From: Jason Gunthorpe <jgg@ziepe.ca>
To: Dan Williams <djbw@kernel.org>
Cc: mhonap@nvidia.com, alwilliamson@nvidia.com,
jonathan.cameron@huawei.com, dave.jiang@intel.com,
alejandro.lucero-palau@amd.com, dave@stgolabs.net,
alison.schofield@intel.com, vishal.l.verma@intel.com,
ira.weiny@intel.com, dmatlack@google.com, shuah@kernel.org,
yishaih@nvidia.com, skolothumtho@nvidia.com,
kevin.tian@intel.com, ankita@nvidia.com, vsethi@nvidia.com,
cjia@nvidia.com, targupta@nvidia.com, zhiw@nvidia.com,
kjaju@nvidia.com, linux-kselftest@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-cxl@vger.kernel.org,
kvm@vger.kernel.org
Subject: Re: [PATCH v2 16/20] vfio/cxl: Register regions with VFIO layer
Date: Mon, 6 Apr 2026 19:10:25 -0300 [thread overview]
Message-ID: <20260406221025.GH2551565@ziepe.ca> (raw)
In-Reply-To: <69d1685538f45_556821002f@djbw-dev.notmuch>
On Sat, Apr 04, 2026 at 12:36:53PM -0700, Dan Williams wrote:
> Then I assume it matters that memremap() sometimes silently falls back
> to the direct map. The "VFIO owns" expectation needs to guard against
> some helpful platform firmware mapping accelerator memory as System RAM.
I don't think how memremap works under the covers matters to vfio, it
takes in a phys_addr_t an gives back a KVA that is cachable kernel
memory.
We just have to be mindful to not allow mismatched attributes on
virtual aliases.
> At a minimum having VFIO fail to map in that case helps with the
> argument I have been making that "no, EFI_CONVENTIONAL_MEMORY type +
> EFI_SPECIFIC_PURPOSE flag" is not suitable for accelerators with private
> CXL memory. Those want to be enforcing "EFI_RESERVED".
Certainly it should fail the request region if something else is using
it, so if those EFI flags plug it into the mm and it is plugged when
VFIO starts then it should stop.
The direct map isn't really "plugged into the mm" but it does raise
the mismatched attributed issue.
Jason
next prev parent reply other threads:[~2026-04-06 22:10 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-04-01 14:38 [PATCH v2 00/20] vfio/pci: Add CXL Type-2 device passthrough support mhonap
2026-04-01 14:38 ` [PATCH v2 01/20] cxl: Add cxl_get_hdm_info() for HDM decoder metadata mhonap
2026-04-01 14:38 ` [PATCH v2 02/20] cxl: Declare cxl_find_regblock and cxl_probe_component_regs in public header mhonap
2026-04-01 14:39 ` [PATCH v2 03/20] cxl: Move component/HDM register defines to uapi/cxl/cxl_regs.h mhonap
2026-04-01 14:39 ` [PATCH v2 04/20] cxl: Split cxl_await_range_active() from media-ready wait mhonap
2026-04-01 14:39 ` [PATCH v2 05/20] cxl: Record BIR and BAR offset in cxl_register_map mhonap
2026-04-01 14:39 ` [PATCH v2 06/20] vfio: UAPI for CXL-capable PCI device assignment mhonap
2026-04-01 14:39 ` [PATCH v2 07/20] vfio/pci: Add CXL state to vfio_pci_core_device mhonap
2026-04-01 14:39 ` [PATCH v2 08/20] vfio/pci: Add CONFIG_VFIO_CXL_CORE and stub CXL hooks mhonap
2026-04-01 14:39 ` [PATCH v2 09/20] vfio/cxl: Detect CXL DVSEC and probe HDM block mhonap
2026-04-01 14:39 ` [PATCH v2 10/20] vfio/pci: Export config access helpers mhonap
2026-04-01 14:39 ` [PATCH v2 11/20] vfio/cxl: Introduce HDM decoder register emulation framework mhonap
2026-04-01 14:39 ` [PATCH v2 12/20] vfio/cxl: Wait for HDM ranges and create memdev mhonap
2026-04-01 14:39 ` [PATCH v2 13/20] vfio/cxl: CXL region management support mhonap
2026-04-01 14:39 ` [PATCH v2 14/20] vfio/cxl: DPA VFIO region with demand fault mmap and reset zap mhonap
2026-04-01 14:39 ` [PATCH v2 15/20] vfio/cxl: Virtualize CXL DVSEC config writes mhonap
2026-04-01 14:39 ` [PATCH v2 16/20] vfio/cxl: Register regions with VFIO layer mhonap
2026-04-03 19:35 ` Dan Williams
2026-04-04 18:53 ` Jason Gunthorpe
2026-04-04 19:36 ` Dan Williams
2026-04-06 21:22 ` Gregory Price
2026-04-06 22:05 ` Jason Gunthorpe
2026-04-07 14:15 ` Gregory Price
2026-04-06 22:10 ` Jason Gunthorpe [this message]
2026-04-01 14:39 ` [PATCH v2 17/20] vfio/pci: Advertise CXL cap and sparse component BAR to userspace mhonap
2026-04-01 14:39 ` [PATCH v2 18/20] vfio/cxl: Provide opt-out for CXL feature mhonap
2026-04-01 14:39 ` [PATCH v2 19/20] docs: vfio-pci: Document CXL Type-2 device passthrough mhonap
2026-04-01 14:39 ` [PATCH v2 20/20] selftests/vfio: Add CXL Type-2 VFIO assignment test mhonap
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