From: <mhonap@nvidia.com>
To: <alex@shazbot.org>, <jgg@ziepe.ca>, <ankita@nvidia.com>,
<jic23@kernel.org>, <dave.jiang@intel.com>,
<alejandro.lucero-palau@amd.com>, <smadhavan@nvidia.com>,
<corbet@lwn.net>, <skhan@linuxfoundation.org>,
<dave@stgolabs.net>, <alison.schofield@intel.com>,
<vishal.l.verma@intel.com>, <iweiny@kernel.org>,
<ming.li@zohomail.com>, <yishaih@nvidia.com>,
<skolothumtho@nvidia.com>, <kevin.tian@intel.com>,
<bhelgaas@google.com>, <dmatlack@google.com>, <kees@kernel.org>,
<gustavoars@kernel.org>
Cc: <cjia@nvidia.com>, <kjaju@nvidia.com>, <vsethi@nvidia.com>,
<zhiw@nvidia.com>, <mhonap@nvidia.com>,
<linux-doc@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
<kvm@vger.kernel.org>, <linux-cxl@vger.kernel.org>,
<linux-pci@vger.kernel.org>, <linux-kselftest@vger.kernel.org>,
<linux-hardening@vger.kernel.org>
Subject: [PATCH v4 19/27] vfio/cxl: Keep the HDM decoder block off the direct BAR mapping
Date: Thu, 13 Aug 2026 15:06:23 +0530 [thread overview]
Message-ID: <20260813093631.2288172-20-mhonap@nvidia.com> (raw)
In-Reply-To: <20260813093631.2288172-1-mhonap@nvidia.com>
From: Manish Honap <mhonap@nvidia.com>
vfio-cxl owns the whole component BAR and serves the HDM decoder block
through a trapped region that runs the commit FSM against a shadow. Left
directly mmappable, the same block would let userspace reach the physical
decoder and move the host physical window. Exclude it from the BAR mmap so
the trap is the only path to it.
Signed-off-by: Manish Honap <mhonap@nvidia.com>
---
drivers/vfio/pci/cxl/vfio_cxl_core.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/drivers/vfio/pci/cxl/vfio_cxl_core.c b/drivers/vfio/pci/cxl/vfio_cxl_core.c
index 07047646edde..f91f6eb8b8fb 100644
--- a/drivers/vfio/pci/cxl/vfio_cxl_core.c
+++ b/drivers/vfio/pci/cxl/vfio_cxl_core.c
@@ -339,6 +339,14 @@ static int vfio_cxl_init_device(struct vfio_pci_core_device *vdev)
cxl->hdm_len = pdev->hdm->hdm_size;
+ /*
+ * The HDM decoder block is served from the trapped component-register
+ * region. Keep it out of the guest's direct BAR mapping so the physical
+ * decoder, which governs host memory decode, cannot be reprogrammed.
+ */
+ vfio_pci_core_set_mmap_exclude(vdev, pdev->hdm->hdm_bar,
+ pdev->hdm->hdm_offset, cxl->hdm_len);
+
ret = cxl_set_capacity(&cxl->cxlds, hdm_size);
if (ret)
return ret;
--
2.25.1
next prev parent reply other threads:[~2026-08-13 9:40 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-13 9:36 [PATCH v4 00/27] vfio/pci: Add CXL Type-2 device passthrough support mhonap
2026-08-13 9:36 ` [PATCH v4 01/27] cxl: Fix resource.c include path and export cxl_restore_hdm_after_pci_reset mhonap
2026-08-13 9:36 ` [PATCH v4 02/27] cxl/regs: Skip sub-block region request for BAR-owning drivers mhonap
2026-08-13 9:36 ` [PATCH v4 03/27] cxl: Move component register defines to uapi/cxl/cxl_regs.h mhonap
2026-08-13 9:36 ` [PATCH v4 04/27] cxl: Establish media readiness in cxl_mem_probe() mhonap
2026-08-13 9:36 ` [PATCH v4 05/27] cxl: Add a function-scoped reset entry for vfio-pci mhonap
2026-08-13 9:36 ` [PATCH v4 06/27] vfio/pci: Add CXL ops registration interface mhonap
2026-08-13 9:36 ` [PATCH v4 07/27] vfio/pci: Detect CXL devices and load vfio-cxl on demand mhonap
2026-08-13 9:36 ` [PATCH v4 08/27] vfio/cxl: Add the vfio-cxl module skeleton mhonap
2026-08-13 9:36 ` [PATCH v4 09/27] vfio/cxl: Create the CXL memory device at bind mhonap
2026-08-13 9:36 ` [PATCH v4 10/27] vfio/cxl: Reject unsupported decoder topologies " mhonap
2026-08-13 9:36 ` [PATCH v4 11/27] vfio/cxl: Own the whole component register BAR mhonap
2026-08-13 9:36 ` [PATCH v4 12/27] vfio/pci: Let a provider exclude a BAR sub-range from mmap mhonap
2026-08-13 9:36 ` [PATCH v4 13/27] vfio/pci: Refuse read/write to an excluded BAR sub-range mhonap
2026-08-13 9:36 ` [PATCH v4 14/27] vfio: Add CXL region type for the HDM region mhonap
2026-08-13 9:36 ` [PATCH v4 15/27] vfio/pci: Call CXL open and close hooks around device use mhonap
2026-08-13 9:36 ` [PATCH v4 16/27] vfio/cxl: Shadow the CXL DVSEC body at open mhonap
2026-08-13 9:36 ` [PATCH v4 17/27] vfio/cxl: Virtualize the CXL DVSEC mhonap
2026-08-13 9:36 ` [PATCH v4 18/27] vfio/cxl: Expose the HDM memory and trap the decoder registers mhonap
2026-08-13 9:36 ` mhonap [this message]
2026-08-13 9:36 ` [PATCH v4 20/27] vfio/cxl: Emulate the HDM decoder commit handshake mhonap
2026-08-13 9:36 ` [PATCH v4 21/27] vfio/cxl: Describe the CXL device and decoder geometry to userspace mhonap
2026-08-13 9:36 ` [PATCH v4 22/27] vfio/cxl: Revoke the HDM mapping on reset and power transitions mhonap
2026-08-13 9:36 ` [PATCH v4 23/27] vfio/cxl: Refresh the decoder snapshot after a device reset mhonap
2026-08-13 9:36 ` [PATCH v4 24/27] vfio/cxl: Service a guest-triggered CXL reset mhonap
2026-08-13 9:36 ` [PATCH v4 25/27] vfio/pci: Provide an opt-out for the CXL Type-2 extensions mhonap
2026-08-13 9:36 ` [PATCH v4 26/27] Documentation: vfio-pci: Document CXL Type-2 device passthrough mhonap
2026-08-13 9:36 ` [PATCH v4 27/27] selftests/vfio: Add CXL Type-2 passthrough corner-case tests mhonap
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