Re: [Xen-devel] [PATCH v4 10/12] IOMMU: introduce IOMMU_MIXED config option

[Julien Grall <julien.grall@xxxxxxx>]

Hi,

On 02/10/2018 11:18, Jan Beulich wrote:
> ARM is intended to gain support for heterogeneous IOMMUs on a single
> system. This not only disallows boot time replacement of respective
> indirect calls (handling of which is the main goal of the introduction
> here), but more generally disallows calls using the iommu_ops() return
> value directly - all such calls need to have means (commonly a domain
> pointer) to know the targeted IOMMU.
>
> Disallow all hooks lacking such context for the time being, which in
> effect is some dead code elimination for ARM. Once extended suitably,
> individual of these hooks can be moved out of their guards again in the
> future.
While in theory it is possible to have platform with hetereneous IOMMUs. 
 I don't see such such support coming in Xen for the foreseeable 
future. Note that even Linux does not support such case.
This patch is going to make more complicate to unshare page-tables as 
now we would need to care of mixed case. So I would rather not set 
IOMMU_MIXED on Arm until we have a use case for it.
Cheers,

> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> ---
> v4: New.
>
> --- a/xen/arch/arm/Kconfig
> +++ b/xen/arch/arm/Kconfig
> @@ -19,6 +19,7 @@ config ARM
>         select HAS_DEVICE_TREE
>         select HAS_PASSTHROUGH
>         select HAS_PDX
> +       select IOMMU_MIXED
>   
>   config ARCH_DEFCONFIG
>         string
> --- a/xen/common/memory.c
> +++ b/xen/common/memory.c
> @@ -938,7 +938,7 @@ static int construct_memop_from_reservat
>       return 0;
>   }
>   
> -#ifdef CONFIG_HAS_PASSTHROUGH
> +#if defined(CONFIG_HAS_PASSTHROUGH) && !defined(CONFIG_IOMMU_MIXED)
>   struct get_reserved_device_memory {
>       struct xen_reserved_device_memory_map map;
>       unsigned int used_entries;
> @@ -1550,7 +1550,7 @@ long do_memory_op(unsigned long cmd, XEN
>           break;
>       }
>   
> -#ifdef CONFIG_HAS_PASSTHROUGH
> +#if defined(CONFIG_HAS_PASSTHROUGH) && !defined(CONFIG_IOMMU_MIXED)
>       case XENMEM_reserved_device_memory_map:
>       {
>           struct get_reserved_device_memory grdm;
> --- a/xen/drivers/passthrough/Kconfig
> +++ b/xen/drivers/passthrough/Kconfig
> @@ -2,6 +2,9 @@
>   config HAS_PASSTHROUGH
>         bool
>   
> +config IOMMU_MIXED
> +       bool
> +
>   if ARM
>   config ARM_SMMU
>         bool "ARM SMMUv1 and v2 driver"
> --- a/xen/drivers/passthrough/iommu.c
> +++ b/xen/drivers/passthrough/iommu.c
> @@ -77,9 +77,11 @@ bool_t __read_mostly amd_iommu_perdev_in
>   
>   DEFINE_PER_CPU(bool_t, iommu_dont_flush_iotlb);
>   
> +#ifndef CONFIG_IOMMU_MIXED
>   DEFINE_SPINLOCK(iommu_pt_cleanup_lock);
>   PAGE_LIST_HEAD(iommu_pt_cleanup_list);
>   static struct tasklet iommu_pt_cleanup_tasklet;
> +#endif
>   
>   static int __init parse_iommu_param(const char *s)
>   {
> @@ -246,7 +248,9 @@ void iommu_teardown(struct domain *d)
>   
>       d->need_iommu = 0;
>       hd->platform_ops->teardown(d);
> +#ifndef CONFIG_IOMMU_MIXED
>       tasklet_schedule(&iommu_pt_cleanup_tasklet);
> +#endif
>   }
>   
>   int iommu_construct(struct domain *d)
> @@ -332,6 +336,7 @@ int iommu_unmap_page(struct domain *d, u
>       return rc;
>   }
>   
> +#ifndef CONFIG_IOMMU_MIXED
>   static void iommu_free_pagetables(unsigned long unused)
>   {
>       do {
> @@ -348,6 +353,7 @@ static void iommu_free_pagetables(unsign
>       tasklet_schedule_on_cpu(&iommu_pt_cleanup_tasklet,
>                               cpumask_cycle(smp_processor_id(), 
> &cpu_online_map));
>   }
> +#endif
>   
>   int iommu_iotlb_flush(struct domain *d, unsigned long gfn,
