Re: [PATCH v13 09/14] iommu/ipmmu-vmsa: Implement suspend/resume callbacks

[Bertrand Marquis <Bertrand.Marquis@xxxxxxx>]

Hi Mykola,

> On 27 Oct 2026, at 22:05, Mykola Kvach <mykola_kvach@xxxxxxxx> wrote:
> 
> From: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
> 
> Store and restore active context and micro-TLB registers.
> 
> On resume, restore Root IPMMU context state before restoring Cache IPMMU
> micro-TLB state. Cache IPMMUs select Root contexts through their micro-TLB
> configuration, so restoring Cache micro-TLBs before the Root context
> registers are restored can expose stale or uninitialized context state.
> 
> Tested only on H3ULCB (R-Car Gen3).
> 
> Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
> Signed-off-by: Mykola Kvach <mykola_kvach@xxxxxxxx>
> Reviewed-by: Luca Fancellu <luca.fancellu@xxxxxxx>

Acked-by: Bertrand Marquis <bertrand.marquis@xxxxxxx>

Cheers
Bertrand

> ---
> Changes in V13:
> - State that suspend/resume was tested only on H3ULCB (R-Car Gen3).
> 
> Changes in V10:
> - Iterate over registered IPMMUs in reverse order during resume so Root IPMMU
>  context state is restored before Cache IPMMU micro-TLB state.
> 
> Changes in V9:
> - set dt_device_set_protected() only after ipmmu_alloc_ctx_suspend()
>  succeeds, so DT devices do not remain protected on allocation failure.
> 
> Changes in V7:
> - moved suspend context allocation before pci stuff
> ---
> xen/drivers/passthrough/arm/ipmmu-vmsa.c | 323 +++++++++++++++++++++--
> 1 file changed, 308 insertions(+), 15 deletions(-)
> 
> diff --git a/xen/drivers/passthrough/arm/ipmmu-vmsa.c 
> b/xen/drivers/passthrough/arm/ipmmu-vmsa.c
> index fa9ab9cb13..2e54fa63d6 100644
> --- a/xen/drivers/passthrough/arm/ipmmu-vmsa.c
> +++ b/xen/drivers/passthrough/arm/ipmmu-vmsa.c
> @@ -71,6 +71,8 @@
> })
> #endif
> 
> +#define dev_dbg(dev, fmt, ...)    \
> +    dev_print(dev, XENLOG_DEBUG, fmt, ## __VA_ARGS__)
> #define dev_info(dev, fmt, ...)    \
>     dev_print(dev, XENLOG_INFO, fmt, ## __VA_ARGS__)
> #define dev_warn(dev, fmt, ...)    \
> @@ -130,6 +132,24 @@ struct ipmmu_features {
>     unsigned int imuctr_ttsel_mask;
> };
> 
> +#ifdef CONFIG_SYSTEM_SUSPEND
> +
> +struct ipmmu_reg_ctx {
> +    unsigned int imttlbr0;
> +    unsigned int imttubr0;
> +    unsigned int imttbcr;
> +    unsigned int imctr;
> +};
> +
> +struct ipmmu_vmsa_backup {
> +    struct device *dev;
> +    unsigned int *utlbs_val;
> +    unsigned int *asids_val;
> +    struct list_head list;
> +};
> +
> +#endif
> +
> /* Root/Cache IPMMU device's information */
> struct ipmmu_vmsa_device {
>     struct device *dev;
> @@ -142,6 +162,9 @@ struct ipmmu_vmsa_device {
>     struct ipmmu_vmsa_domain *domains[IPMMU_CTX_MAX];
>     unsigned int utlb_refcount[IPMMU_UTLB_MAX];
>     const struct ipmmu_features *features;
> +#ifdef CONFIG_SYSTEM_SUSPEND
> +    struct ipmmu_reg_ctx *reg_backup[IPMMU_CTX_MAX];
> +#endif
> };
> 
> /*
> @@ -547,6 +570,249 @@ static void ipmmu_domain_free_context(struct 
> ipmmu_vmsa_device *mmu,
>     spin_unlock_irqrestore(&mmu->lock, flags);
> }
> 
> +#ifdef CONFIG_SYSTEM_SUSPEND
> +
> +static DEFINE_SPINLOCK(ipmmu_devices_backup_lock);
> +static LIST_HEAD(ipmmu_devices_backup);
> +
> +static struct ipmmu_reg_ctx root_pgtable[IPMMU_CTX_MAX];
> +
> +static uint32_t ipmmu_imuasid_read(struct ipmmu_vmsa_device *mmu,
