Re: [Xen-devel] [PATCH v6 07/24] arm/x86/vmap: Add vmalloc_type and vm_init_type

[Julien Grall <julien.grall@xxxxxxx>]

Hi Konrad,

On 07/04/16 04:49, Konrad Rzeszutek Wilk wrote:
> For those users who want to use the virtual addresses that
> are in the hypervisor's virtual address space - these two new
> functions allow that. Along with providing the underlaying
> MFNs for the user's (such as changing page table permissions).
>
> Implementation wise the vmap API keeps track of two virtual
> address regions now:
>   a) VMAP_VIRT_START
>   b) Any provided virtual address space (need start and end).
>
> The a) one is the default one and the existing behavior
> for users of vmalloc, vmap, etc is the same.
>
> If however one wishes to use the b) one only has to use
> the vm_init_type to initalize and the vmalloc_type to utilize it.
NIT: s/initalize/initialize/

> This allows users (such as xSplice) to provide their own
> mechanism to change the the page flags, and also use virtual
> addresses closer to the hypervisor virtual addresses (at least
> on x86) while not having to deal with the allocation of
> pages.
>
> For example of users, see patch titled "xsplice: Implement payload
> loading", where we parse the payload's ELF relocations - which
> is defined to be signed 32-bit (so max displacement is 2GB virtual
> spacE). The displacement of the hypervisor virtual addresses to the
> vmalloc (on x86) is more than 32-bits - which means that ELF relocations
> would truncate the 34 and 33th bit. Hence this alternate API
NIT: Missing full stop.

> We also add add extra checks in case the b) range has not been initialized.
>
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> Suggested-by: Jan Beulich <jbeulich@xxxxxxxx>
For the ARM parts:

Acked-by: Julien Grall <julien.grall@xxxxxxx>

Regards,

--
Julien Grall

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