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

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

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@xxxxxxxxxx> 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@xxxxxxx>
> >>> Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
> >>> ---
> >>> Change in v5:
> >>> - Add pci_cleanup_msi(pdev) in cleanup part.
> >>> - Added Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
> >>> 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.

Thanks, Roger.