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

[Bertrand Marquis <Bertrand.Marquis@xxxxxxx>]

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.

> 
>> +
>>     dom0 = domain_create(0, &dom0_cfg, true);
>>     if ( IS_ERR(dom0) || (alloc_dom0_vcpu0(dom0) == NULL) )
>>         panic("Error creating domain 0\n");
>> diff --git a/xen/arch/arm/vpci.c b/xen/arch/arm/vpci.c
>> new file mode 100644
>> index 0000000000..76c12b9281
>> --- /dev/null
>> +++ b/xen/arch/arm/vpci.c
>> @@ -0,0 +1,102 @@
>> +/*
>> + * 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 <asm/mmio.h>
>> +
>> +#define REGISTER_OFFSET(addr)  ( (addr) & 0x00000fff)
>> +
>> +/* Do some sanity checks. */
>> +static bool vpci_mmio_access_allowed(unsigned int reg, unsigned int len)
>> +{
>> +    /* Check access size. */
>> +    if ( len > 8 )
>> +        return false;
>> +
>> +    /* Check that access is size aligned. */
>> +    if ( (reg & (len - 1)) )
>> +        return false;
>> +
>> +    return true;
>> +}
> 
> There's a vpci_access_allowed which I think you could generalize and
> use here, there's no need to have this duplicated code.

It definitely looks exactly like what we want to do.

I would need to turn this into a static inline and put it in some global header.
It is currently in arch/x86/hvm/io.c, any suggestion on the header to move it 
to ?

Regards
Bertrand

> 
> Thanks, Roger.