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

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

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.

Cheers
Bertrand

> 
> Thanks, Roger.