Re: [PATCH V4 14/24] arm/ioreq: Introduce arch specific bits for IOREQ/DM features

[Julien Grall <julien@xxxxxxx>]

On 17/01/2021 17:11, Oleksandr wrote:
> On 15.01.21 22:26, Julien Grall wrote:
>
> Hi Julien
Hi Oleksandr,

> > > +
> > >       PROGRESS(xen):
> > >           ret = relinquish_memory(d, &d->xenpage_list);
> > >           if ( ret )
> > > diff --git a/xen/arch/arm/io.c b/xen/arch/arm/io.c
> > > index ae7ef96..9814481 100644
> > > --- a/xen/arch/arm/io.c
> > > +++ b/xen/arch/arm/io.c
> > > @@ -16,6 +16,7 @@
> > >    * GNU General Public License for more details.
> > >    */
> > >   +#include <xen/ioreq.h>
> > >   #include <xen/lib.h>
> > >   #include <xen/spinlock.h>
> > >   #include <xen/sched.h>
> > > @@ -23,6 +24,7 @@
> > >   #include <asm/cpuerrata.h>
> > >   #include <asm/current.h>
> > >   #include <asm/mmio.h>
> > > +#include <asm/hvm/ioreq.h>
> > Shouldn't this have been included by "xen/ioreq.h"?
> Well, for V1 asm/hvm/ioreq.h was included by xen/ioreq.h. But, it turned 
> out that there was nothing inside common header required arch one to be 
> included and
> I was asked to include arch header where it was indeed needed (several 
> *.c files).
Fair enough.

[...]

> > If you return IO_HANDLED here, then it means the we will take care of 
> > previous I/O but the current one is going to be ignored. 
> Which current one? As I understand, if try_fwd_ioserv() gets called with 
> vio->req.state == STATE_IORESP_READY then this is a second round after 
> emulator completes the emulation (the first round was when
> we returned IO_RETRY down the function and claimed that we would need a 
> completion), so we are still dealing with previous I/O.
> vcpu_ioreq_handle_completion() -> arch_ioreq_complete_mmio() -> 
> try_handle_mmio() -> try_fwd_ioserv() -> handle_ioserv()
> And after we return IO_HANDLED here, handle_ioserv() will be called to 
> complete the handling of this previous I/O emulation.
> Or I really missed something?
Hmmm... I somehow thought try_fw_ioserv() would only be called the first 
time. Do you have a branch with your code applied? This would help to 
follow the different paths.
> > >   diff --git a/xen/include/asm-arm/domain.h 
> > > b/xen/include/asm-arm/domain.h
> > > index 6819a3b..c235e5b 100644
> > > --- a/xen/include/asm-arm/domain.h
> > > +++ b/xen/include/asm-arm/domain.h
> > > @@ -10,6 +10,7 @@
> > >   #include <asm/gic.h>
> > >   #include <asm/vgic.h>
> > >   #include <asm/vpl011.h>
> > > +#include <public/hvm/dm_op.h>
> > May I ask, why do you need to include dm_op.h here?
> I needed to include that header to make some bits visible 
> (XEN_DMOP_IO_RANGE_PCI, struct xen_dm_op_buf, etc). Why here - is a 
> really good question.
> I don't remember exactly, probably I followed x86's domain.h which also 
> included it.
> So, trying to remove the inclusion here, I get several build failures on 
> Arm which could be fixed if I include that header from dm.h and ioreq.h:
> Shall I do this way?
If the failure are indeded because ioreq.h and dm.h use definition from 
public/hvm/dm_op.h, then yes. Can you post the errors?
[...]

> > >   #include <public/hvm/params.h>
> > >     struct hvm_domain
> > > @@ -262,6 +263,8 @@ static inline void arch_vcpu_block(struct vcpu 
> > > *v) {}
> > >     #define arch_vm_assist_valid_mask(d) (1UL << 
> > > VMASST_TYPE_runstate_update_flag)
> > >   +#define has_vpci(d)    ({ (void)(d); false; })
> > > +
> > >   #endif /* __ASM_DOMAIN_H__ */
> > >     /*
> > > diff --git a/xen/include/asm-arm/hvm/ioreq.h 
> > > b/xen/include/asm-arm/hvm/ioreq.h
> > > new file mode 100644
> > > index 0000000..19e1247
> > > --- /dev/null
> > > +++ b/xen/include/asm-arm/hvm/ioreq.h
> > Shouldn't this directly be under asm-arm/ rather than asm-arm/hvm/ as 
> > the IOREQ is now meant to be agnostic?
> Good question... The _common_ IOREQ code is indeed arch-agnostic. But, 
> can the _arch_ IOREQ code be treated as really subarch-agnostic?
> I think, on Arm it can and it is most likely ok to keep it in 
> "asm-arm/", but how it would be correlated with x86's IOREQ code which 
> is HVM specific and located
> in "hvm" subdir?
Sorry, I don't understand your answer/questions. So let me ask the 
question differently, is asm-arm/hvm/ioreq.h going to be included from 
common code?
If the answer is no, then I see no reason to follow the x86 here.
If the answer is yes, then I am quite confused why half of the series 
tried to remove "hvm" from the function name but we still include 
"asm/hvm/ioreq.h".
Cheers,

--
Julien Grall