range.pfn_array[i] =
- page_to_pfn(sg_page((cur_sgl)));
- cur_sgl = sg_next(cur_sgl);
+ for (i = 0; i < hvpg_count; i++) {
+ /*
+ * '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 ---------------------------+
+ */
+ unsigned int hvpgoff_in_page =
+ (i + hvpgoff) % NR_HV_HYP_PAGES_IN_PAGE;
+
+ /*
+ * 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.
+ */
+ 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;
}
}

--
2.28.0
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