Re: [PATCH v2 1/2] xen/mpu: Map early uart when earlyprintk on

[Julien Grall <julien@xxxxxxx>]

On 03/12/2024 13:34, Ayan Kumar Halder wrote:
> On 02/12/2024 20:53, Julien Grall wrote:
> > Hi Ayan,
> Hi Julien,
> > On 27/11/2024 18:39, Ayan Kumar Halder wrote:
> > > CONFIG_EARLY_UART_SIZE is introduced to let user provide physical 
> > > size of
> > > early UART. Unlike MMU where we map a page in the virtual address space,
> > > here we need to know the exact physical size to be mapped.
> > > As VA == PA in case of MPU, the memory layout follows exactly the 
> > > hardware
> > > configuration. As a consequence, we set EARLY_UART_VIRTUAL_ADDRESS as 
> > > physical
> > > address.
> > >
> > > EARLY_UART_BASE_ADDRESS and EARLY_UART_SIZE should be aligned to the 
> > > minimum
> > > size of MPU region (ie 64 bits) as per the hardware restrictions. 
> > > Refer ARM
> > > DDI 0600A.d ID120821 A1.3 "A minimum protection region size of 64 
> > > bytes.".
> > > UART is mapped as nGnRE region (as specified by ATTR=100 , refer 
> > > G1.3.13,
> > > MAIR_EL2, "---0100 Device memory nGnRE") and Doc ID - 102670_0101_02_en
> > I can't find the Doc you point online. Do you have a link?
> https://developer.arm.com/documentation/102670/0101 - Cortex-R82 
> processor TRM
Thanks. But why are you quoting the Cortex-R82 TRM? This code is meant 
to work on any Armv8-R processor.
Cheers,

--
Julien Grall