Re: [PATCH V5 04/22] xen/ioreq: Make x86's IOREQ feature common

[Oleksandr <olekstysh@xxxxxxxxx>]

On 27.01.21 18:58, Jan Beulich wrote:

Hi Jan

> On 25.01.2021 20:08, 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
> >
> > Introduce asm/ioreq.h wrapper to be included by common ioreq.h
> > instead of asm/hvm/ioreq.h to avoid HVM-ism in the code common.
> >
> > 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>
> > Reviewed-by: Paul Durrant <paul@xxxxxxx>
> > CC: Julien Grall <julien.grall@xxxxxxx>
> > [On Arm only]
> > Tested-by: Wei Chen <Wei.Chen@xxxxxxx>
> Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
Thanks


> with ...
>
> > --- a/xen/arch/x86/Kconfig
> > +++ b/xen/arch/x86/Kconfig
> > @@ -92,6 +92,7 @@ config PV_LINEAR_PT
> >   
> >   config HVM
> >         def_bool !PV_SHIM_EXCLUSIVE
> > +       select IOREQ_SERVER
> >         prompt "HVM support"
> >         ---help---
> ... the addition moved below the prompt line (could probably
> be taken care of while committing, if no other need for a v6
> arises).
V6 is planned anyway, so will do, but ...


> (Personally I think this should be
>
> config HVM
>         bool "HVM support"
>         default !PV_SHIM_EXCLUSIVE
... def_bool is changed to default by intention or this is a typo?


>         select IOREQ_SERVER
>         ---help---
>
> anyway, but that's nothing you need to care about.)
>
> > --- /dev/null
> > +++ b/xen/include/asm-x86/ioreq.h
> > @@ -0,0 +1,37 @@
> > +/*
> > + * ioreq.h: Hardware virtual machine assist interface definitions.
> > + *
> > + * This is a wrapper which purpose is to not include arch HVM specific header
> > + * from the common code.
> > + *
> > + * Copyright (c) 2016 Citrix Systems Inc.
> > + *
> > + * This program is free software; you can redistribute it and/or modify it
> > + * under the terms and conditions of the GNU General Public License,
> > + * version 2, as published by the Free Software Foundation.
> > + *
> > + * This program is distributed in the hope it will be useful, but WITHOUT
> > + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> > + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
> > + * more details.
> > + *
> > + * You should have received a copy of the GNU General Public License along with
> > + * this program; If not, see <http://www.gnu.org/licenses/>.
> > + */
> > +
> > +#ifndef __ASM_X86_IOREQ_H__
> > +#define __ASM_X86_IOREQ_H__
> > +
> > +#include <asm/hvm/ioreq.h>
> > +
> > +#endif /* __ASM_X86_IOREQ_H__ */
> Not necessarily for taking care of right away, I think in the
> longer run this wants wrapping by #ifdef CONFIG_HVM, such that
> in !HVM builds the dependency on the "chained" header goes
> away (reducing the amount of rebuilding in incremental builds).
I don't mind wrapping it right away.


> Jan
--
Regards,

Oleksandr Tyshchenko