Re: [PATCH v5 08/11] xen/arm: Enable the existing x86 virtual PCI support for ARM.

[Bertrand Marquis <Bertrand.Marquis@arm.com>]

Hi Stefano,

> On 11 Oct 2021, at 20:27, Stefano Stabellini <sstabellini@kernel.org> wrote:
> 
> On Mon, 11 Oct 2021, Oleksandr Andrushchenko wrote:
>> On 11.10.21 20:15, Bertrand Marquis wrote:
>>> Hi Roger,
>>> 
>>>> On 11 Oct 2021, at 17:43, Roger Pau Monné <roger.pau@citrix.com> wrote:
>>>> 
>>>> On Mon, Oct 11, 2021 at 04:20:14PM +0000, Oleksandr Andrushchenko wrote:
>>>>> 
>>>>> On 11.10.21 19:12, Bertrand Marquis wrote:
>>>>>> Hi Roger,
>>>>>> 
>>>>>>> On 11 Oct 2021, at 11:51, Roger Pau Monné <roger.pau@citrix.com> wrote:
>>>>>>> 
>>>>>>> On Wed, Oct 06, 2021 at 06:40:34PM +0100, Rahul Singh wrote:
>>>>>>>> The existing VPCI support available for X86 is adapted for Arm.
>>>>>>>> When the device is added to XEN via the hyper call
>>>>>>>> “PHYSDEVOP_pci_device_add”, VPCI handler for the config space
>>>>>>>> access is added to the Xen to emulate the PCI devices config space.
>>>>>>>> 
>>>>>>>> A MMIO trap handler for the PCI ECAM space is registered in XEN
>>>>>>>> so that when guest is trying to access the PCI config space,XEN
>>>>>>>> will trap the access and emulate read/write using the VPCI and
>>>>>>>> not the real PCI hardware.
>>>>>>>> 
>>>>>>>> For Dom0less systems scan_pci_devices() would be used to discover the
>>>>>>>> PCI device in XEN and VPCI handler will be added during XEN boots.
>>>>>>>> 
>>>>>>>> Signed-off-by: Rahul Singh <rahul.singh@arm.com>
>>>>>>>> Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
>>>>>>>> ---
>>>>>>>> Change in v5:
>>>>>>>> - Add pci_cleanup_msi(pdev) in cleanup part.
>>>>>>>> - Added Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
>>>>>>>> Change in v4:
>>>>>>>> - Move addition of XEN_DOMCTL_CDF_vpci flag to separate patch
>>>>>>>> Change in v3:
>>>>>>>> - Use is_pci_passthrough_enabled() in place of pci_passthrough_enabled variable
>>>>>>>> - Reject XEN_DOMCTL_CDF_vpci for x86 in arch_sanitise_domain_config()
>>>>>>>> - Remove IS_ENABLED(CONFIG_HAS_VPCI) from has_vpci()
>>>>>>>> Change in v2:
>>>>>>>> - Add new XEN_DOMCTL_CDF_vpci flag
>>>>>>>> - modify has_vpci() to include XEN_DOMCTL_CDF_vpci
>>>>>>>> - enable vpci support when pci-passthough option is enabled.
>>>>>>>> ---
>>>>>>>> ---
>>>>>>>> xen/arch/arm/Makefile         |   1 +
>>>>>>>> xen/arch/arm/domain.c         |   4 ++
>>>>>>>> xen/arch/arm/domain_build.c   |   3 +
>>>>>>>> xen/arch/arm/vpci.c           | 102 ++++++++++++++++++++++++++++++++++
>>>>>>>> xen/arch/arm/vpci.h           |  36 ++++++++++++
>>>>>>>> xen/drivers/passthrough/pci.c |  18 ++++++
>>>>>>>> xen/include/asm-arm/domain.h  |   7 ++-
>>>>>>>> xen/include/asm-x86/pci.h     |   2 -
>>>>>>>> xen/include/public/arch-arm.h |   7 +++
>>>>>>>> xen/include/xen/pci.h         |   2 +
>>>>>>>> 10 files changed, 179 insertions(+), 3 deletions(-)
>>>>>>>> create mode 100644 xen/arch/arm/vpci.c
>>>>>>>> create mode 100644 xen/arch/arm/vpci.h
>>>>>>>> 
>>>>>>>> diff --git a/xen/arch/arm/Makefile b/xen/arch/arm/Makefile
