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scsi: storvsc: Enable scatterlist entry lengths > 4Kbytes

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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: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Michael Kelley <mikelley@microsoft.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
This commit is contained in:
Michael Kelley 2021-02-23 14:44:54 -08:00 committed by Martin K. Petersen
parent 471ee95ccc
commit 3d9c3dcc58
2 changed files with 24 additions and 43 deletions
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66
drivers/scsi/storvsc_drv.c
View file

@ -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,

1
include/linux/hyperv.h
View file

@ -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 */