Hi Cédric,
>-----Original Message-----
>From: Cédric Le Goater <c...@redhat.com>
>Subject: Re: [PATCH v1 1/6] backends/iommufd: Add a helper to invalidate user-
>managed HWPT
>
>Hello Zhenzhong,
>
>On 5/28/25 08:04, Zhenzhong Duan wrote:
>> This helper passes cache invalidation request from guest to invalidate
>> stage-1 page table cache in host hardware.
>>
>> Signed-off-by: Nicolin Chen <nicol...@nvidia.com>
>> Signed-off-by: Zhenzhong Duan <zhenzhong.d...@intel.com>
>> ---
>> include/system/iommufd.h | 4 ++++
>> backends/iommufd.c | 33 +++++++++++++++++++++++++++++++++
>> backends/trace-events | 1 +
>> 3 files changed, 38 insertions(+)
>>
>> diff --git a/include/system/iommufd.h b/include/system/iommufd.h
>> index cbab75bfbf..5399519626 100644
>> --- a/include/system/iommufd.h
>> +++ b/include/system/iommufd.h
>> @@ -61,6 +61,10 @@ bool
>iommufd_backend_get_dirty_bitmap(IOMMUFDBackend *be, uint32_t hwpt_id,
>> uint64_t iova, ram_addr_t size,
>> uint64_t page_size, uint64_t *data,
>> Error **errp);
>> +bool iommufd_backend_invalidate_cache(IOMMUFDBackend *be, uint32_t id,
>> + uint32_t data_type, uint32_t
>> entry_len,
>> + uint32_t *entry_num, void *data_ptr,
>> + Error **errp);
>>
>> #define TYPE_HOST_IOMMU_DEVICE_IOMMUFD
>TYPE_HOST_IOMMU_DEVICE "-iommufd"
>> #endif
>> diff --git a/backends/iommufd.c b/backends/iommufd.c
>> index b73f75cd0b..c8788a6438 100644
>> --- a/backends/iommufd.c
>> +++ b/backends/iommufd.c
>> @@ -311,6 +311,39 @@ bool
>iommufd_backend_get_device_info(IOMMUFDBackend *be, uint32_t devid,
>> return true;
>> }
>>
>> +bool iommufd_backend_invalidate_cache(IOMMUFDBackend *be, uint32_t id,
>> + uint32_t data_type, uint32_t
>> entry_len,
>> + uint32_t *entry_num, void *data_ptr,
>> + Error **errp)
>> +{
>> + int ret, fd = be->fd;
>> + uint32_t total_entries = *entry_num;
>> + struct iommu_hwpt_invalidate cache = {
>> + .size = sizeof(cache),
>> + .hwpt_id = id,
>> + .data_type = data_type,
>> + .entry_len = entry_len,
>> + .entry_num = total_entries,
>> + .data_uptr = (uintptr_t)data_ptr,
>
>Minor, other helpers use a 'data' variable name.
Will do.
>
>> + };
>> +
>> + ret = ioctl(fd, IOMMU_HWPT_INVALIDATE, &cache);
>> + trace_iommufd_backend_invalidate_cache(fd, id, data_type, entry_len,
>> + total_entries, cache.entry_num,
>> + (uintptr_t)data_ptr,
>> + ret ? errno : 0);
>> + if (ret) {
>> + *entry_num = cache.entry_num;
>> + error_setg_errno(errp, errno, "IOMMU_HWPT_INVALIDATE failed:"
>> + " totally %d entries, processed %d entries",
>> + total_entries, cache.entry_num);
>> + } else {
>> + g_assert(total_entries == cache.entry_num);
>
>Killing the VMM because a kernel device ioctl failed is brute force.
>Can't we update the 'Error *' parameter instead to report that the
>invalidation is partial or something went wrong ?
Will do, like below:
--- a/backends/iommufd.c
+++ b/backends/iommufd.c
@@ -339,7 +339,10 @@ bool iommufd_backend_invalidate_cache(IOMMUFDBackend *be,
uint32_t id,
" totally %d entries, processed %d entries",
total_entries, cache.entry_num);
} else {
- g_assert(total_entries == cache.entry_num);
+ error_setg_errno(errp, -EFAULT, "IOMMU_HWPT_INVALIDATE succeed with
unprocessed entries:"
+ " totally %d entries, processed %d entries",
+ total_entries, cache.entry_num);
+ ret = -EFAULT;
}
return !ret;
>
>What kind of errors are we trying to catch ?
I'm taking it as a kernel bug when ret = 0 and total_entries != cache.entry_num
>
>Looking at the kernel iommufd_hwpt_invalidate() routine and
>intel_nested_cache_invalidate_user(), it doesn't seem possible to
>return a different number of cache entries. Are you anticipating
>other implementations (sMMU) ?
Yes, same for sMMU's arm_vsmmu_cache_invalidate() and selftest's
mock_viommu_cache_invalidate() and mock_domain_cache_invalidate_user().
I'm not sure if this should apply to all types of IOMMUs, uAPI doc doesn't talk
about it.
@Liu, Yi L, @nicol...@nvidia.com, @Jason Gunthorpe, should I treat ret = 0 and
total_entries != cache.entry_num as a kernel bug or not?
Thanks
Zhenzhong
