From: Saurabh Sengar ssengar@linux.microsoft.com
[ Upstream commit 1d3e0980782fbafaf93285779fd3905e4f866802 ]
Current code is based on the idea that the max number of SGL entries also determines the max size of an I/O request. While this idea was true in older versions of the storvsc driver when SGL entry length was limited to 4 Kbytes, commit 3d9c3dcc58e9 ("scsi: storvsc: Enable scatterlist entry lengths > 4Kbytes") removed that limitation. It's now theoretically possible for the block layer to send requests that exceed the maximum size supported by Hyper-V. This problem doesn't currently happen in practice because the block layer defaults to a 512 Kbyte maximum, while Hyper-V in Azure supports 2 Mbyte I/O sizes. But some future configuration of Hyper-V could have a smaller max I/O size, and the block layer could exceed that max.
Fix this by correctly setting max_sectors as well as sg_tablesize to reflect the maximum I/O size that Hyper-V reports. While allowing I/O sizes larger than the block layer default of 512 Kbytes doesn’t provide any noticeable performance benefit in the tests we ran, it's still appropriate to report the correct underlying Hyper-V capabilities to the Linux block layer.
Also tweak the virt_boundary_mask to reflect that the required alignment derives from Hyper-V communication using a 4 Kbyte page size, and not on the guest page size, which might be bigger (eg. ARM64).
Link: https://lore.kernel.org/r/1655190355-28722-1-git-send-email-ssengar@linux.mi... Fixes: 3d9c3dcc58e9 ("scsi: storvsc: Enable scatter list entry lengths > 4Kbytes") Reviewed-by: Michael Kelley mikelley@microsoft.com Signed-off-by: Saurabh Sengar ssengar@linux.microsoft.com Signed-off-by: Martin K. Petersen martin.petersen@oracle.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/scsi/storvsc_drv.c | 27 ++++++++++++++++++++++----- 1 file changed, 22 insertions(+), 5 deletions(-)
diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c index 9eb1b88a29dd..71c7f7b435c4 100644 --- a/drivers/scsi/storvsc_drv.c +++ b/drivers/scsi/storvsc_drv.c @@ -1907,7 +1907,7 @@ static struct scsi_host_template scsi_driver = { .cmd_per_lun = 2048, .this_id = -1, /* Ensure there are no gaps in presented sgls */ - .virt_boundary_mask = PAGE_SIZE-1, + .virt_boundary_mask = HV_HYP_PAGE_SIZE - 1, .no_write_same = 1, .track_queue_depth = 1, .change_queue_depth = storvsc_change_queue_depth, @@ -1961,6 +1961,7 @@ static int storvsc_probe(struct hv_device *device, int max_targets; int max_channels; int max_sub_channels = 0; + u32 max_xfer_bytes;
/* * Based on the windows host we are running on, @@ -2049,12 +2050,28 @@ static int storvsc_probe(struct hv_device *device, } /* max cmd length */ host->max_cmd_len = STORVSC_MAX_CMD_LEN; - /* - * set the table size based on the info we got - * from the host. + * Any reasonable Hyper-V configuration should provide + * max_transfer_bytes value aligning to HV_HYP_PAGE_SIZE, + * protecting it from any weird value. + */ + max_xfer_bytes = round_down(stor_device->max_transfer_bytes, HV_HYP_PAGE_SIZE); + /* max_hw_sectors_kb */ + host->max_sectors = max_xfer_bytes >> 9; + /* + * There are 2 requirements for Hyper-V storvsc sgl segments, + * based on which the below calculation for max segments is + * done: + * + * 1. Except for the first and last sgl segment, all sgl segments + * should be align to HV_HYP_PAGE_SIZE, that also means the + * maximum number of segments in a sgl can be calculated by + * dividing the total max transfer length by HV_HYP_PAGE_SIZE. + * + * 2. Except for the first and last, each entry in the SGL must + * have an offset that is a multiple of HV_HYP_PAGE_SIZE. */ - host->sg_tablesize = (stor_device->max_transfer_bytes >> PAGE_SHIFT); + host->sg_tablesize = (max_xfer_bytes >> HV_HYP_PAGE_SHIFT) + 1; /* * For non-IDE disks, the host supports multiple channels. * Set the number of HW queues we are supporting.