RE: [virtio-comment] Comments on RPMB config space chapter 5.2.14

["Huang, Yang" <yang.huang@intel.com>]

> 1.) We have an underlying physical RPMB device we would like to forward to
> a virtual machine via virtio RPMB. Looks like the physical device has a
> capacity of 256. 256 > 0x80. And 256 also does not fit in the u8 capacity of the

256*128KB = 32MB RPMB. What's your flash, eMMC, UFS or NVMe?

> structure. Thinking now of cutting to 0x80 to fulfill the exact wording of the
> specification. Alternatively we might violate the specification and cut to 255
> which is the biggest value still fitting in u8 capacity. But nothing of this is
> satisfying.
> 
> 2.) Looking at the specification the maximum RPMB block count is 256. In our

What spec are you referring? Here is the description in eMMC Electrical Standard (5.1), JESD84-B51:
7.4.77 RPMB_SIZE_MULT [168]
The RPMB partition size is calculated from the register by using the following equation: RPMB partition
size = 128kB x RPMB_SIZE_MULT
Table 156 â RPMB Partition Size
Value Value definition
0x00 No RPMB partition available.
0x01 1 x 128Kbyte = 128Kbytes
0x02 2 x 128Kbyte = 256Kbytes
: :
0x80 128x128Kbyte = 16384Kbytes
0x81-0xFF Reserved1
NOTE 1 RPMB data frame format definition supports a maximum of 16 MB. This limits the size
of the RPMB area.