> +                                   unsigned int utlb)
> +{
> +    return ipmmu_read(mmu, ipmmu_utlb_reg(mmu, IMUASID(utlb)));
> +}
> +
> +static void ipmmu_utlbs_backup(struct ipmmu_vmsa_device *mmu)
> +{
> +    struct ipmmu_vmsa_backup *backup_data;
> +
> +    dev_dbg(mmu->dev, "Handle micro-TLBs backup\n");
> +
> +    spin_lock(&ipmmu_devices_backup_lock);
> +
> +    list_for_each_entry( backup_data, &ipmmu_devices_backup, list )
> +    {
> +        struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(backup_data->dev);
> +        unsigned int i;
> +
> +        if ( to_ipmmu(backup_data->dev) != mmu )
> +            continue;
> +
> +        for ( i = 0; i < fwspec->num_ids; i++ )
> +        {
> +            unsigned int utlb = fwspec->ids[i];
> +
> +            backup_data->asids_val[i] = ipmmu_imuasid_read(mmu, utlb);
> +            backup_data->utlbs_val[i] = ipmmu_imuctr_read(mmu, utlb);
> +        }
> +    }
> +
> +    spin_unlock(&ipmmu_devices_backup_lock);
> +}
> +
> +static void ipmmu_utlbs_restore(struct ipmmu_vmsa_device *mmu)
> +{
> +    struct ipmmu_vmsa_backup *backup_data;
> +
> +    dev_dbg(mmu->dev, "Handle micro-TLBs restore\n");
> +
> +    spin_lock(&ipmmu_devices_backup_lock);
> +
> +    list_for_each_entry( backup_data, &ipmmu_devices_backup, list )
> +    {
> +        struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(backup_data->dev);
> +        unsigned int i;
> +
> +        if ( to_ipmmu(backup_data->dev) != mmu )
> +            continue;
> +
> +        for ( i = 0; i < fwspec->num_ids; i++ )
> +        {
> +            unsigned int utlb = fwspec->ids[i];
> +
> +            ipmmu_imuasid_write(mmu, utlb, backup_data->asids_val[i]);
> +            ipmmu_imuctr_write(mmu, utlb, backup_data->utlbs_val[i]);
> +        }
> +    }
> +
> +    spin_unlock(&ipmmu_devices_backup_lock);
> +}
> +
> +static void ipmmu_domain_backup_context(struct ipmmu_vmsa_domain *domain)
> +{
> +    struct ipmmu_vmsa_device *mmu = domain->mmu->root;
> +    struct ipmmu_reg_ctx *regs = mmu->reg_backup[domain->context_id];
> +
> +    dev_dbg(mmu->dev, "Handle domain context %u backup\n", 
> domain->context_id);
> +
> +    regs->imttlbr0 = ipmmu_ctx_read_root(domain, IMTTLBR0);
> +    regs->imttubr0 = ipmmu_ctx_read_root(domain, IMTTUBR0);
> +    regs->imttbcr  = ipmmu_ctx_read_root(domain, IMTTBCR);
> +    regs->imctr    = ipmmu_ctx_read_root(domain, IMCTR);
> +}
> +
> +static void ipmmu_domain_restore_context(struct ipmmu_vmsa_domain *domain)
> +{
> +    struct ipmmu_vmsa_device *mmu = domain->mmu->root;
> +    struct ipmmu_reg_ctx *regs = mmu->reg_backup[domain->context_id];
> +
> +    dev_dbg(mmu->dev, "Handle domain context %u restore\n", 
> domain->context_id);
> +
> +    ipmmu_ctx_write_root(domain, IMTTLBR0, regs->imttlbr0);
> +    ipmmu_ctx_write_root(domain, IMTTUBR0, regs->imttubr0);
> +    ipmmu_ctx_write_root(domain, IMTTBCR,  regs->imttbcr);
> +    ipmmu_ctx_write_all(domain,  IMCTR,    regs->imctr | IMCTR_FLUSH);
> +}
> +
> +/*
> + * Xen: Unlike Linux implementation, Xen uses a single driver instance
> + * for handling all IPMMUs. There is no framework for ipmmu_suspend/resume
> + * callbacks to be invoked for each IPMMU device. So, we need to iterate
> + * through all registered IPMMUs performing required actions.
