On 2021-05-26 17:36, Shameerali Kolothum Thodi wrote:

quoted

-----Original Message-----
From: Laurentiu Tudor [mailto:laurentiu.tudor@nxp.com]
Sent: 26 May 2021 08:53
To: Shameerali Kolothum Thodi <redacted>;
linux-arm-kernel@lists.infradead.org; linux-acpi@vger.kernel.org;
iommu@lists.linux-foundation.org
Cc: jon@solid-run.com; Linuxarm <redacted>;
steven.price@arm.com; Guohanjun (Hanjun Guo) [off-list ref];
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robin.murphy@arm.com; wanghuiqiang [off-list ref]
Subject: Re: [PATCH v5 3/8] ACPI/IORT: Add a helper to retrieve RMR memory
regions

Hi Shameer,

On 5/24/2021 2:02 PM, Shameer Kolothum wrote:

quoted

Add a helper function that retrieves RMR memory descriptors
associated with a given IOMMU. This will be used by IOMMU
drivers to setup necessary mappings.

Now that we have this, invoke it from the generic helper
interface.

Signed-off-by: Shameer Kolothum

[off-list ref]

quoted

---
  drivers/acpi/arm64/iort.c | 50

+++++++++++++++++++++++++++++++++++++++

quoted

  drivers/iommu/dma-iommu.c |  4 ++++
  include/linux/acpi_iort.h |  7 ++++++
  3 files changed, 61 insertions(+)

diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c
index fea1ffaedf3b..01917caf58de 100644
--- a/drivers/acpi/arm64/iort.c
+++ b/drivers/acpi/arm64/iort.c

@@ -12,6 +12,7 @@

  #include <linux/acpi_iort.h>
  #include <linux/bitfield.h>
+#include <linux/dma-iommu.h>
  #include <linux/iommu.h>
  #include <linux/kernel.h>
  #include <linux/list.h>

@@ -837,6 +838,53 @@ static inline int iort_add_device_replay(struct

device *dev)

quoted

  	return err;
  }

+/**
+ * iort_iommu_get_rmrs - Helper to retrieve RMR info associated with

IOMMU

quoted

+ * @iommu: fwnode for the IOMMU
+ * @head: RMR list head to be populated
+ *
+ * Returns: 0 on success, <0 failure
+ */
+int iort_iommu_get_rmrs(struct fwnode_handle *iommu_fwnode,
+			struct list_head *head)
+{
+	struct iort_rmr_entry *e;
+	struct acpi_iort_node *iommu;
+	int rmrs = 0;
+
+	iommu = iort_get_iort_node(iommu_fwnode);
+	if (!iommu || list_empty(&iort_rmr_list))
+		return -ENODEV;
+
+	list_for_each_entry(e, &iort_rmr_list, list) {
+		int prot = IOMMU_READ | IOMMU_WRITE | IOMMU_NOEXEC |

IOMMU_MMIO;

We have a case with an IP block that needs EXEC rights on its reserved
memory, so could you please drop the IOMMU_NOEXEC flag?

Ok, I think I can drop that one if there are no other concerns. I was not quite
sure what to include here in the first place as the IORT spec is not giving any
further details about the RMR regions(May be the flags field can be extended to
describe these details).

Right, it's reserved for the device to use *somehow* - that's all we 
know, so it's not our place to try and enforce any restrictive 
permissions. All it could possibly achieve is the ability to log an 
error to say "a thing did an unknown thing in a way we didn't expect!", 
and there's hardly much value in that.

Robin.

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