Re: [PATCH v6 2/3] xen/arm: Enable the existing x86 virtual PCI support for ARM.

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

On Thu, Oct 14, 2021 at 03:49:50PM +0100, Bertrand Marquis wrote:
> From: Rahul Singh <rahul.singh@xxxxxxx>
> 
> 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.
> 
> This patch is also doing some small fixes to fix compilation errors on
> arm32 of vpci:
> - add a cast to unsigned long in print in header.c
> - add a cast to uint64_t in vpci_ecam_mmio_write
> 
> Signed-off-by: Rahul Singh <rahul.singh@xxxxxxx>
> Signed-off-by: Bertrand Marquis <bertrand.marquis@xxxxxxx>
> ---
> Changes in v6:
> - Use new vpci_ecam_ helpers for PCI access
> - Do not set XEN_DOMCTL_CDF_vpci for dom0 for now (will be done in a
> future patch once everything is ready)

Isn't the series missing a revert of XEN_DOMCTL_CDF_vpci? I think
that's what we agreed would be the way forward.

> - rename REGISTER_OFFSET to ECAM_REG_OFFSET and move it to pci.h
> - remove not needed local variables in vpci_mmio_write, the one in read
> has been kept to ensure proper compilation on arm32
> - move call to vpci_add_handlers before iommu init to simplify exit path
> - move call to pci_cleanup_msi in the out section of pci_add_device if
> pdev is not NULL and on error
> - initialize pdev to NULL to handle properly exit path call of
> pci_cleanup_msi
> - keep has_vpci to return false for now as CFG_vpci has been removed.
> Added a comment on top of the definition.
> - fix compilation errors on arm32 (print in header.c, cast missing in
> mmio_write.
> - local variable was kept in vpci_mmio_read on arm to prevent a cast
> error in arm32.
> Change in v5:
> - Add pci_cleanup_msi(pdev) incleanup 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/vpci.c           | 74 +++++++++++++++++++++++++++++++++++
>  xen/arch/arm/vpci.h           | 36 +++++++++++++++++
>  xen/drivers/passthrough/pci.c | 18 ++++++++-
>  xen/drivers/vpci/header.c     |  3 +-
>  xen/drivers/vpci/vpci.c       |  2 +-
>  xen/include/asm-arm/domain.h  |  1 +
>  xen/include/asm-x86/pci.h     |  2 -
>  xen/include/public/arch-arm.h |  7 ++++
>  xen/include/xen/pci.h         |  3 ++
>  11 files changed, 146 insertions(+), 5 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 64518848b2..07f634508e 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 eef0661beb..96e1b23550 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);
> @@ -773,6 +774,9 @@ 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/vpci.c b/xen/arch/arm/vpci.c
> new file mode 100644
> index 0000000000..7c3552b65d
> --- /dev/null
> +++ b/xen/arch/arm/vpci.c
> @@ -0,0 +1,74 @@
> +/*
> + * 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 <xen/vpci.h>
> +
> +#include <asm/mmio.h>
> +
> +static int vpci_mmio_read(struct vcpu *v, mmio_info_t *info,
> +                          register_t *r, void *p)
> +{
> +    pci_sbdf_t sbdf;
> +    /* data is needed to prevent a pointer cast on 32bit */
> +    unsigned long data = ~0ul;
> +    int ret;
> +
> +    /* We ignore segment part and always handle segment 0 */
> +    sbdf.sbdf = ECAM_BDF(info->gpa);
> +
> +    ret = vpci_ecam_mmio_read(sbdf, ECAM_REG_OFFSET(info->gpa),
> +                              1U << info->dabt.size, &data);
> +
> +    *r = data;
> +
> +    return ret;
> +}
> +
> +static int vpci_mmio_write(struct vcpu *v, mmio_info_t *info,
> +                           register_t r, void *p)
> +{
> +    pci_sbdf_t sbdf;
> +
> +    /* We ignore segment part and always handle segment 0 */
> +    sbdf.sbdf = ECAM_BDF(info->gpa);
> +
> +    return vpci_ecam_mmio_write(sbdf, ECAM_REG_OFFSET(info->gpa),
> +                                1U << info->dabt.size, r);
> +}

I'm not sure returning an error value here is helpful, as I'm not sure
how native Arm behaves and how this error is propagated into the
guest. FWIWreturning ~0 or dropping writes is what we do in x86 when
vPCI is not capable of handling the access.

