From: Nicolin Chen <nicolinc@nvidia.com>
To: Jason Gunthorpe <jgg@nvidia.com>
Cc: <kevin.tian@intel.com>, <shuah@kernel.org>,
<joao.m.martins@oracle.com>, <steven.sistare@oracle.com>,
<iommu@lists.linux.dev>, <linux-kselftest@vger.kernel.org>,
<linux-kernel@vger.kernel.org>, <thomas.weissschuh@linutronix.de>
Subject: Re: [PATCH rc 1/4] iommufd/selftest: Fix iommufd_dirty_tracking with large hugepage sizes
Date: Tue, 17 Jun 2025 16:46:57 -0700 [thread overview]
Message-ID: <aFH+cUSi1GITvF3F@nvidia.com> (raw)
In-Reply-To: <20250617230136.GC1575786@nvidia.com>
On Tue, Jun 17, 2025 at 08:01:36PM -0300, Jason Gunthorpe wrote:
> On Tue, Jun 17, 2025 at 02:23:41PM -0700, Nicolin Chen wrote:
> > On Tue, Jun 17, 2025 at 08:59:48AM -0300, Jason Gunthorpe wrote:
> > > On Mon, Jun 16, 2025 at 07:02:08PM -0700, Nicolin Chen wrote:
> > > > ---breakdown---
> > > > After `posix_memalign()`:
> > > > [ posix_memalign() memory ] ← malloc thinks it owns this
> > > >
> > > > Then `mmap(aligned_ptr, ..., MAP_FIXED)`:
> > > > [ anonymous mmap region ] ← malloc still thinks it owns this (!)
> > > > ↑ mapped
> > > > ---end---
> > >
> > > Yes, this is correct and what we are doing here. The allocator always
> > > owns it and we are just replacing the memory with a different mmap.
> >
> > Hmm, if allocator always owns it. Does that mean the munmap() [3]
> > will release what [1] and [2] do (allocating and replacing)?
>
> No, munmap doesn't destroy the allocator meta data.
Should we do something to that meta data?
next prev parent reply other threads:[~2025-06-17 23:47 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-06-16 5:02 [PATCH rc 0/4] Fix iommufd selftest FAIL and warnings with v6.16 Nicolin Chen
2025-06-16 5:02 ` [PATCH rc 1/4] iommufd/selftest: Fix iommufd_dirty_tracking with large hugepage sizes Nicolin Chen
2025-06-16 16:25 ` Jason Gunthorpe
2025-06-17 2:02 ` Nicolin Chen
2025-06-17 11:59 ` Jason Gunthorpe
2025-06-17 21:23 ` Nicolin Chen
2025-06-17 23:01 ` Jason Gunthorpe
2025-06-17 23:46 ` Nicolin Chen [this message]
2025-06-18 11:38 ` Jason Gunthorpe
2025-06-16 5:02 ` [PATCH rc 2/4] iommufd/selftest: Add missing close(mfd) in memfd_mmap() Nicolin Chen
2025-06-16 16:25 ` Jason Gunthorpe
2025-06-16 5:02 ` [PATCH rc 3/4] iommufd/selftest: Add asserts testing global mfd Nicolin Chen
2025-06-16 16:26 ` Jason Gunthorpe
2025-06-16 5:02 ` [PATCH rc 4/4] iommufd/selftest: Fix build warnings due to uninitialized mfd Nicolin Chen
2025-06-16 16:27 ` Jason Gunthorpe
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