linux-kernel - [PATCH v4 11/14] cxl/atl: Lock decoders that need address translation

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Message-ID: <20251103184804.509762-12-rrichter@amd.com>
Date: Mon, 3 Nov 2025 19:47:52 +0100
From: Robert Richter <rrichter@....com>
To: Alison Schofield <alison.schofield@...el.com>, Vishal Verma
	<vishal.l.verma@...el.com>, Ira Weiny <ira.weiny@...el.com>, Dan Williams
	<dan.j.williams@...el.com>, Jonathan Cameron <Jonathan.Cameron@...wei.com>,
	Dave Jiang <dave.jiang@...el.com>, Davidlohr Bueso <dave@...olabs.net>,
	Jonathan Cameron <jonathan.cameron@...wei.com>
CC: <linux-cxl@...r.kernel.org>, <linux-kernel@...r.kernel.org>, Gregory Price
	<gourry@...rry.net>, "Fabio M. De Francesco"
	<fabio.m.de.francesco@...ux.intel.com>, Terry Bowman <terry.bowman@....com>,
	Joshua Hahn <joshua.hahnjy@...il.com>, Robert Richter <rrichter@....com>
Subject: [PATCH v4 11/14] cxl/atl: Lock decoders that need address translation

There is only support to translate addresses from an endpoint to its
CXL host bridge, but not in the opposite direction from the bridge to
the endpoint. Thus, the endpoint address range cannot be determined
and setup manually for a given SPA range of a region. If the endpoint
has address translation enabled, lock it to prevent the kernel from
reconfiguring it.

Reviewed-by: Gregory Price <gourry@...rry.net>
Signed-off-by: Robert Richter <rrichter@....com>
---
 drivers/cxl/core/atl.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/cxl/core/atl.c b/drivers/cxl/core/atl.c
index d6aa7e6d0ac5..5c15e4d12193 100644
--- a/drivers/cxl/core/atl.c
+++ b/drivers/cxl/core/atl.c
@@ -158,6 +158,16 @@ static int cxl_prm_translate_hpa_range(struct cxl_root *cxl_root, void *data)
 		return -ENXIO;
 	}
 
+	/*
+	 * There is only support to translate from the endpoint to its
+	 * parent port, but not in the opposite direction from the
+	 * parent to the endpoint. Thus, the endpoint address range
+	 * cannot be determined and setup manually. If the address range
+	 * was translated and modified, forbid reprogramming of the
+	 * decoders and lock them.
+	 */
+	cxld->flags |= CXL_DECODER_F_LOCK;
+
 	ctx->hpa_range = hpa_range;
 	ctx->interleave_ways = ways;
 	ctx->interleave_granularity = gran;
-- 
2.47.3