On Thu, 2018-09-06 at 13:37 -0700, Xuewei Zhang wrote: +AD4 Currently a scsi device won't contribute to kernel randomness when it +AD4 uses blk-mq. Since we commonly use scsi on rotational device with +AD4 blk-mq, it make sense to keep contributing to kernel randomness in these +AD4 cases. This is especially important for virtual machines. +AD4 +AD4 commit b5b6e8c8d3b4 (+ACI-scsi: virtio+AF8-scsi: fix IO hang caused by automatic +AD4 irq vector affinity+ACI) made all virtio-scsi device to use blk-mq, which +AD4 does not contribute to randomness today. So for a virtual machine only +AD4 having virtio-scsi disk (which is common), it will simple stop getting +AD4 randomness from its disks in today's implementation. +AD4 +AD4 With this patch, if the above VM has rotational virtio-scsi device, then +AD4 it can still benefit from the entropy generated from the disk. +AD4 +AD4 Reported-by: Xuewei Zhang +ADw-xueweiz+AEA-google.com+AD4 +AD4 Signed-off-by: Xuewei Zhang +ADw-xueweiz+AEA-google.com+AD4 +AD4 --- +AD4 drivers/scsi/sd.c +AHw 3 +-+-+- +AD4 1 file changed, 3 insertions(+-) +AD4 +AD4 diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c +AD4 index b79b366a94f7..5e4f10d28065 100644 +AD4 --- a/drivers/scsi/sd.c +AD4 +-+-+- b/drivers/scsi/sd.c +AD4 +AEAAQA -2959,6 +-2959,9 +AEAAQA static void sd+AF8-read+AF8-block+AF8-characteristics(struct +AD4 scsi+AF8-disk +ACo-sdkp) +AD4 if (rot +AD0APQ 1) +AHs +AD4 blk+AF8-queue+AF8-flag+AF8-set(QUEUE+AF8-FLAG+AF8-NONROT, q)+ADs +AD4 blk+AF8-queue+AF8-flag+AF8-clear(QUEUE+AF8-FLAG+AF8-ADD+AF8-RANDOM, q)+ADs +AD4 +- +AH0 else +AHs +AD4 +- blk+AF8-queue+AF8-flag+AF8-clear(QUEUE+AF8-FLAG+AF8-NONROT, q)+ADs +AD4 +- blk+AF8-queue+AF8-flag+AF8-set(QUEUE+AF8-FLAG+AF8-ADD+AF8-RANDOM, q)+ADs +AD4 +AH0 +AD4 +AD4 if (sdkp-+AD4-device-+AD4-type +AD0APQ TYPE+AF8-ZBC) +AHs Although this patch looks fine to me, seeing this patch makes me wonder whether the default should be changed (QUEUE+AF8-FLAG+AF8-MQ+AF8-DEFAULT) instead of modifying the sd driver. Can anyone remind me why QUEUE+AF8-FLAG+AF8-MQ+AF8-DEFAULT does not include QUEUE+AF8-FLAG+AF8-ADD+AF8-RANDOM? Thanks, Bart.
