linux-kernel - [RFC 11/11] scsi: storvsc: Support PAGE

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Date:   Tue, 21 Jul 2020 09:41:35 +0800
From:   Boqun Feng <boqun.feng@...il.com>
To:     linux-hyperv@...r.kernel.org, linux-input@...r.kernel.org,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        linux-scsi@...r.kernel.org
Cc:     "K. Y. Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Wei Liu <wei.liu@...nel.org>, Jiri Kosina <jikos@...nel.org>,
        Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Michael Kelley <mikelley@...rosoft.com>,
        Boqun Feng <boqun.feng@...il.com>
Subject: [RFC 11/11] scsi: storvsc: Support PAGE_SIZE larger than 4K

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@...il.com>
---
 drivers/scsi/storvsc_drv.c | 27 +++++++++++++++++++++------
 1 file changed, 21 insertions(+), 6 deletions(-)

diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
index fb41636519ee..c54d25f279bc 100644
--- a/drivers/scsi/storvsc_drv.c
+++ b/drivers/scsi/storvsc_drv.c
@@ -1561,7 +1561,7 @@ 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;
+	int i, j, k;
 	struct scatterlist *sgl;
 	unsigned int sg_count = 0;
 	struct vmscsi_request *vm_srb;
@@ -1569,6 +1569,8 @@ static int storvsc_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *scmnd)
 	struct vmbus_packet_mpb_array  *payload;
 	u32 payload_sz;
 	u32 length;
+	int subpage_idx = 0;
+	unsigned int hvpg_count = 0;
 
 	if (vmstor_proto_version <= VMSTOR_PROTO_VERSION_WIN8) {
 		/*
@@ -1643,23 +1645,36 @@ 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) {
+		hvpg_count = sg_count * (PAGE_SIZE / HV_HYP_PAGE_SIZE);
+		if (hvpg_count > MAX_PAGE_BUFFER_COUNT) {
 
-			payload_sz = (sg_count * sizeof(u64) +
+			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.
+		 */
 		payload->range.len = length;
-		payload->range.offset = sgl[0].offset;
+		payload->range.offset = sgl[0].offset & ~HV_HYP_PAGE_MASK;
+		subpage_idx = sgl[0].offset >> HV_HYP_PAGE_SHIFT;
 
 		cur_sgl = sgl;
+		k = 0;
 		for (i = 0; i < sg_count; i++) {
-			payload->range.pfn_array[i] =
-				page_to_pfn(sg_page((cur_sgl)));
+			for (j = subpage_idx; j < (PAGE_SIZE / HV_HYP_PAGE_SIZE); j++) {
+				payload->range.pfn_array[k] =
+					page_to_hvpfn(sg_page((cur_sgl))) + j;
+				k++;
+			}
 			cur_sgl = sg_next(cur_sgl);
+			subpage_idx = 0;
 		}
 	}
 
-- 
2.27.0