From 4b0590415d20a068d612507f51f69fce22f09a4e Mon Sep 17 00:00:00 2001
From: Yonghua Huang <yonghua.huang@intel.com>
Date: Tue, 8 Feb 2022 14:45:20 +0300
Subject: [PATCH] dm: disable TCC strict CPU affinity check

 By default, pCPU is allowed to request software SRAM buffer
 from given region in TCC buffer driver only if this pCPU is
 set in the target region's CPU affinity configuration.

 This check shall be disabled for software SRAM virtualization
 usage in ACRN service VM, because software SRAM buffers are
 requested by ACRN DM on behalf of user VM, but ACRN DM and
 user VM may run on different CPUs while the target software
 SRAM region may be configured only for pCPUs that user VM runs on.

 This patch turns off such affinity check in TCC driver when
 initializing vSSRAM for user VM.

Tracked-On: #7010
Signed-off-by: Yonghua Huang <yonghua.huang@intel.com>
Reviewed-by: Geoffroy Van Cutsem <geoffroy.vancutsem@intel.com>
Acked-by: Yu Wang <yu1.wang@intel.com>
---
 devicemodel/hw/platform/vssram/vssram.c | 46 +++++++++++++++++++++++++
 1 file changed, 46 insertions(+)

diff --git a/devicemodel/hw/platform/vssram/vssram.c b/devicemodel/hw/platform/vssram/vssram.c
index 74d857e66..ae50aa1d0 100644
--- a/devicemodel/hw/platform/vssram/vssram.c
+++ b/devicemodel/hw/platform/vssram/vssram.c
@@ -235,6 +235,38 @@ static int tcc_driver_init_buffer_fd(void)
 	return 0;
 }
 
+/**
+ * @brief  Disable CPU affinity check in TCC driver.
+ *
+ * @param void.
+ *
+ * @return 0 on success and -1 on fail.
+ */
+static int disable_tcc_strict_affinity_check(void)
+{
+#define AFFINITY_CHECK_PARAM "/sys/module/tcc_buffer/parameters/strict_affinity_check"
+	int fd, ret = 0U;
+
+	fd = open(AFFINITY_CHECK_PARAM, O_WRONLY);
+	if (fd < 0) {
+		pr_err("%s: Failed to open %s: %s(%i), please check its availability.\n",
+			__func__, AFFINITY_CHECK_PARAM, strerror(errno), errno);
+		return -1;
+	}
+
+	/* Value of 0 means turning off CPU affinity check. */
+	if (write(fd, "0", 1) < 0) {
+		pr_err("%s: Failed to turn off affinity checking in the TCC driver"
+			"(could not write to: %s: %s(%i)", __func__,
+			AFFINITY_CHECK_PARAM, strerror(errno), errno);
+		ret = -1;
+	}
+
+	close(fd);
+	return ret;
+}
+
+
 /**
  * @brief  Get count of TCC software SRAM regions.
  *
@@ -1232,6 +1264,20 @@ int init_vssram(struct vmctx *ctx)
 	if (tcc_driver_init_buffer_fd() < 0)
 		return -1;
 
+	/*
+	 * By default, pCPU is allowed to request software SRAM buffer
+	 * from given region in TCC buffer driver only if this pCPU is
+	 * set in the target region's CPU affinity configuration.
+	 *
+	 * This check shall be disabled for software SRAM virtualization
+	 * usage in ACRN service VM, because software SRAM buffers are
+	 * requested by ACRN DM on behalf of user VM, but ACRN DM and
+	 * user VM may run on different CPUs while the target software
+	 * SRAM region may be configured only for pCPUs that user VM runs on.
+	 */
+	if (disable_tcc_strict_affinity_check() < 0)
+		return -1;
+
 	if (vssram_init_buffers() < 0) {
 		pr_err("%s, initialize vssram buffer description failed.\n", __func__);
 		return -1;