Michael Kelley <mikelley@xxxxxxxxxxxxx> writes:
> 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).
>
> Signed-off-by: Michael Kelley <mikelley@xxxxxxxxxxxxx>
> ---
>
> Changes in v2:
> * Add HVPFN_DOWN() macro and use it instead of open coding
> [Vitaly Kuznetsov]
> * Change loop that fills pfn array and its initialization
> [Vitaly Kuznetsov]
> * Use offset_in_hvpage() instead of open coding
>
>
> drivers/scsi/storvsc_drv.c | 66 ++++++++++++++++------------------------------
> include/linux/hyperv.h | 1 +
> 2 files changed, 24 insertions(+), 43 deletions(-)
>
> diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
> index 2e4fa77..5ba3145 100644
> --- a/drivers/scsi/storvsc_drv.c
> +++ b/drivers/scsi/storvsc_drv.c
> @@ -1678,9 +1678,8 @@ 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;
> @@ -1759,8 +1758,8 @@ 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;
>
> @@ -1773,51 +1772,34 @@ 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++;
> }
> }
>
> @@ -1851,8 +1833,6 @@ static int storvsc_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *scmnd)
> .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,
> diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
> index 5ddb479..a1eed76 100644
> --- a/include/linux/hyperv.h
> +++ b/include/linux/hyperv.h
> @@ -1717,6 +1717,7 @@ 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 */
Thank you for implementing my suggestion in v2,
Reviewed-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
--
Vitaly
