platform/x86/intel/pmt: allow user offset for PMT callbacks

JIRA: https://issues.redhat.com/browse/RHEL-85955

commit 0c32840
Author: Michael J. Ruhl <michael.j.ruhl@intel.com>
Date:   Thu Nov 14 08:03:57 2024 -0500

    platform/x86/intel/pmt: allow user offset for PMT callbacks

    Usage of the telem sysfs file allows for partial reads at an offset.
    The current callback method returns the buffer starting from offset 0
    only.

    Include the requested offset in the callback and update the necessary
    address calculations with the offset.

    Note: offset addition is moved from the caller to the local usage. For
    non-callback usage this is unchanged behavior.

    Fixes: e92affc ("platform/x86/intel/vsec: Add PMT read callbacks")
    Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
    Signed-off-by: Michael J. Ruhl <michael.j.ruhl@intel.com>
    Link: https://lore.kernel.org/r/20241114130358.2467787-2-michael.j.ruhl@intel.com
    Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
    Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

Signed-off-by: José Expósito <jexposit@redhat.com>

Author: jexposit

drivers/platform/x86/intel/pmt/class.c

@@ -59,10 +59,12 @@ pmt_memcpy64_fromio(void *to, const u64 __iomem *from, size_t count)
 }
 
 int pmt_telem_read_mmio(struct pci_dev *pdev, struct pmt_callbacks *cb, u32 guid, void *buf,
-			void __iomem *addr, u32 count)
+			void __iomem *addr, loff_t off, u32 count)
 {
 	if (cb && cb->read_telem)
-		return cb->read_telem(pdev, guid, buf, count);
+		return cb->read_telem(pdev, guid, buf, off, count);
+
+	addr += off;
 
 	if (guid == GUID_SPR_PUNIT)
 		/* PUNIT on SPR only supports aligned 64-bit read */
@@ -96,7 +98,7 @@ intel_pmt_read(struct file *filp, struct kobject *kobj,
 		count = entry->size - off;
 
 	count = pmt_telem_read_mmio(entry->ep->pcidev, entry->cb, entry->header.guid, buf,
-				    entry->base + off, count);
+				    entry->base, off, count);
 
 	return count;
 }

drivers/platform/x86/intel/pmt/class.h

@@ -62,7 +62,7 @@ struct intel_pmt_namespace {
 };
 
 int pmt_telem_read_mmio(struct pci_dev *pdev, struct pmt_callbacks *cb, u32 guid, void *buf,
-			void __iomem *addr, u32 count);
+			void __iomem *addr, loff_t off, u32 count);
 bool intel_pmt_is_early_client_hw(struct device *dev);
 int intel_pmt_dev_create(struct intel_pmt_entry *entry,
 			 struct intel_pmt_namespace *ns,

drivers/platform/x86/intel/pmt/telemetry.c

@@ -219,7 +219,7 @@ int pmt_telem_read(struct telem_endpoint *ep, u32 id, u64 *data, u32 count)
 	if (offset + NUM_BYTES_QWORD(count) > size)
 		return -EINVAL;
 
-	pmt_telem_read_mmio(ep->pcidev, ep->cb, ep->header.guid, data, ep->base + offset,
+	pmt_telem_read_mmio(ep->pcidev, ep->cb, ep->header.guid, data, ep->base, offset,
 			    NUM_BYTES_QWORD(count));
 
 	return ep->present ? 0 : -EPIPE;

include/linux/intel_vsec.h

@@ -74,10 +74,11 @@ enum intel_vsec_quirks {
  * @pdev:  PCI device reference for the callback's use
  * @guid:  ID of data to acccss
  * @data:  buffer for the data to be copied
+ * @off:   offset into the requested buffer
  * @count: size of buffer
  */
 struct pmt_callbacks {
-	int (*read_telem)(struct pci_dev *pdev, u32 guid, u64 *data, u32 count);
+	int (*read_telem)(struct pci_dev *pdev, u32 guid, u64 *data, loff_t off, u32 count);
 };
 
 /**