Re: [PATCH V2 01/23] x86/ioreq: Prepare IOREQ feature for making it common

From: Oleksandr <olekstysh@gmail.com>
To: Jan Beulich <jbeulich@suse.com>
Cc: "Oleksandr Tyshchenko" <oleksandr_tyshchenko@epam.com>,
	"Paul Durrant" <paul@xen.org>,
	"Andrew Cooper" <andrew.cooper3@citrix.com>,
	"Roger Pau Monné" <roger.pau@citrix.com>,
	"Julien Grall" <julien@xen.org>,
	"Stefano Stabellini" <sstabellini@kernel.org>,
	"Wei Liu" <wl@xen.org>, "Julien Grall" <julien.grall@arm.com>,
	xen-devel@lists.xenproject.org
Subject: Re: [PATCH V2 01/23] x86/ioreq: Prepare IOREQ feature for making it common
Date: Fri, 13 Nov 2020 13:09:37 +0200	[thread overview]
Message-ID: <cd16e1f2-849d-ec12-3325-382b8f6689ff@gmail.com> (raw)
In-Reply-To: <61ea02e0-bdd4-5a0a-dd6f-b22e806e6d1e@suse.com>

On 12.11.20 12:58, Jan Beulich wrote:

Hi Jan.

> On 15.10.2020 18:44, Oleksandr Tyshchenko wrote:
>> From: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
>>
>> As a lot of x86 code can be re-used on Arm later on, this
>> patch makes some preparation to x86/hvm/ioreq.c before moving
>> to the common code. This way we will get a verbatim copy for
>> a code movement in subsequent patch (arch/x86/hvm/ioreq.c
>> will be *just* renamed to common/ioreq).
>>
>> This patch does the following:
>> 1. Introduce *inline* arch_hvm_ioreq_init(), arch_hvm_ioreq_destroy(),
>>     arch_hvm_io_completion(), arch_hvm_destroy_ioreq_server() and
>>     hvm_ioreq_server_get_type_addr() to abstract arch specific materials.
>> 2  Make hvm_map_mem_type_to_ioreq_server() *inline*. It is not going
>>     to be called from the common code.
> As already indicated on another sub-thread, I think some of these
> are too large to be inline functions. Additionally, considering
> their single-use purpose, I don't think they should be placed in
> a header consumed by more than the producer and the sole consumer.
ok, the only reason I made these inline was to achieve a moving of the 
whole x86/hvm/ioreq.c to the common code.
I will move some of them back to ioreq.c.

>
>> 3. Make get_ioreq_server() global. It is going to be called from
>>     a few places.
> And with this its name ought to change, to fit the general naming
> model of global functions of this subsystem.
I think, with new requirements (making 
hvm_map_mem_type_to_ioreq_server() common) this helper
doesn't need to be global. I will make it static again.

>
>> 4. Add IOREQ_STATUS_* #define-s and update candidates for moving.
> This, it seems to me, could be a separate patch.

Well, will do.

>
>> @@ -855,7 +841,7 @@ int hvm_destroy_ioreq_server(struct domain *d, ioservid_t id)
>>   
>>       domain_pause(d);
>>   
>> -    p2m_set_ioreq_server(d, 0, s);
>> +    arch_hvm_destroy_ioreq_server(s);
> Iirc there are plans to rename hvm_destroy_ioreq_server() in the
> course of the generalization. If so, this arch hook would imo
> better be named following the new scheme right away.
Could you please clarify, are you speaking about the plans discussed there

"[PATCH V2 12/23] xen/ioreq: Remove "hvm" prefixes from involved 
function names"?

Copy text for the convenience:
AT least some of the functions touched here would be nice to be
moved to a more consistent new naming scheme right away, to
avoid having to touch all the same places again. I guess ioreq
server functions would be nice to all start with ioreq_server_
and ioreq functions to all start with ioreq_. E.g. ioreq_send()
and ioreq_server_select().

or some other plans I am not aware of?

What I really want to avoid with IOREQ enabling work is the round-trips 
related to naming things, this patch series
became quite big (and consumes som time to rebase and test it) and I 
expect it to become bigger.

