[PATCH v2 10/11] vfio/pci: Hide stolen memory from the user

[Alex Williamson <alex.williamson@redhat.com>]

We do not provide a way for the user to access the host stolen memory
therefore hide both the base address and the size.  This is mostly
useful for VM users where the driver may try to make use of the memory
referenced by these registers, whether the VM considers it reserved
for the GPU or not.

Unfortunately the format of the GMCH_CTRL register is not constant
between chip revisions, so we're stuck with ongoing maintenance to try
to track the latest device IDs.  Perhaps if the register is stable now
we should blacklist pre-SandyBridge devices, identify the old format
for Gen 6 and 7 devices, and assume anything else uses Gen 8 format.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---
 drivers/vfio/pci/vfio_pci_igd.c |   80 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 80 insertions(+)

diff --git a/drivers/vfio/pci/vfio_pci_igd.c b/drivers/vfio/pci/vfio_pci_igd.c
index 6394b16..03d916e 100644
--- a/drivers/vfio/pci/vfio_pci_igd.c
+++ b/drivers/vfio/pci/vfio_pci_igd.c
@@ -18,11 +18,15 @@
 #include <linux/uaccess.h>
 #include <linux/vfio.h>
 
+#include <drm/i915_drm.h>
+#include <drm/i915_pciids.h>
+
 #include "vfio_pci_private.h"
 
 #define OPREGION_SIGNATURE	"IntelGraphicsMem"
 #define OPREGION_SIZE		(8 * 1024)
 #define OPREGION_PCI_ADDR	0xfc
+#define BDSM_PCI_ADDR		0x5c /* Base Data Stolen Memory */
 
 static size_t vfio_pci_igd_rw(struct vfio_pci_device *vdev, char __user *buf,
 			      size_t count, loff_t *ppos, bool iswrite)
@@ -264,8 +268,64 @@ static int vfio_pci_igd_cfg_init(struct vfio_pci_device *vdev)
 	return 0;
 }
 
+struct vfio_pci_igd_info {
+	u16 gmch_gsm_mask;
+};
+
+static const struct vfio_pci_igd_info igd_gen6 = {
+	.gmch_gsm_mask = SNB_GMCH_GMS_MASK << SNB_GMCH_GMS_SHIFT,
+};
+
+static const struct vfio_pci_igd_info igd_gen8 = {
+	.gmch_gsm_mask = BDW_GMCH_GMS_MASK << BDW_GMCH_GMS_SHIFT,
+};
+
+static const struct pci_device_id vfio_pci_igd_ids[] = {
+	/* Gen6 - SandyBridge */
+	INTEL_SNB_D_IDS(&igd_gen6),
+	INTEL_SNB_M_IDS(&igd_gen6),
+	/* Gen7 - IvyBridge, ValleyView, Haswell */
+	INTEL_IVB_D_IDS(&igd_gen6),
+	INTEL_IVB_M_IDS(&igd_gen6),
+	INTEL_IVB_Q_IDS(&igd_gen6),
+	INTEL_VLV_M_IDS(&igd_gen6),
+	INTEL_VLV_D_IDS(&igd_gen6),
+	INTEL_HSW_D_IDS(&igd_gen6),
+	INTEL_HSW_M_IDS(&igd_gen6),
+	/* Gen8 - BroadWell, CherryView */
+	INTEL_BDW_GT12D_IDS(&igd_gen8),
+	INTEL_BDW_GT12M_IDS(&igd_gen8),
+	INTEL_BDW_GT3D_IDS(&igd_gen8),
+	INTEL_BDW_GT3M_IDS(&igd_gen8),
+	INTEL_CHV_IDS(&igd_gen8),
+	/* Gen9 - SkyLake, Broxton, KabyLake */
+	INTEL_SKL_GT1_IDS(&igd_gen8),
+	INTEL_SKL_GT2_IDS(&igd_gen8),
+	INTEL_SKL_GT3_IDS(&igd_gen8),
+	INTEL_SKL_GT4_IDS(&igd_gen8),
+	INTEL_BXT_IDS(&igd_gen8),
+	INTEL_KBL_GT1_IDS(&igd_gen8),
+	INTEL_KBL_GT2_IDS(&igd_gen8),
+	INTEL_KBL_GT3_IDS(&igd_gen8),
+	INTEL_KBL_GT4_IDS(&igd_gen8),
+	{ 0 }
+};
+
+static struct vfio_pci_igd_info *vfio_pci_igd_info(struct pci_dev *pdev)
+{
+	const struct pci_device_id *id;
+
+	id = pci_match_id(vfio_pci_igd_ids, pdev);
+	if (!id)
+		return NULL;
+
+	return (struct vfio_pci_igd_info *)id->driver_data;
+}
+
 int vfio_pci_igd_init(struct vfio_pci_device *vdev)
 {
+	struct vfio_pci_igd_info *info;
+	u16 gmch;
 	int ret;
 
 	ret = vfio_pci_igd_opregion_init(vdev);
@@ -276,5 +336,25 @@ int vfio_pci_igd_init(struct vfio_pci_device *vdev)
 	if (ret)
 		return ret;
 
+	memset(vdev->vconfig + BDSM_PCI_ADDR, 0, 4);
+	memset(vdev->pci_config_map + BDSM_PCI_ADDR,
+	       PCI_CAP_ID_INVALID_VIRT, 4);
+
+	info = vfio_pci_igd_info(vdev->pdev);
+	if (!info) {
+		dev_warn(&vdev->pdev->dev,
+			 "Unknown/Unsupported Intel IGD device\n");
+		return 0;
+	}
+
+	ret = pci_read_config_word(vdev->pdev, SNB_GMCH_CTRL, &gmch);
+	if (ret)
+		return ret;
+
+	gmch &= ~info->gmch_gsm_mask;
+	*(__le16 *)(vdev->vconfig + SNB_GMCH_CTRL) = cpu_to_le16(gmch);
+	memset(vdev->pci_config_map + SNB_GMCH_CTRL,
+	       PCI_CAP_ID_INVALID_VIRT, 2);
+
 	return 0;
 }