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

[Oleksandr Andrushchenko <Oleksandr_Andrushchenko@epam.com>]

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]

Thank you,
Oleksandr

[1] https://patchwork.kernel.org/project/xen-devel/patch/20211008055535.337436-9-andr2000@gmail.com/