> + *
> + * Also take care of restoring special settings, such as translation
> + * table format, etc.
> + */
> +static int __must_check ipmmu_suspend(void)
> +{
> +    struct ipmmu_vmsa_device *mmu;
> +
> +    if ( !iommu_enabled )
> +        return 0;
> +
> +    printk(XENLOG_DEBUG "ipmmu: Suspending...\n");
> +
> +    spin_lock(&ipmmu_devices_lock);
> +
> +    list_for_each_entry( mmu, &ipmmu_devices, list )
> +    {
> +        if ( ipmmu_is_root(mmu) )
> +        {
> +            unsigned int i;
> +
> +            for ( i = 0; i < mmu->num_ctx; i++ )
> +            {
> +                if ( !mmu->domains[i] )
> +                    continue;
> +                ipmmu_domain_backup_context(mmu->domains[i]);
> +            }
> +        }
> +        else
> +            ipmmu_utlbs_backup(mmu);
> +    }
> +
> +    spin_unlock(&ipmmu_devices_lock);
> +
> +    return 0;
> +}
> +
> +static void ipmmu_resume(void)
> +{
> +    struct ipmmu_vmsa_device *mmu;
> +
> +    if ( !iommu_enabled )
> +        return;
> +
> +    printk(XENLOG_DEBUG "ipmmu: Resuming...\n");
> +
> +    spin_lock(&ipmmu_devices_lock);
> +
> +    /*
> +     * IPMMUs are registered with list_add(), with Root IPMMU probed first.
> +     * Walk backwards to restore Root contexts before Cache micro-TLBs.
> +     */
> +    list_for_each_entry_reverse( mmu, &ipmmu_devices, list )
> +    {
> +        uint32_t reg;
> +
> +        /* Do not use security group function */
> +        reg = IMSCTLR + mmu->features->control_offset_base;
> +        ipmmu_write(mmu, reg, ipmmu_read(mmu, reg) & ~IMSCTLR_USE_SECGRP);
> +
> +        if ( ipmmu_is_root(mmu) )
> +        {
> +            unsigned int i;
> +
> +            /* Use stage 2 translation table format */
> +            reg = IMSAUXCTLR + mmu->features->control_offset_base;
> +            ipmmu_write(mmu, reg, ipmmu_read(mmu, reg) | IMSAUXCTLR_S2PTE);
> +
> +            for ( i = 0; i < mmu->num_ctx; i++ )
> +            {
> +                if ( !mmu->domains[i] )
> +                    continue;
> +                ipmmu_domain_restore_context(mmu->domains[i]);
> +            }
> +        }
> +        else
> +            ipmmu_utlbs_restore(mmu);
> +    }
> +
> +    spin_unlock(&ipmmu_devices_lock);
> +}
> +
> +static int ipmmu_alloc_ctx_suspend(struct device *dev)
> +{
> +    struct ipmmu_vmsa_backup *backup_data;
> +    unsigned int *utlbs_val, *asids_val;
> +    struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev);
> +
> +    utlbs_val = xzalloc_array(unsigned int, fwspec->num_ids);
> +    if ( !utlbs_val )
> +        return -ENOMEM;
> +
> +    asids_val = xzalloc_array(unsigned int, fwspec->num_ids);
> +    if ( !asids_val )
> +    {
> +        xfree(utlbs_val);
> +        return -ENOMEM;
> +    }
> +
> +    backup_data = xzalloc(struct ipmmu_vmsa_backup);
> +    if ( !backup_data )
> +    {
