MPU

Number of regions: 0, 1, 2, 4, 8, 16
There is always 1 default region that does not contribute to the number of regions. If the address being handled does not fit into any of the regions, then this default region is used. This means that you can have 0 regions and still have MPU enabled. In this case, only the default region will be considered.
Region size: 32 bytes, 64 bytes, ..., 64 KB, 256 KB, ..., 2 GB, 4 GB
Each region's effective address is as such that its start address is a multiple of its size. e.g. If you define the size of a region to be 32 bytes and its address 50, it is not going to cover address 50 till 82. Instead, the region will be spanned over address 32 till 64.
Possible permissions: kernel read/write/execute; user read/write/execute
User access implies kernel access. e.g. if user is allowed to read a memory region, then the kernel can too, irrespective of if kernel read permission is set or not.
Regions with lower index have higher priority. For instance, in case of overlap between the regions addresses, the permission of a lower region is considered (region0 >> region 1 >> ... >> region15).

In the table below, you find the parameters that ARC-QEMU provides for configuring MPU:

Parameter	Default	Value	Description
-global cpu.mpu-numreg	0	0, 1, 2, 4, 8, 16	number of regions available
-global cpu.has-mpu	true	false, true	MPU subsystem availability

reg name	gdb name	comment
`mpu_build`	`$mpu_build`	version filed is hardcoded to 3
`mpuen`	`$mpuen`
`mpuic`	`$mpuecr`	this is addressed as `MPU_ECR` in reference manual
`mpurdb0`	`$mpurdb0`	at least number of regions must be configured to 1
`mpurdp0`	`$mpurdp0`	"
`mpurdb1`	`$mpurdb1`	at least number of regions must be configured to 2
`mpurdp1`	`$mpurdp1`	"
`mpurdb2`	`$mpurdb2`	at least number of regions must be configured to 4
`mpurdp2`	`$mpurdp2`	"
`mpurdb3`	`$mpurdb3`	"
`mpurdp3`	`$mpurdp3`	"
`mpurdb4`	`$mpurdb4`	at least number of regions must be configured to 8
`mpurdp4`	`$mpurdp4`	"
`mpurdb5`	`$mpurdb5`	"
`mpurdp5`	`$mpurdp5`	"
`mpurdb6`	`$mpurdb6`	"
`mpurdp6`	`$mpurdp6`	"
`mpurdb7`	`$mpurdb7`	"
`mpurdp7`	`$mpurdp7`	"
`mpurdb8`	`$mpurdb8`	number of regions must be configured to 16
`mpurdp8`	`$mpurdp8`	"
`mpurdb9`	`$mpurdb9`	"
`mpurdp9`	`$mpurdp9`	"
`mpurdb10`	`$mpurdb10`	"
`mpurdp10`	`$mpurdp10`	"
`mpurdb11`	`$mpurdb11`	"
`mpurdp11`	`$mpurdp11`	"
`mpurdb12`	`$mpurdb12`	"
`mpurdp12`	`$mpurdp12`	"
`mpurdb13`	`$mpurdb13`	"
`mpurdp13`	`$mpurdp13`	"
`mpurdb14`	`$mpurdb14`	"
`mpurdp14`	`$mpurdp14`	"
`mpurdb15`	`$mpurdb15`	"
`mpurdp15`	`$mpurdp15`	"

You may get information about MPU by passing -d mmu to qemu-system-arc. For better details, please consult the troubleshooting page.

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