Hi Julien,
> On 7 Mar 2025, at 09:09, Julien Grall <jul...@xen.org> wrote:
>
> Hi Luca,
>
> On 07/03/2025 07:58, Luca Fancellu wrote:
>> When Xen is built without HAS_PASSTHROUGH, there are some parts
>> in arm where iommu_* functions are called in the codebase, but
>> their implementation is under xen/drivers/passthrough that is
>> not built.
>> So provide some stub for these functions in order to build Xen
>> when !HAS_PASSTHROUGH, which is the case for example on systems
>> with MPU support.
>> For gnttab_need_iommu_mapping() in the Arm part, modify the macro
>> to use IS_ENABLED for the HAS_PASSTHROUGH Kconfig.
>> Fixes: 0388a5979b21 ("xen/arm: mpu: Introduce choice between MMU and MPU")
>> Signed-off-by: Luca Fancellu <luca.fance...@arm.com>
>> ---
>> v4 changes:
>> - re-introduced stub for iommu_use_hap_pt, Stefano suggested
>> it is ok to have it in iommu.h.
>> - Reworded comment in iommu_domain_init from Jan suggestion
>> v3 Changes:
>> - removed stub for iommu_use_hap_pt, another solution will be
>> done for the instance in common arm code.
>> - Moved a comment close to the macro it was referred to
>> - add comment to iommu_domain_init() stub
>> - modified commit message
>> - Add fixes tag
>> v2 Changes:
>> - modify gnttab_need_iommu_mapping to use IS_ENABLED
>> - removed macro that didn't allow some of the parameter to be
>> evaluated
>> - Changed commit message
>> ---
>> ---
>> xen/arch/arm/include/asm/grant_table.h | 5 +--
>> xen/include/xen/iommu.h | 50 +++++++++++++++++++++++++-
>> 2 files changed, 52 insertions(+), 3 deletions(-)
>> diff --git a/xen/arch/arm/include/asm/grant_table.h
>> b/xen/arch/arm/include/asm/grant_table.h
>> index d3c518a926b9..c5d87b60c4df 100644
>> --- a/xen/arch/arm/include/asm/grant_table.h
>> +++ b/xen/arch/arm/include/asm/grant_table.h
>> @@ -73,8 +73,9 @@ int replace_grant_host_mapping(uint64_t gpaddr, mfn_t
>> frame,
>> #define gnttab_status_gfn(d, t, i) \
>> page_get_xenheap_gfn(gnttab_status_page(t, i))
>> -#define gnttab_need_iommu_mapping(d) \
>> - (is_domain_direct_mapped(d) && is_iommu_enabled(d))
>> +#define gnttab_need_iommu_mapping(d) \
>> + (IS_ENABLED(CONFIG_HAS_PASSTHROUGH) && is_domain_direct_mapped(d) && \
>> + is_iommu_enabled(d))
>> #endif /* __ASM_GRANT_TABLE_H__ */
>> /*
>> diff --git a/xen/include/xen/iommu.h b/xen/include/xen/iommu.h
>> index 77a514019cc6..5ac038521e23 100644
>> --- a/xen/include/xen/iommu.h
>> +++ b/xen/include/xen/iommu.h
>> @@ -110,6 +110,8 @@ extern int8_t iommu_hwdom_reserved;
>> extern unsigned int iommu_dev_iotlb_timeout;
>> +#ifdef CONFIG_HAS_PASSTHROUGH
>> +
>> int iommu_setup(void);
>> int iommu_hardware_setup(void);
>> @@ -122,6 +124,28 @@ int arch_iommu_domain_init(struct domain *d);
>> void arch_iommu_check_autotranslated_hwdom(struct domain *d);
>> void arch_iommu_hwdom_init(struct domain *d);
>> +#else
>> +
>> +static inline int iommu_setup(void)
>> +{
>> + return -ENODEV;
>> +}
>> +
>> +static inline int iommu_domain_init(struct domain *d, unsigned int opts)
>> +{
>> + /*
>> + * Return as the real iommu_domain_init() would: Success when
>> + * !is_iommu_enabled(), following from !iommu_enabled when
>> !HAS_PASSTHROUGH
>> + */
>> + return 0;
>> +}
>> +
>> +static inline void iommu_hwdom_init(struct domain *d) {}
>> +
>> +static inline void iommu_domain_destroy(struct domain *d) {}
>> +
>> +#endif /* HAS_PASSTHROUGH */
>> +
>> /*
>> * The following flags are passed to map (applicable ones also to unmap)
>> * operations, while some are passed back by lookup operations.
>> @@ -209,6 +233,8 @@ struct msi_msg;
>> #ifdef CONFIG_HAS_DEVICE_TREE
>> #include <xen/device_tree.h>
>> +#ifdef CONFIG_HAS_PASSTHROUGH
>> +
>> int iommu_assign_dt_device(struct domain *d, struct dt_device_node *dev);
>> int iommu_deassign_dt_device(struct domain *d, struct dt_device_node *dev);
>> int iommu_dt_domain_init(struct domain *d);
>> @@ -238,6 +264,26 @@ int iommu_do_dt_domctl(struct xen_domctl *domctl,
>> struct domain *d,
>> */
>> int iommu_remove_dt_device(struct dt_device_node *np);
>> +#else
>> +
>> +static inline int iommu_assign_dt_device(struct domain *d,
>> + struct dt_device_node *dev)
>> +{
>> + return -EINVAL;
>> +}
>> +
>> +static inline int iommu_add_dt_device(struct dt_device_node *np)
>> +{
>> + return 1;
>
> I would suggest to add a comment explain what 1 means. IIRC, this means "no
> iommu" present.
Would it be ok something like in iommu_domain_init:
/*
* Returns as the real iommu_add_dt_device() would: Error “no iommu" because
* !iommu_enabled due to the fact that !HAS_PASSTHROUGH
*/
>
> Other than that:
>
> Acked-by: Julien Grall <jgr...@amazon.com>
>
> Cheers,
>
> --
> Julien Grall
>