So the arch_hvm_destroy_ioreq_server() should be 
arch_ioreq_server_destroy()?

>
>> @@ -1215,7 +1153,7 @@ void hvm_destroy_all_ioreq_servers(struct domain *d)
>>       struct hvm_ioreq_server *s;
>>       unsigned int id;
>>   
>> -    if ( !relocate_portio_handler(d, 0xcf8, 0xcf8, 4) )
>> +    if ( !arch_hvm_ioreq_destroy(d) )
> There's no ioreq being destroyed here, so I think this wants
> renaming (and again ideally right away following the planned
> new scheme).
Agree that no ioreq being destroyed here. Probably 
ioreq_server_check_for_destroy()?
I couldn't think of a better name.

>
>> +static inline int hvm_map_mem_type_to_ioreq_server(struct domain *d,
>> +                                                   ioservid_t id,
>> +                                                   uint32_t type,
>> +                                                   uint32_t flags)
>> +{
>> +    struct hvm_ioreq_server *s;
>> +    int rc;
>> +
>> +    if ( type != HVMMEM_ioreq_server )
>> +        return -EINVAL;
>> +
>> +    if ( flags & ~XEN_DMOP_IOREQ_MEM_ACCESS_WRITE )
>> +        return -EINVAL;
>> +
>> +    spin_lock_recursive(&d->arch.hvm.ioreq_server.lock);
>> +
>> +    s = get_ioreq_server(d, id);
>> +
>> +    rc = -ENOENT;
>> +    if ( !s )
>> +        goto out;
>> +
>> +    rc = -EPERM;
>> +    if ( s->emulator != current->domain )
>> +        goto out;
>> +
>> +    rc = p2m_set_ioreq_server(d, flags, s);
>> +
>> + out:
>> +    spin_unlock_recursive(&d->arch.hvm.ioreq_server.lock);
>> +
>> +    if ( rc == 0 && flags == 0 )
>> +    {
>> +        struct p2m_domain *p2m = p2m_get_hostp2m(d);
> I realize I may be asking too much, but would it be possible if,
> while moving code, you made simple and likely uncontroversial
> adjustments like adding const here? (Such adjustments would be
> less desirable to make if they increased the size of the patch,
> e.g. if you were touching only nearby code.)
This function as well as one located below won't be moved to this header
for the next version of patch.

ok, will add const.

>
>> +        if ( read_atomic(&p2m->ioreq.entry_count) )
>> +            p2m_change_entry_type_global(d, p2m_ioreq_server, p2m_ram_rw);
>> +    }
>> +
>> +    return rc;
>> +}
>> +
>> +static inline int hvm_ioreq_server_get_type_addr(const struct domain *d,
>> +                                                 const ioreq_t *p,
>> +                                                 uint8_t *type,
>> +                                                 uint64_t *addr)
>> +{
>> +    uint32_t cf8 = d->arch.hvm.pci_cf8;
> Similarly, for example, neither this nor ...
>
>> +    if ( p->type != IOREQ_TYPE_COPY && p->type != IOREQ_TYPE_PIO )
>> +        return -EINVAL;
>> +
>> +    if ( p->type == IOREQ_TYPE_PIO &&
>> +         (p->addr & ~3) == 0xcfc &&
>> +         CF8_ENABLED(cf8) )
>> +    {
>> +        uint32_t x86_fam;
> ... this really need to use a fixed width type - unsigned int is
> going to be quite fine. But since you're only moving this code,
> I guess I'm not going to insist.

Will use unsigned int.

>
>> +static inline bool arch_hvm_ioreq_destroy(struct domain *d)
>> +{
>> +    if ( !relocate_portio_handler(d, 0xcf8, 0xcf8, 4) )
>> +        return false;
>> +
>> +    return true;
> Any reason this cannot simply be
>
>      return relocate_portio_handler(d, 0xcf8, 0xcf8, 4);

Yes, good point.

-- 
Regards,

Oleksandr Tyshchenko