> +
> +static const struct mmio_handler_ops vpci_mmio_handler = {
> +    .read  = vpci_mmio_read,
> +    .write = vpci_mmio_write,
> +};
> +
> +int domain_vpci_init(struct domain *d)
> +{
> +    if ( !has_vpci(d) )
> +        return 0;
> +
> +    register_mmio_handler(d, &vpci_mmio_handler,
> +                          GUEST_VPCI_ECAM_BASE, GUEST_VPCI_ECAM_SIZE, NULL);
> +
> +    return 0;
> +}
> +
> +/*
> + * Local variables:
> + * mode: C
> + * c-file-style: "BSD"
> + * c-basic-offset: 4
> + * indent-tabs-mode: nil
> + * End:
> + */
> +
> diff --git a/xen/arch/arm/vpci.h b/xen/arch/arm/vpci.h
> new file mode 100644
> index 0000000000..d8a7b0e3e8
> --- /dev/null
> +++ b/xen/arch/arm/vpci.h
> @@ -0,0 +1,36 @@
> +/*
> + * xen/arch/arm/vpci.h
> + *
> + * 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.
> + */
> +
> +#ifndef __ARCH_ARM_VPCI_H__
> +#define __ARCH_ARM_VPCI_H__
> +
> +#ifdef CONFIG_HAS_VPCI
> +int domain_vpci_init(struct domain *d);
> +#else
> +static inline int domain_vpci_init(struct domain *d)
> +{
> +    return 0;
> +}
> +#endif
> +
> +#endif /* __ARCH_ARM_VPCI_H__ */
> +
> +/*
> + * Local variables:
> + * mode: C
> + * c-file-style: "BSD"
> + * c-basic-offset: 4
> + * indent-tabs-mode: nil
> + * End:
> + */
> diff --git a/xen/drivers/passthrough/pci.c b/xen/drivers/passthrough/pci.c
> index 3aa8c3175f..8cc529ecec 100644
> --- a/xen/drivers/passthrough/pci.c
> +++ b/xen/drivers/passthrough/pci.c
> @@ -658,7 +658,7 @@ int pci_add_device(u16 seg, u8 bus, u8 devfn,
>                     const struct pci_dev_info *info, nodeid_t node)
>  {
>      struct pci_seg *pseg;
> -    struct pci_dev *pdev;
> +    struct pci_dev *pdev = NULL;
>      unsigned int slot = PCI_SLOT(devfn), func = PCI_FUNC(devfn);
>      const char *pdev_type;
>      int ret;
> @@ -752,6 +752,19 @@ int pci_add_device(u16 seg, u8 bus, u8 devfn,
>  
>      check_pdev(pdev);
>  
> +#ifdef CONFIG_ARM
> +    /*
> +     * On ARM PCI devices discovery will be done by Dom0. Add vpci handler 
> when
> +     * Dom0 inform XEN to add the PCI devices in XEN.
> +     */
> +    ret = vpci_add_handlers(pdev);
> +    if ( ret )
> +    {
> +        printk(XENLOG_ERR "Setup of vPCI failed: %d\n", ret);
> +        goto out;
> +    }
> +#endif

I think vpci_add_handlers should be called after checking that
pdev->domain is != NULL, so I would move this chunk a bit below.

> +
>      ret = 0;
>      if ( !pdev->domain )
>      {
> @@ -784,6 +797,9 @@ out:
>                     &PCI_SBDF(seg, bus, slot, func));
>          }
>      }
> +    else if ( pdev )
> +        pci_cleanup_msi(pdev);

I'm slightly lost at why you add this chunk, is this strictly related
to the patch?