>                         unsigned int page_count)
> @@ -433,12 +439,15 @@ int __init iommu_setup(void)
>                  iommu_hwdom_passthrough ? "Passthrough" :
>                  iommu_hwdom_strict ? "Strict" : "Relaxed");
>           printk("Interrupt remapping %sabled\n", iommu_intremap ? "en" : 
> "dis");
> +#ifndef CONFIG_IOMMU_MIXED
>           tasklet_init(&iommu_pt_cleanup_tasklet, iommu_free_pagetables, 0);
> +#endif
>       }
>   
>       return rc;
>   }
>   
> +#ifndef CONFIG_IOMMU_MIXED
>   int iommu_suspend()
>   {
>       if ( iommu_enabled )
> @@ -453,27 +462,6 @@ void iommu_resume()
>           iommu_get_ops()->resume();
>   }
>   
> -int iommu_do_domctl(
> -    struct xen_domctl *domctl, struct domain *d,
> -    XEN_GUEST_HANDLE_PARAM(xen_domctl_t) u_domctl)
> -{
> -    int ret = -ENODEV;
> -
> -    if ( !iommu_enabled )
> -        return -ENOSYS;
> -
> -#ifdef CONFIG_HAS_PCI
> -    ret = iommu_do_pci_domctl(domctl, d, u_domctl);
> -#endif
> -
> -#ifdef CONFIG_HAS_DEVICE_TREE
> -    if ( ret == -ENODEV )
> -        ret = iommu_do_dt_domctl(domctl, d, u_domctl);
> -#endif
> -
> -    return ret;
> -}
> -
>   void iommu_share_p2m_table(struct domain* d)
>   {
>       if ( iommu_enabled && iommu_use_hap_pt(d) )
> @@ -500,6 +488,28 @@ int iommu_get_reserved_device_memory(iom
>   
>       return ops->get_reserved_device_memory(func, ctxt);
>   }
> +#endif
> +
> +int iommu_do_domctl(
> +    struct xen_domctl *domctl, struct domain *d,
> +    XEN_GUEST_HANDLE_PARAM(xen_domctl_t) u_domctl)
> +{
> +    int ret = -ENODEV;
> +
> +    if ( !iommu_enabled )
> +        return -ENOSYS;
> +
> +#ifdef CONFIG_HAS_PCI
> +    ret = iommu_do_pci_domctl(domctl, d, u_domctl);
> +#endif
> +
> +#ifdef CONFIG_HAS_DEVICE_TREE
> +    if ( ret == -ENODEV )
> +        ret = iommu_do_dt_domctl(domctl, d, u_domctl);
> +#endif
> +
> +    return ret;
> +}
>   
>   bool_t iommu_has_feature(struct domain *d, enum iommu_feature feature)
>   {
> --- a/xen/include/xen/iommu.h
> +++ b/xen/include/xen/iommu.h
> @@ -147,7 +147,7 @@ struct iommu_ops {
>       int (*assign_device)(struct domain *, u8 devfn, device_t *dev, u32 flag);
>       int (*reassign_device)(struct domain *s, struct domain *t,
>                              u8 devfn, device_t *dev);
> -#ifdef CONFIG_HAS_PCI
> +#if defined(CONFIG_HAS_PCI) && !defined(CONFIG_IOMMU_MIXED)
>       int (*get_device_group_id)(u16 seg, u8 bus, u8 devfn);
>       int (*update_ire_from_msi)(struct msi_desc *msi_desc, struct msi_msg 
> *msg);
>       void (*read_msi_from_ire)(struct msi_desc *msi_desc, struct msi_msg *msg);
> @@ -157,6 +157,7 @@ struct iommu_ops {
>       int __must_check (*map_page)(struct domain *d, unsigned long gfn,
>                                    unsigned long mfn, unsigned int flags);
>       int __must_check (*unmap_page)(struct domain *d, unsigned long gfn);
> +#ifndef CONFIG_IOMMU_MIXED
>       void (*free_page_table)(struct page_info *);
>   #ifdef CONFIG_X86
>       void (*update_ire_from_apic)(unsigned int apic, unsigned int reg, 
> unsigned int value);
> @@ -167,10 +168,11 @@ struct iommu_ops {
>       void (*resume)(void);
>       void (*share_p2m)(struct domain *d);
>       void (*crash_shutdown)(void);
> +    int (*get_reserved_device_memory)(iommu_grdm_t *, void *);
> +#endif
>       int __must_check (*iotlb_flush)(struct domain *d, unsigned long gfn,
>                                       unsigned int page_count);
>       int __must_check (*iotlb_flush_all)(struct domain *d);
> -    int (*get_reserved_device_memory)(iommu_grdm_t *, void *);
>       void (*dump_p2m_table)(struct domain *d);
>   };
>   
--
Julien Grall

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