On 21/10/2024 17:24, Luca Fancellu wrote:
Hi Ayan,
+ */
+FUNC_LOCAL(enable_mpu)
+ mrs x0, SCTLR_EL2
+ bic x0, x0, #SCTLR_ELx_BR /* Disable Background region */
+ orr x0, x0, #SCTLR_Axx_ELx_M /* Enable MPU */
+ orr x0, x0, #SCTLR_Axx_ELx_C /* Enable D-cache */
+ orr x0, x0, #SCTLR_Axx_ELx_WXN /* Enable WXN */
NIT: Can't we have a single "orr" instruction to set all the flags?
Yes, I will change this.
+ dsb sy
I still question this use of "dsb sy"...
Actually I kept this to ensure that all outstanding memory access are completed
before MPU is enabled.
However, prepare_xen_region() is invoked before this and it has a 'dsb sy' at
the end.
So we can drop this barrier.
I suggest to keep the barrier here and drop the one in prepare_xen_region
instead,
I think the barriers in prepare_xen_region() should be kept because we
may want to use the helper *after* the MPU is turned on.
have a look in my branch:
https://gitlab.com/xen-project/xen/-/merge_requests/7/diffs?commit_id=f42a2816f9bd95f2f6957887be910cb9acd140b5
During my testing I was having trouble without this barrier.
Was it before or after removing the barriers in prepare_xen_region()? If
the latter, then I am a bit puzzled why you need it. Did you investigate
a bit more?
Cheers,
--
Julien Grall