>      return ret;
>  }
>  
> diff --git a/xen/drivers/vpci/header.c b/xen/drivers/vpci/header.c
> index f8cd55e7c0..c5b025b88b 100644
> --- a/xen/drivers/vpci/header.c
> +++ b/xen/drivers/vpci/header.c
> @@ -374,7 +374,8 @@ static void bar_write(const struct pci_dev *pdev, 
> unsigned int reg,
>          if ( val != (uint32_t)(bar->addr >> (hi ? 32 : 0)) )
>              gprintk(XENLOG_WARNING,
>                      "%pp: ignored BAR %lu write with memory decoding 
> enabled\n",
> -                    &pdev->sbdf, bar - pdev->vpci->header.bars + hi);
> +                    &pdev->sbdf,
> +                    (unsigned long)(bar - pdev->vpci->header.bars + hi));
>          return;
>      }
>  
> diff --git a/xen/drivers/vpci/vpci.c b/xen/drivers/vpci/vpci.c
> index c0853176d7..2bd67fc27a 100644
> --- a/xen/drivers/vpci/vpci.c
> +++ b/xen/drivers/vpci/vpci.c
> @@ -507,7 +507,7 @@ int vpci_ecam_mmio_write(pci_sbdf_t sbdf, unsigned int 
> reg, unsigned int len,
>  
>      vpci_write(sbdf, reg, min(4u, len), data);
>      if ( len == 8 )
> -        vpci_write(sbdf, reg + 4, 4, data >> 32);
> +        vpci_write(sbdf, reg + 4, 4, (uint64_t)data >> 32);
>  
>      return 1;
>  }
> diff --git a/xen/include/asm-arm/domain.h b/xen/include/asm-arm/domain.h
> index 14e575288f..9b3647587a 100644
> --- a/xen/include/asm-arm/domain.h
> +++ b/xen/include/asm-arm/domain.h
> @@ -263,6 +263,7 @@ static inline void arch_vcpu_block(struct vcpu *v) {}
>  
>  #define arch_vm_assist_valid_mask(d) (1UL << 
> VMASST_TYPE_runstate_update_flag)
>  
> +/* vPCI is not available on Arm */
>  #define has_vpci(d)    ({ (void)(d); false; })
>  
>  #endif /* __ASM_DOMAIN_H__ */
> diff --git a/xen/include/asm-x86/pci.h b/xen/include/asm-x86/pci.h
> index a0df5c1279..443f25347d 100644
> --- a/xen/include/asm-x86/pci.h
> +++ b/xen/include/asm-x86/pci.h
> @@ -6,8 +6,6 @@
>  #define CF8_ADDR_HI(cf8) (  ((cf8) & 0x0f000000) >> 16)
>  #define CF8_ENABLED(cf8) (!!((cf8) & 0x80000000))
>  
> -#define ECAM_BDF(addr)   ( ((addr) & 0x0ffff000) >> 12)
> -
>  #define IS_SNB_GFX(id) (id == 0x01068086 || id == 0x01168086 \
>                          || id == 0x01268086 || id == 0x01028086 \
>                          || id == 0x01128086 || id == 0x01228086 \
> diff --git a/xen/include/public/arch-arm.h b/xen/include/public/arch-arm.h
> index d46c61fca9..44be337dec 100644
> --- a/xen/include/public/arch-arm.h
> +++ b/xen/include/public/arch-arm.h
> @@ -418,6 +418,13 @@ typedef uint64_t xen_callback_t;
>  #define GUEST_GICV3_GICR0_BASE     xen_mk_ullong(0x03020000) /* vCPU0..127 */
>  #define GUEST_GICV3_GICR0_SIZE     xen_mk_ullong(0x01000000)
>  
> +/*
> + * 256 MB is reserved for VPCI configuration space based on calculation
> + * 256 buses × 32 devices × 8 functions × 4 KB = 256 MB
> + */
> +#define GUEST_VPCI_ECAM_BASE    xen_mk_ullong(0x10000000)
> +#define GUEST_VPCI_ECAM_SIZE    xen_mk_ullong(0x10000000)
> +
>  /* ACPI tables physical address */
>  #define GUEST_ACPI_BASE xen_mk_ullong(0x20000000)
>  #define GUEST_ACPI_SIZE xen_mk_ullong(0x02000000)
> diff --git a/xen/include/xen/pci.h b/xen/include/xen/pci.h
> index 70ac25345c..db18cb7639 100644
> --- a/xen/include/xen/pci.h
> +++ b/xen/include/xen/pci.h
> @@ -40,6 +40,9 @@
>  #define PCI_SBDF3(s,b,df) \
>      ((pci_sbdf_t){ .sbdf = (((s) & 0xffff) << 16) | PCI_BDF2(b, df) })
>  
> +#define ECAM_BDF(addr)         ( ((addr) & 0x0ffff000) >> 12)
                                   ^ extra space?

Thanks, Roger.