> +        xfree(utlbs_val);
> +        xfree(asids_val);
> +        return -ENOMEM;
> +    }
> +
> +    backup_data->dev = dev;
> +    backup_data->utlbs_val = utlbs_val;
> +    backup_data->asids_val = asids_val;
> +
> +    spin_lock(&ipmmu_devices_backup_lock);
> +    list_add(&backup_data->list, &ipmmu_devices_backup);
> +    spin_unlock(&ipmmu_devices_backup_lock);
> +
> +    return 0;
> +}
> +
> +#ifdef CONFIG_HAS_PCI
> +static void ipmmu_free_ctx_suspend(struct device *dev)
> +{
> +    struct ipmmu_vmsa_backup *backup_data, *tmp;
> +
> +    spin_lock(&ipmmu_devices_backup_lock);
> +
> +    list_for_each_entry_safe( backup_data, tmp, &ipmmu_devices_backup, list )
> +    {
> +        if ( backup_data->dev == dev )
> +        {
> +            list_del(&backup_data->list);
> +            xfree(backup_data->utlbs_val);
> +            xfree(backup_data->asids_val);
> +            xfree(backup_data);
> +            break;
> +        }
> +    }
> +
> +    spin_unlock(&ipmmu_devices_backup_lock);
> +}
> +#endif /* CONFIG_HAS_PCI */
> +
> +#endif /* CONFIG_SYSTEM_SUSPEND */
> +
> static int ipmmu_domain_init_context(struct ipmmu_vmsa_domain *domain)
> {
>     uint64_t ttbr;
> @@ -559,6 +825,9 @@ static int ipmmu_domain_init_context(struct 
> ipmmu_vmsa_domain *domain)
>         return ret;
> 
>     domain->context_id = ret;
> +#ifdef CONFIG_SYSTEM_SUSPEND
> +    domain->mmu->root->reg_backup[ret] = &root_pgtable[ret];
> +#endif
> 
>     /*
>      * TTBR0
> @@ -615,6 +884,9 @@ static void ipmmu_domain_destroy_context(struct 
> ipmmu_vmsa_domain *domain)
>     ipmmu_ctx_write_root(domain, IMCTR, IMCTR_FLUSH);
>     ipmmu_tlb_sync(domain);
> 
> +#ifdef CONFIG_SYSTEM_SUSPEND
> +    domain->mmu->root->reg_backup[domain->context_id] = NULL;
> +#endif
>     ipmmu_domain_free_context(domain->mmu->root, domain->context_id);
> }
> 
> @@ -1338,10 +1610,11 @@ static int ipmmu_add_device(u8 devfn, struct device 
> *dev)
>     struct iommu_fwspec *fwspec;
> 
> #ifdef CONFIG_HAS_PCI
> +    int ret;
> +
>     if ( dev_is_pci(dev) )
>     {
>         struct pci_dev *pdev = dev_to_pci(dev);
> -        int ret;
> 
>         if ( devfn != pdev->devfn )
>             return 0;
> @@ -1358,17 +1631,24 @@ static int ipmmu_add_device(u8 devfn, struct device 
> *dev)
>     if ( !to_ipmmu(dev) )
>         return -ENODEV;
> 
> -    if ( !dev_is_pci(dev) )
> +    if ( !dev_is_pci(dev) && dt_device_is_protected(dev_to_dt(dev)) )
>     {
> -        if ( dt_device_is_protected(dev_to_dt(dev)) )
> -        {
> -            dev_err(dev, "Already added to IPMMU\n");
> -            return -EEXIST;
> -        }
> +        dev_err(dev, "Already added to IPMMU\n");
> +        return -EEXIST;
> +    }
> 
> -        /* Let Xen know that the master device is protected by an IOMMU. */
> -        dt_device_set_protected(dev_to_dt(dev));
> +#ifdef CONFIG_SYSTEM_SUSPEND
