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X-MS-Exchange-CrossTenant-Id: 4e2c6054-71cb-48f1-bd6c-3a9705aca71b X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: 7sIz1R0f2T83DE3EBJvgCqcl6/kFaqssTeLB1XF9VT8NKP9Dc1lPPrDQK/H89WYRwywOMQvvnwg1LfELX7aMxaYyXNpJq30lhK43eyDZLoY= X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA1PR10MB7684 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1039,Hydra:6.0.650,FMLib:17.12.28.16 definitions=2024-05-22_10,2024-05-22_01,2024-05-17_01 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 adultscore=0 mlxscore=0 mlxlogscore=999 phishscore=0 bulkscore=0 suspectscore=0 malwarescore=0 spamscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2405010000 definitions=main-2405220128 X-Proofpoint-ORIG-GUID: sJzjXkT7IJfnx2QQotsePm20loGe2miV X-Proofpoint-GUID: sJzjXkT7IJfnx2QQotsePm20loGe2miV On 22/05/2024 19:15, Joao Martins wrote: > On 22/05/2024 18:50, Jason Gunthorpe wrote: >> On Wed, May 22, 2024 at 06:10:59PM +0100, Joao Martins wrote: >>> On 22/05/2024 17:56, Jason Gunthorpe wrote: >>>> On Wed, May 22, 2024 at 03:37:57PM +0100, Joao Martins wrote: >>>> >>>>> This is just to catch the case where IOMMUFD can call into read_and_clear() >>>>> without dirty tracking enabled and without a bitmap structure to clear dirty >>>>> bits -- in order to ensure a clean PTE data snapshot after start(). >>>> >>>> Is that broken then? >>>> >>> >>> It's not: The check errors out the caller ends up calling read-and-clear with a >>> bitmap but without having started dirty tracking. the iopt_clear_dirty_data() >>> passes a null bitmap, it goes through and it walks and clears the IOPTEs >>> *without* recording them in the bitmap. >> >> It is not "without recording them in the bitmap", saying that is the >> confusing thing. The purpose of that 'if' is to return -EINVAL if >> dirty tracking is not turned on and we query the bitmap. >> > Right. > >> More like this puts it in the common code and writes it in a more >> straightforward way with better locking: >> > Yes, This snip you pasted would be the equivalent to the current way indeed. > Looks good > > I think I was trying too hard not to duplicate 'state of dirty tracking' between > iommu driver and iommufd core that I unintendedly ended up convoluting with this > check in the driver :/ > To this point above (...) >> diff --git a/drivers/iommu/iommufd/io_pagetable.c b/drivers/iommu/iommufd/io_pagetable.c >> index 05fd9d3abf1b80..d116179809042d 100644 >> --- a/drivers/iommu/iommufd/io_pagetable.c >> +++ b/drivers/iommu/iommufd/io_pagetable.c >> @@ -536,7 +536,10 @@ int iopt_read_and_clear_dirty_data(struct io_pagetable *iopt, >> return ret; >> >> down_read(&iopt->iova_rwsem); >> - ret = iommu_read_and_clear_dirty(domain, iopt, flags, bitmap); >> + if (!iopt->dirty_tracking_enabled) >> + ret = -EINVAL; >> + else >> + ret = iommu_read_and_clear_dirty(domain, iopt, flags, bitmap); >> up_read(&iopt->iova_rwsem); >> >> return ret; >> @@ -580,7 +583,11 @@ int iopt_set_dirty_tracking(struct io_pagetable *iopt, >> if (!ops) >> return -EOPNOTSUPP; >> >> - down_read(&iopt->iova_rwsem); >> + down_write(&iopt->iova_rwsem); >> + if (iopt->dirty_tracking_enabled == enable) { >> + ret = 0; >> + goto out_unlock; >> + } >> We have a similar check in set_dirty_tracking iommu op of intel/amd iommu drivers that could be removed. Though I am not sure it's right to remove it even as we move this up the stack >> /* Clear dirty bits from PTEs to ensure a clean snapshot */ >> if (enable) { >> @@ -590,9 +597,11 @@ int iopt_set_dirty_tracking(struct io_pagetable *iopt, >> } >> >> ret = ops->set_dirty_tracking(domain, enable); >> - >> + if (ret) >> + goto out_unlock; >> + iopt->dirty_tracking_enabled = enable; >> out_unlock: >> - up_read(&iopt->iova_rwsem); >> + up_write(&iopt->iova_rwsem); >> return ret; >> } >> >> diff --git a/drivers/iommu/iommufd/iommufd_private.h b/drivers/iommu/iommufd/iommufd_private.h >> index 991f864d1f9bc1..de3761e15cab54 100644 >> --- a/drivers/iommu/iommufd/iommufd_private.h >> +++ b/drivers/iommu/iommufd/iommufd_private.h >> @@ -52,6 +52,7 @@ struct io_pagetable { >> /* IOVA that cannot be allocated, struct iopt_reserved */ >> struct rb_root_cached reserved_itree; >> u8 disable_large_pages; >> + u8 dirty_tracking_enabled; >> unsigned long iova_alignment; >> }; >> >