Re: [PATCH v2 14/18] IOMMU: fold flush-all hook into "flush one"

[Rahul Singh <Rahul.Singh@xxxxxxx>]

Hi Jan

> On 24 Sep 2021, at 10:53 am, Jan Beulich <jbeulich@xxxxxxxx> wrote:
> 
> Having a separate flush-all hook has always been puzzling me some. We
> will want to be able to force a full flush via accumulated flush flags
> from the map/unmap functions. Introduce a respective new flag and fold
> all flush handling to use the single remaining hook.
> 
> Note that because of the respective comments in SMMU and IPMMU-VMSA
> code, I've folded the two prior hook functions into one. For SMMU-v3,
> which lacks a comment towards incapable hardware, I've left both
> functions in place on the assumption that selective and full flushes
> will eventually want separating.


For SMMUv3 related Changs:
Reviewed-by: Rahul Singh <rahul.singh@xxxxxxx>

Regards,
Rahul
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> ---
> TBD: What we really are going to need is for the map/unmap functions to
>     specify that a wider region needs flushing than just the one
>     covered by the present set of (un)maps. This may still be less than
>     a full flush, but at least as a first step it seemed better to me
>     to keep things simple and go the flush-all route.
> ---
> v2: New.
> 
> --- a/xen/drivers/passthrough/amd/iommu.h
> +++ b/xen/drivers/passthrough/amd/iommu.h
> @@ -242,7 +242,6 @@ int amd_iommu_get_reserved_device_memory
> int __must_check amd_iommu_flush_iotlb_pages(struct domain *d, dfn_t dfn,
>                                              unsigned long page_count,
>                                              unsigned int flush_flags);
> -int __must_check amd_iommu_flush_iotlb_all(struct domain *d);
> void amd_iommu_print_entries(const struct amd_iommu *iommu, unsigned int 
> dev_id,
>                              dfn_t dfn);
> 
> --- a/xen/drivers/passthrough/amd/iommu_map.c
> +++ b/xen/drivers/passthrough/amd/iommu_map.c
> @@ -475,15 +475,18 @@ int amd_iommu_flush_iotlb_pages(struct d
> {
>     unsigned long dfn_l = dfn_x(dfn);
> 
> -    ASSERT(page_count && !dfn_eq(dfn, INVALID_DFN));
> -    ASSERT(flush_flags);
> +    if ( !(flush_flags & IOMMU_FLUSHF_all) )
> +    {
> +        ASSERT(page_count && !dfn_eq(dfn, INVALID_DFN));
> +        ASSERT(flush_flags);
> +    }
> 
>     /* Unless a PTE was modified, no flush is required */
>     if ( !(flush_flags & IOMMU_FLUSHF_modified) )
>         return 0;
> 
> -    /* If the range wraps then just flush everything */
> -    if ( dfn_l + page_count < dfn_l )
> +    /* If so requested or if the range wraps then just flush everything. */
> +    if ( (flush_flags & IOMMU_FLUSHF_all) || dfn_l + page_count < dfn_l )
>     {
>         amd_iommu_flush_all_pages(d);
>         return 0;
> @@ -508,13 +511,6 @@ int amd_iommu_flush_iotlb_pages(struct d
> 
>     return 0;
> }
> -
> -int amd_iommu_flush_iotlb_all(struct domain *d)
> -{
> -    amd_iommu_flush_all_pages(d);
> -
> -    return 0;
> -}
> 
> int amd_iommu_reserve_domain_unity_map(struct domain *d,
>                                        const struct ivrs_unity_map *map,
> --- a/xen/drivers/passthrough/amd/pci_amd_iommu.c
> +++ b/xen/drivers/passthrough/amd/pci_amd_iommu.c
> @@ -642,7 +642,6 @@ static const struct iommu_ops __initcons
>     .map_page = amd_iommu_map_page,
>     .unmap_page = amd_iommu_unmap_page,
>     .iotlb_flush = amd_iommu_flush_iotlb_pages,
> -    .iotlb_flush_all = amd_iommu_flush_iotlb_all,
>     .reassign_device = reassign_device,
>     .get_device_group_id = amd_iommu_group_id,
>     .enable_x2apic = iov_enable_xt,
> --- a/xen/drivers/passthrough/arm/ipmmu-vmsa.c
> +++ b/xen/drivers/passthrough/arm/ipmmu-vmsa.c
> @@ -930,13 +930,19 @@ out:
> }
> 
> /* Xen IOMMU ops */
