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SubjectRe: [PATCH v5 2/7] iommu/vt-d: Duplicate iommu_resv_region objects per device list
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Hi Eric,

On 5/28/19 7:50 PM, Eric Auger wrote:
> intel_iommu_get_resv_regions() aims to return the list of
> reserved regions accessible by a given @device. However several
> devices can access the same reserved memory region and when
> building the list it is not safe to use a single iommu_resv_region
> object, whose container is the RMRR. This iommu_resv_region must
> be duplicated per device reserved region list.
>
> Let's remove the struct iommu_resv_region from the RMRR unit
> and allocate the iommu_resv_region directly in
> intel_iommu_get_resv_regions(). We hold the dmar_global_lock instead
> of the rcu-lock to allow sleeping.
>
> Fixes: 0659b8dc45a6 ("iommu/vt-d: Implement reserved region get/put callbacks")
> Signed-off-by: Eric Auger <eric.auger@redhat.com>
>
> ---
>
> v4 -> v5
> - replace rcu-lock by the dmar_global_lock
> ---
> drivers/iommu/intel-iommu.c | 34 +++++++++++++++++-----------------
> 1 file changed, 17 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
> index a209199f3af6..5ec8b5bd308f 100644
> --- a/drivers/iommu/intel-iommu.c
> +++ b/drivers/iommu/intel-iommu.c
> @@ -322,7 +322,6 @@ struct dmar_rmrr_unit {
> u64 end_address; /* reserved end address */
> struct dmar_dev_scope *devices; /* target devices */
> int devices_cnt; /* target device count */
> - struct iommu_resv_region *resv; /* reserved region handle */
> };
>
> struct dmar_atsr_unit {
> @@ -4205,7 +4204,6 @@ static inline void init_iommu_pm_ops(void) {}
> int __init dmar_parse_one_rmrr(struct acpi_dmar_header *header, void *arg)
> {
> struct acpi_dmar_reserved_memory *rmrr;
> - int prot = DMA_PTE_READ|DMA_PTE_WRITE;
> struct dmar_rmrr_unit *rmrru;
> size_t length;
>
> @@ -4219,22 +4217,16 @@ int __init dmar_parse_one_rmrr(struct acpi_dmar_header *header, void *arg)
> rmrru->end_address = rmrr->end_address;
>
> length = rmrr->end_address - rmrr->base_address + 1;
> - rmrru->resv = iommu_alloc_resv_region(rmrr->base_address, length, prot,
> - IOMMU_RESV_DIRECT);
> - if (!rmrru->resv)
> - goto free_rmrru;
>
> rmrru->devices = dmar_alloc_dev_scope((void *)(rmrr + 1),
> ((void *)rmrr) + rmrr->header.length,
> &rmrru->devices_cnt);
> if (rmrru->devices_cnt && rmrru->devices == NULL)
> - goto free_all;
> + goto free_rmrru;
>
> list_add(&rmrru->list, &dmar_rmrr_units);
>
> return 0;
> -free_all:
> - kfree(rmrru->resv);
> free_rmrru:
> kfree(rmrru);
> out:
> @@ -4452,7 +4444,6 @@ static void intel_iommu_free_dmars(void)
> list_for_each_entry_safe(rmrru, rmrr_n, &dmar_rmrr_units, list) {
> list_del(&rmrru->list);
> dmar_free_dev_scope(&rmrru->devices, &rmrru->devices_cnt);
> - kfree(rmrru->resv);
> kfree(rmrru);
> }
>
> @@ -5470,22 +5461,33 @@ static void intel_iommu_remove_device(struct device *dev)
> static void intel_iommu_get_resv_regions(struct device *device,
> struct list_head *head)
> {
> + int prot = DMA_PTE_READ|DMA_PTE_WRITE;

I know this is moved from above. How about adding spaces around the '|'?

> struct iommu_resv_region *reg;
> struct dmar_rmrr_unit *rmrr;
> struct device *i_dev;
> int i;
>
> - rcu_read_lock();
> + down_write(&dmar_global_lock);

Just out of curiosity, why not down_read()? We don't change the rmrr
list here, right?

> for_each_rmrr_units(rmrr) {
> for_each_active_dev_scope(rmrr->devices, rmrr->devices_cnt,
> i, i_dev) {
> + struct iommu_resv_region *resv;
> + size_t length;
> +
> if (i_dev != device)
> continue;
>
> - list_add_tail(&rmrr->resv->list, head);
> + length = rmrr->end_address - rmrr->base_address + 1;
> + resv = iommu_alloc_resv_region(rmrr->base_address,
> + length, prot,
> + IOMMU_RESV_DIRECT);
> + if (!resv)
> + break;
> +
> + list_add_tail(&resv->list, head);
> }
> }
> - rcu_read_unlock();
> + up_write(&dmar_global_lock);
>
> reg = iommu_alloc_resv_region(IOAPIC_RANGE_START,
> IOAPIC_RANGE_END - IOAPIC_RANGE_START + 1,
> @@ -5500,10 +5502,8 @@ static void intel_iommu_put_resv_regions(struct device *dev,
> {
> struct iommu_resv_region *entry, *next;
>
> - list_for_each_entry_safe(entry, next, head, list) {
> - if (entry->type == IOMMU_RESV_MSI)
> - kfree(entry);
> - }
> + list_for_each_entry_safe(entry, next, head, list)
> + kfree(entry);
> }
>
> int intel_iommu_enable_pasid(struct intel_iommu *iommu, struct device *dev)
>

Other looks good to me.

Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>

Best regards,
Baolu

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