Re: [PATCH V4 04/24] xen/ioreq: Make x86's IOREQ feature common

[Julien Grall <julien@xxxxxxx>]

Hi Oleksandr,

On 12/01/2021 21:52, Oleksandr Tyshchenko wrote:
> From: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
>
> As a lot of x86 code can be re-used on Arm later on, this patch
> moves previously prepared IOREQ support to the common code
> (the code movement is verbatim copy).
>
> The "legacy" mechanism of mapping magic pages for the IOREQ servers
> remains x86 specific and not exposed to the common code.
>
> The common IOREQ feature is supposed to be built with IOREQ_SERVER
> option enabled, which is selected for x86's config HVM for now.
>
> In order to avoid having a gigantic patch here, the subsequent
> patches will update remaining bits in the common code step by step:
> - Make IOREQ related structs/materials common
> - Drop the "hvm" prefixes and infixes
> - Remove layering violation by moving corresponding fields
>    out of *arch.hvm* or abstracting away accesses to them
>
> Also include <xen/domain_page.h> which will be needed on Arm
> to avoid touch the common code again when introducing Arm specific bits.
>
> This support is going to be used on Arm to be able run device
> emulator outside of Xen hypervisor.
>
> Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
> CC: Julien Grall <julien.grall@xxxxxxx>
> [On Arm only]
> Tested-by: Wei Chen <Wei.Chen@xxxxxxx>
>
> ---
> Please note, this is a split/cleanup/hardening of Julien's PoC:
> "Add support for Guest IO forwarding to a device emulator"
>
> ***
> Please note, this patch depends on the following which is
> on review:
> https://patchwork.kernel.org/patch/11816689/
> ***
The effort was paused because we found a security issue around that code 
(see XSA-348). @Paul do you plan to revive it for 4.15?
Cheers,

--
Julien Grall