>>>>>>>> index 44d7cc81fa..fb9c976ea2 100644
>>>>>>>> --- a/xen/arch/arm/Makefile
>>>>>>>> +++ b/xen/arch/arm/Makefile
>>>>>>>> @@ -7,6 +7,7 @@ ifneq ($(CONFIG_NO_PLAT),y)
>>>>>>>> obj-y += platforms/
>>>>>>>> endif
>>>>>>>> obj-$(CONFIG_TEE) += tee/
>>>>>>>> +obj-$(CONFIG_HAS_VPCI) += vpci.o
>>>>>>>> 
>>>>>>>> obj-$(CONFIG_HAS_ALTERNATIVE) += alternative.o
>>>>>>>> obj-y += bootfdt.init.o
>>>>>>>> diff --git a/xen/arch/arm/domain.c b/xen/arch/arm/domain.c
>>>>>>>> index 36138c1b2e..fbb52f78f1 100644
>>>>>>>> --- a/xen/arch/arm/domain.c
>>>>>>>> +++ b/xen/arch/arm/domain.c
>>>>>>>> @@ -39,6 +39,7 @@
>>>>>>>> #include <asm/vgic.h>
>>>>>>>> #include <asm/vtimer.h>
>>>>>>>> 
>>>>>>>> +#include "vpci.h"
>>>>>>>> #include "vuart.h"
>>>>>>>> 
>>>>>>>> DEFINE_PER_CPU(struct vcpu *, curr_vcpu);
>>>>>>>> @@ -767,6 +768,9 @@ int arch_domain_create(struct domain *d,
>>>>>>>>     if ( is_hardware_domain(d) && (rc = domain_vuart_init(d)) )
>>>>>>>>         goto fail;
>>>>>>>> 
>>>>>>>> +    if ( (rc = domain_vpci_init(d)) != 0 )
>>>>>>>> +        goto fail;
>>>>>>>> +
>>>>>>>>     return 0;
>>>>>>>> 
>>>>>>>> fail:
>>>>>>>> diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
>>>>>>>> index c5afbe2e05..f4c89bde8c 100644
>>>>>>>> --- a/xen/arch/arm/domain_build.c
>>>>>>>> +++ b/xen/arch/arm/domain_build.c
>>>>>>>> @@ -3053,6 +3053,9 @@ void __init create_dom0(void)
>>>>>>>>     if ( iommu_enabled )
>>>>>>>>         dom0_cfg.flags |= XEN_DOMCTL_CDF_iommu;
>>>>>>>> 
>>>>>>>> +    if ( is_pci_passthrough_enabled() )
>>>>>>>> +        dom0_cfg.flags |= XEN_DOMCTL_CDF_vpci;
>>>>>>> I think I'm confused with this. You seem to enable vPCI for dom0, but
>>>>>>> then domain_vpci_init will setup traps for the guest virtual ECAM
>>>>>>> layout, not the native one that dom0 will be using.
>>>>>> I think after the last discussions, it was decided to also installed the vpci
>>>>>> handler for dom0. I will have to look into this and come back to you.
>>>>>> @Oleksandr: Could you comment on this.
>>>>> Yes, we do trap Dom0 as well. The Dom0 traps are not in this series, but
>>>>> are in mine as it needs more preparatory work for that. Please see [1]
>>>> Then I don't think we should set XEN_DOMCTL_CDF_vpci for dom0 here, it
>>>> should instead be done in the patch where dom0 support is introduced.
>>> Ok I will check to remove this and include the change in v6.
>> Just to make it clear: do we want to remove this piece from this patch
>> and instead have a dedicated patch on top of my series, so it is enabled
>> right after we have the code that sets up the trap handlers for Dom0?
>> If so, then do we want that patch to be chained in my series or sent as
>> a follow up right after it separately?
> 
> I think we want to remove the XEN_DOMCTL_CDF_vpci chunk from this patch.
> 
> Where exactly it should be introduced, I am not sure. I think it would
> be OK as a separate single patch at the end. I doesn't have to be part
> of the outstanding series, considering that we are also missing the
> patch to add "select HAS_PCI" for ARM.

Agree, I will remove that from v6.

Cheers
Bertrand