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I never >>> saw such implementation. >> I don't know of any real-world implementations like this, but the >> point of the spec is to allow interoperability without having to know >> about every implementation. > I did find at least one existing real-world driver implementation that > ignores blk_size and VIRTIO_BLK_F_BLK_SIZE - the u-boot virtio-blk > driver: https://github.com/u-boot/u-boot/blob/master/drivers/virtio/virtio_blk.c > > So this is not just spec language lawyering; this driver depends on > the ability to read/write at arbitrary 512-byte sector addresses and > data sizes, and it seems like it should be allowed to do that based on > my reading of the spec. > > (Perhaps u-boot's driver does not work with the QEMU's virtio-blk > device with certain storage configurations, per Stefan's note, but > that is again just one device implementation.) Vague specifications and inconsistent interpretations should be avoided. I'm trying to make the situation better. I'll send a V2 according to the comments. BTW, Are you familiar with some virtio-blk device that implements the buffer-cache logic you've described ? or is it only a theoretical discussion ? > > -- Daniel