Re: [PATCH v5 1/3] xen/arm: mpu: Create boot-time MPU protection regions

[Julien Grall <julien@xxxxxxx>]

Hi Ayan,

On 07/11/2024 15:03, Ayan Kumar Halder wrote:
> +/*
> + * Macro to prepare and set a EL2 MPU memory region.
> + * We will also create an according MPU memory region entry, which
> + * is a structure of pr_t,  in table \prmap.
> + *
> + * Inputs:
> + * sel:         region selector
``sel`` is now also an output. But looking at the description, we don't 
seem to say which registers are preserved or not. For instance, both ..
> + * base:        reg storing base address (should be page-aligned) > + * limit: 
>       reg storing limit address
... the two registers above will be clobbered. On the other hand...

> + * prbar:       store computed PRBAR_EL2 value
> + * prlar:       store computed PRLAR_EL2 value
> + * maxcount:    maximum number of EL2 regions supported
... this will be preserved. So I think we need to clarify it. For 
instance, this is the description of create_table_entry_from_paddr:
/*
 * Macro to create a page table entry in \ptbl to \tbl
 * ptbl:    table symbol where the entry will be created
 * tbl:     physical address of the table to point to
 * virt:    virtual address
 * lvl:     page-table level
 * tmp1:    scratch register
 * tmp2:    scratch register
 *
 * Preserves \virt
 * Clobbers \tbl, \tmp1, \tmp2
 *
 * Note that all parameters using registers should be distinct.
 */

--
Julien Grall