> -static int __must_check ipmmu_iotlb_flush_all(struct domain *d)
> +static int __must_check ipmmu_iotlb_flush(struct domain *d, dfn_t dfn,
> +                                          unsigned long page_count,
> +                                          unsigned int flush_flags)
> {
>     struct ipmmu_vmsa_xen_domain *xen_domain = dom_iommu(d)->arch.priv;
> 
> +    ASSERT(flush_flags);
> +
>     if ( !xen_domain || !xen_domain->root_domain )
>         return 0;
> 
> +    /* The hardware doesn't support selective TLB flush. */
> +
>     spin_lock(&xen_domain->lock);
>     ipmmu_tlb_invalidate(xen_domain->root_domain);
>     spin_unlock(&xen_domain->lock);
> @@ -944,16 +950,6 @@ static int __must_check ipmmu_iotlb_flus
>     return 0;
> }
> 
> -static int __must_check ipmmu_iotlb_flush(struct domain *d, dfn_t dfn,
> -                                          unsigned long page_count,
> -                                          unsigned int flush_flags)
> -{
> -    ASSERT(flush_flags);
> -
> -    /* The hardware doesn't support selective TLB flush. */
> -    return ipmmu_iotlb_flush_all(d);
> -}
> -
> static struct ipmmu_vmsa_domain *ipmmu_get_cache_domain(struct domain *d,
>                                                         struct device *dev)
> {
> @@ -1303,7 +1299,6 @@ static const struct iommu_ops ipmmu_iomm
>     .hwdom_init      = ipmmu_iommu_hwdom_init,
>     .teardown        = ipmmu_iommu_domain_teardown,
>     .iotlb_flush     = ipmmu_iotlb_flush,
> -    .iotlb_flush_all = ipmmu_iotlb_flush_all,
>     .assign_device   = ipmmu_assign_device,
>     .reassign_device = ipmmu_reassign_device,
>     .map_page        = arm_iommu_map_page,
> --- a/xen/drivers/passthrough/arm/smmu.c
> +++ b/xen/drivers/passthrough/arm/smmu.c
> @@ -2649,11 +2649,17 @@ static int force_stage = 2;
>  */
> static u32 platform_features = ARM_SMMU_FEAT_COHERENT_WALK;
> 
> -static int __must_check arm_smmu_iotlb_flush_all(struct domain *d)
> +static int __must_check arm_smmu_iotlb_flush(struct domain *d, dfn_t dfn,
> +                                          unsigned long page_count,
> +                                          unsigned int flush_flags)
> {
>       struct arm_smmu_xen_domain *smmu_domain = dom_iommu(d)->arch.priv;
>       struct iommu_domain *cfg;
> 
> +     ASSERT(flush_flags);
> +
> +     /* ARM SMMU v1 doesn't have flush by VMA and VMID */
> +
>       spin_lock(&smmu_domain->lock);
>       list_for_each_entry(cfg, &smmu_domain->contexts, list) {
>               /*
> @@ -2670,16 +2676,6 @@ static int __must_check arm_smmu_iotlb_f
>       return 0;
> }
> 
> -static int __must_check arm_smmu_iotlb_flush(struct domain *d, dfn_t dfn,
> -                                          unsigned long page_count,
> -                                          unsigned int flush_flags)
> -{
> -     ASSERT(flush_flags);
> -
> -     /* ARM SMMU v1 doesn't have flush by VMA and VMID */
> -     return arm_smmu_iotlb_flush_all(d);
> -}
> -
> static struct iommu_domain *arm_smmu_get_domain(struct domain *d,
>                                               struct device *dev)
> {
> @@ -2879,7 +2875,6 @@ static const struct iommu_ops arm_smmu_i
>     .add_device = arm_smmu_dt_add_device_generic,
>     .teardown = arm_smmu_iommu_domain_teardown,
>     .iotlb_flush = arm_smmu_iotlb_flush,
> -    .iotlb_flush_all = arm_smmu_iotlb_flush_all,
>     .assign_device = arm_smmu_assign_dev,
>     .reassign_device = arm_smmu_reassign_dev,
>     .map_page = arm_iommu_map_page,
> --- a/xen/drivers/passthrough/arm/smmu-v3.c
> +++ b/xen/drivers/passthrough/arm/smmu-v3.c
> @@ -3431,7 +3431,6 @@ static const struct iommu_ops arm_smmu_i
>       .hwdom_init             = arm_smmu_iommu_hwdom_init,
