Re: [PATCH v8 2/5] xen/arm: Enable the existing x86 virtual PCI support for ARM

[Oleksandr Andrushchenko <Oleksandr_Andrushchenko@xxxxxxxx>]

On 18.10.21 13:29, Jan Beulich wrote:
> On 18.10.2021 12:11, Bertrand Marquis wrote:
>>> On 18 Oct 2021, at 08:47, Jan Beulich <jbeulich@xxxxxxxx> wrote:
>>> On 15.10.2021 18:51, Bertrand Marquis wrote:
>>>> --- /dev/null
>>>> +++ b/xen/arch/arm/vpci.c
>>>> @@ -0,0 +1,77 @@
>>>> +/*
>>>> + * xen/arch/arm/vpci.c
>>>> + *
>>>> + * This program is free software; you can redistribute it and/or modify
>>>> + * it under the terms of the GNU General Public License as published by
>>>> + * the Free Software Foundation; either version 2 of the License, or
>>>> + * (at your option) any later version.
>>>> + *
>>>> + * This program is distributed in the hope that 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.
>>>> + */
>>>> +#include <xen/sched.h>
>>>> +#include <xen/vpci.h>
>>>> +
>>>> +#include <asm/mmio.h>
>>>> +
>>>> +static int vpci_mmio_read(struct vcpu *v, mmio_info_t *info,
>>>> +                          register_t *r, void *p)
>>>> +{
>>>> +    pci_sbdf_t sbdf;
>>>> +    /* data is needed to prevent a pointer cast on 32bit */
>>>> +    unsigned long data;
>>>> +
>>>> +    /* We ignore segment part and always handle segment 0 */
>>>> +    sbdf.sbdf = VPCI_ECAM_BDF(info->gpa);
>>>> +
>>>> +    if ( vpci_ecam_read(sbdf, ECAM_REG_OFFSET(info->gpa),
>>>> +                        1U << info->dabt.size, &data) )
>>>> +    {
>>> Here it is quite clear that the SBDF you pass into vpci_ecam_read() is
>>> the virtual one. The function then calls vpci_read(), which in turn
>>> will call vpci_read_hw() in a number of situations (first and foremost
>>> whenever pci_get_pdev_by_domain() returns NULL). That function as well
>>> as pci_get_pdev_by_domain() use the passed in SBDF as if it was a
>>> physical one; I'm unable to spot any translation. Yet I do recall
>>> seeing assignment of a virtual device and function number somewhere
>>> (perhaps another of the related series), so the model also doesn't
>>> look to assume 1:1 mapping of SBDF.
>> This question was answered by Oleksandr I think.
> Yes; I continue to be sure though that I saw devfn allocation logic in
> one of the many patches that are related here. And I'm relatively sure
> that there no adjustment to logic here was made (but since it's hard
> to pick the right patch out of the huge pile without knowing its title,
> I can't reasonably go check).
Offtop: I was somehow dropped from the Cc..

Please see:

[PATCH v3 10/11] vpci: Add initial support for virtual PCI bus topology
[PATCH v3 11/11] xen/arm: Translate virtual PCI bus topology for guests

[1] https://patchwork.kernel.org/project/xen-devel/list/?series=555481