> +    if ( ipmmu_alloc_ctx_suspend(dev) )
> +    {
> +        dev_err(dev, "Failed to allocate context for suspend\n");
> +        return -ENOMEM;
>     }
> +#endif
> +
> +    /* Let Xen know that the master device is protected by an IOMMU. */
> +    if ( !dev_is_pci(dev) )
> +        dt_device_set_protected(dev_to_dt(dev));
> +
> #ifdef CONFIG_HAS_PCI
>     if ( dev_is_pci(dev) )
>     {
> @@ -1377,26 +1657,28 @@ static int ipmmu_add_device(u8 devfn, struct device 
> *dev)
>         struct pci_host_bridge *bridge;
>         struct iommu_fwspec *fwspec_bridge;
>         unsigned int utlb_osid0 = 0;
> -        int ret;
> 
>         bridge = pci_find_host_bridge(pdev->seg, pdev->bus);
>         if ( !bridge )
>         {
>             dev_err(dev, "Failed to find host bridge\n");
> -            return -ENODEV;
> +            ret = -ENODEV;
> +            goto free_suspend_ctx;
>         }
> 
>         fwspec_bridge = dev_iommu_fwspec_get(dt_to_dev(bridge->dt_node));
>         if ( fwspec_bridge->num_ids < 1 )
>         {
>             dev_err(dev, "Failed to find host bridge uTLB\n");
> -            return -ENXIO;
> +            ret = -ENXIO;
> +            goto free_suspend_ctx;
>         }
> 
>         if ( fwspec->num_ids < 1 )
>         {
>             dev_err(dev, "Failed to find uTLB");
> -            return -ENXIO;
> +            ret = -ENXIO;
> +            goto free_suspend_ctx;
>         }
> 
>         rcar4_pcie_osid_regs_init(bridge);
> @@ -1405,7 +1687,7 @@ static int ipmmu_add_device(u8 devfn, struct device 
> *dev)
>         if ( ret < 0 )
>         {
>             dev_err(dev, "No unused OSID regs\n");
> -            return ret;
> +            goto free_suspend_ctx;
>         }
>         reg_id = ret;
> 
> @@ -1420,7 +1702,7 @@ static int ipmmu_add_device(u8 devfn, struct device 
> *dev)
>         {
>             rcar4_pcie_osid_bdf_clear(bridge, reg_id);
>             rcar4_pcie_osid_reg_free(bridge, reg_id);
> -            return ret;
> +            goto free_suspend_ctx;
>         }
>     }
> #endif
> @@ -1429,6 +1711,13 @@ static int ipmmu_add_device(u8 devfn, struct device 
> *dev)
>              dev_name(fwspec->iommu_dev), fwspec->num_ids);
> 
>     return 0;
> +#ifdef CONFIG_HAS_PCI
> + free_suspend_ctx:
> +#ifdef CONFIG_SYSTEM_SUSPEND
> +    ipmmu_free_ctx_suspend(dev);
> +#endif
> +    return ret;
> +#endif
> }
> 
> static int ipmmu_iommu_domain_init(struct domain *d)
> @@ -1490,6 +1779,10 @@ static const struct iommu_ops ipmmu_iommu_ops =
>     .unmap_page      = arm_iommu_unmap_page,
>     .dt_xlate        = ipmmu_dt_xlate,
>     .add_device      = ipmmu_add_device,
> +#ifdef CONFIG_SYSTEM_SUSPEND
> +    .suspend         = ipmmu_suspend,
> +    .resume          = ipmmu_resume,
> +#endif
> };
> 
> static __init int ipmmu_init(struct dt_device_node *node, const void *data)
> -- 
> 2.53.0
>