>       .teardown               = arm_smmu_iommu_xen_domain_teardown,
>       .iotlb_flush            = arm_smmu_iotlb_flush,
> -     .iotlb_flush_all        = arm_smmu_iotlb_flush_all,
>       .assign_device          = arm_smmu_assign_dev,
>       .reassign_device        = arm_smmu_reassign_dev,
>       .map_page               = arm_iommu_map_page,
> --- a/xen/drivers/passthrough/iommu.c
> +++ b/xen/drivers/passthrough/iommu.c
> @@ -463,15 +463,12 @@ int iommu_iotlb_flush_all(struct domain
>     const struct domain_iommu *hd = dom_iommu(d);
>     int rc;
> 
> -    if ( !is_iommu_enabled(d) || !hd->platform_ops->iotlb_flush_all ||
> +    if ( !is_iommu_enabled(d) || !hd->platform_ops->iotlb_flush ||
>          !flush_flags )
>         return 0;
> 
> -    /*
> -     * The operation does a full flush so we don't need to pass the
> -     * flush_flags in.
> -     */
> -    rc = iommu_call(hd->platform_ops, iotlb_flush_all, d);
> +    rc = iommu_call(hd->platform_ops, iotlb_flush, d, INVALID_DFN, 0,
> +                    flush_flags | IOMMU_FLUSHF_all);
>     if ( unlikely(rc) )
>     {
>         if ( !d->is_shutting_down && printk_ratelimit() )
> --- a/xen/drivers/passthrough/vtd/iommu.c
> +++ b/xen/drivers/passthrough/vtd/iommu.c
> @@ -731,18 +731,21 @@ static int __must_check iommu_flush_iotl
>                                                 unsigned long page_count,
>                                                 unsigned int flush_flags)
> {
> -    ASSERT(page_count && !dfn_eq(dfn, INVALID_DFN));
> -    ASSERT(flush_flags);
> +    if ( flush_flags & IOMMU_FLUSHF_all )
> +    {
> +        dfn = INVALID_DFN;
> +        page_count = 0;
> +    }
> +    else
> +    {
> +        ASSERT(page_count && !dfn_eq(dfn, INVALID_DFN));
> +        ASSERT(flush_flags);
> +    }
> 
>     return iommu_flush_iotlb(d, dfn, flush_flags & IOMMU_FLUSHF_modified,
>                              page_count);
> }
> 
> -static int __must_check iommu_flush_iotlb_all(struct domain *d)
> -{
> -    return iommu_flush_iotlb(d, INVALID_DFN, 0, 0);
> -}
> -
> static void queue_free_pt(struct domain *d, mfn_t mfn, unsigned int 
> next_level)
> {
>     if ( next_level > 1 )
> @@ -2841,7 +2844,7 @@ static int __init intel_iommu_quarantine
>     spin_unlock(&hd->arch.mapping_lock);
> 
>     if ( !rc )
> -        rc = iommu_flush_iotlb_all(d);
> +        rc = iommu_flush_iotlb(d, INVALID_DFN, 0, 0);
> 
>     /* Pages may be leaked in failure case */
>     return rc;
> @@ -2874,7 +2877,6 @@ static struct iommu_ops __initdata vtd_o
>     .resume = vtd_resume,
>     .crash_shutdown = vtd_crash_shutdown,
>     .iotlb_flush = iommu_flush_iotlb_pages,
> -    .iotlb_flush_all = iommu_flush_iotlb_all,
>     .get_reserved_device_memory = intel_iommu_get_reserved_device_memory,
>     .dump_page_tables = vtd_dump_page_tables,
> };
> --- a/xen/include/xen/iommu.h
> +++ b/xen/include/xen/iommu.h
> @@ -147,9 +147,11 @@ enum
> {
>     _IOMMU_FLUSHF_added,
>     _IOMMU_FLUSHF_modified,
> +    _IOMMU_FLUSHF_all,
> };
> #define IOMMU_FLUSHF_added (1u << _IOMMU_FLUSHF_added)
> #define IOMMU_FLUSHF_modified (1u << _IOMMU_FLUSHF_modified)
> +#define IOMMU_FLUSHF_all (1u << _IOMMU_FLUSHF_all)
> 
> int __must_check iommu_map(struct domain *d, dfn_t dfn, mfn_t mfn,
>                            unsigned long page_count, unsigned int flags,
> @@ -282,7 +284,6 @@ struct iommu_ops {
>     int __must_check (*iotlb_flush)(struct domain *d, dfn_t dfn,
>                                     unsigned long page_count,
>                                     unsigned int flush_flags);
> -    int __must_check (*iotlb_flush_all)(struct domain *d);
>     int (*get_reserved_device_memory)(iommu_grdm_t *, void *);
>     void (*dump_page_tables)(struct domain *d);
> 
>