[PATCH 2/2] remoteproc: qcom: pas: Map/unmap subsystem region before auth_and_reset

[Mukesh Ojha <mukesh.ojha@oss.qualcomm.com>]

Qualcomm remoteproc drivers such as qcom_q6v5_mss, which do not use the
Peripheral Authentication Service (PAS), always map the MBA region before
use and unmap it once the usage is complete. This behavior was introduced
to avoid issues seen in the past where speculative accesses from the
application processor to the MBA region after it was assigned to the remote
Q6 led to an XPU violation. The issue was mitigated by unmapping the region
before handing control to the remote Q6.

Currently, most Qualcomm SoCs using the PAS driver run either with a
standalone QHEE or the Gunyah hypervisor. In these environments, the
hypervisor unmaps the Q6 memory from HLOS Stage-2 and remaps it into the
Q6 Stage-2 page table. As a result, speculative accesses from HLOS cannot
reach the region even if it remains mapped in HLOS Stage-1; therefore, XPU
violations cannot occur.

However, when the same SoC runs Linux at EL2, Linux itself must perform the
unmapping to avoid such issues. It is still correct to apply this mapping/
unmapping sequence even for SoCs that run under Gunyah, so this behavior
should not be conditional.

Signed-off-by: Mukesh Ojha <mukesh.ojha@oss.qualcomm.com>
---
 drivers/remoteproc/qcom_q6v5_pas.c | 48 +++++++++++++++++++++++-------
 1 file changed, 38 insertions(+), 10 deletions(-)

diff --git a/drivers/remoteproc/qcom_q6v5_pas.c b/drivers/remoteproc/qcom_q6v5_pas.c
index 3bde37ac510c..033d618ccba9 100644
--- a/drivers/remoteproc/qcom_q6v5_pas.c
+++ b/drivers/remoteproc/qcom_q6v5_pas.c
@@ -138,6 +138,13 @@ static void qcom_pas_segment_dump(struct rproc *rproc,
 		return;
 	}
 
+	pas->mem_region = ioremap_wc(pas->mem_phys, pas->mem_size);
+	if (!pas->mem_region) {
+		dev_err(pas->dev, "unable to map memory region: %pa+%zx\n",
+			&pas->mem_phys, pas->mem_size);
+		return;
+	}
+
 	memcpy_fromio(dest, pas->mem_region + total_offset, size);
 }
 
@@ -240,9 +247,18 @@ static int qcom_pas_load(struct rproc *rproc, const struct firmware *fw)
 			return ret;
 		}
 
+		pas->dtb_mem_region = ioremap_wc(pas->dtb_mem_phys, pas->dtb_mem_size);
+		if (!pas->dtb_mem_region) {
+			dev_err(pas->dev, "unable to map dtb memory region: %pa+%zx\n",
+				&pas->dtb_mem_phys, pas->dtb_mem_size);
+			goto release_dtb_metadata;
+		}
+
 		ret = qcom_mdt_pas_load(pas->dtb_pas_ctx, pas->dtb_firmware,
 					pas->dtb_firmware_name, pas->dtb_mem_region,
 					&pas->dtb_mem_reloc);
+		iounmap(pas->dtb_mem_region);
+		pas->dtb_mem_region = NULL;
 		if (ret)
 			goto release_dtb_metadata;
 	}
@@ -320,8 +336,23 @@ static int qcom_pas_start(struct rproc *rproc)
 		}
 	}
 
+	/*
+	 * During subsystem restart, when coredump is enabled, region is mapped but
+	 * not unmapped there, NULL check to reuse the mapping if its already mapped.
+	 */
+	if (!pas->mem_region) {
+		pas->mem_region = ioremap_wc(pas->mem_phys, pas->mem_size);
+		if (!pas->mem_region) {
+			dev_err(pas->dev, "unable to map memory region: %pa+%zx\n",
+				&pas->mem_phys, pas->mem_size);
+			goto release_pas_metadata;
+		}
+	}
+
 	ret = qcom_mdt_pas_load(pas->pas_ctx, pas->firmware, rproc->firmware,
 				pas->mem_region, &pas->mem_reloc);
+	iounmap(pas->mem_region);
+	pas->mem_region = NULL;
 	if (ret)
 		goto release_pas_metadata;
 
@@ -447,6 +478,13 @@ static void *qcom_pas_da_to_va(struct rproc *rproc, u64 da, size_t len, bool *is
 	if (is_iomem)
 		*is_iomem = true;
 
+	pas->mem_region = ioremap_wc(pas->mem_phys, pas->mem_size);
+	if (!pas->mem_region) {
+		dev_err(pas->dev, "unable to map memory region: %pa+%zx\n",
+			&pas->mem_phys, pas->mem_size);
+		return NULL;
+	}
+
 	return pas->mem_region + offset;
 }
 
@@ -637,11 +675,6 @@ static int qcom_pas_alloc_memory_region(struct qcom_pas *pas)
 
 	pas->mem_phys = pas->mem_reloc = res.start;
 	pas->mem_size = resource_size(&res);
-	pas->mem_region = devm_ioremap_resource_wc(pas->dev, &res);
-	if (IS_ERR(pas->mem_region)) {
-		dev_err(pas->dev, "unable to map memory region: %pR\n", &res);
-		return PTR_ERR(pas->mem_region);
-	}
 
 	pas->pas_ctx = devm_qcom_scm_pas_context_alloc(pas->dev, pas->pas_id,
 						       pas->mem_phys, pas->mem_size);
@@ -660,11 +693,6 @@ static int qcom_pas_alloc_memory_region(struct qcom_pas *pas)
 
 	pas->dtb_mem_phys = pas->dtb_mem_reloc = res.start;
 	pas->dtb_mem_size = resource_size(&res);
-	pas->dtb_mem_region = devm_ioremap_resource_wc(pas->dev, &res);
-	if (IS_ERR(pas->dtb_mem_region)) {
-		dev_err(pas->dev, "unable to map dtb memory region: %pR\n", &res);
-		return PTR_ERR(pas->dtb_mem_region);
-	}
 
 	pas->dtb_pas_ctx = devm_qcom_scm_pas_context_alloc(pas->dev, pas->dtb_pas_id,
 							   pas->dtb_mem_phys,
-- 
2.50.1