x86/intel/quark: Add Isolated Memory Regions for Quark X1000

Intel's Quark X1000 SoC contains a set of registers called
Isolated Memory Regions. IMRs are accessed over the IOSF mailbox
interface. IMRs are areas carved out of memory that define
read/write access rights to the various system agents within the
Quark system. For a given agent in the system it is possible to
specify if that agent may read or write an area of memory
defined by an IMR with a granularity of 1 KiB.

Quark_SecureBootPRM_330234_001.pdf section 4.5 details the
concept of IMRs quark-x1000-datasheet.pdf section 12.7.4 details
the implementation of IMRs in silicon.

eSRAM flush, CPU Snoop write-only, CPU SMM Mode, CPU non-SMM
mode, RMU and PCIe Virtual Channels (VC0 and VC1) can have
individual read/write access masks applied to them for a given
memory region in Quark X1000. This enables IMRs to treat each
memory transaction type listed above on an individual basis and
to filter appropriately based on the IMR access mask for the
memory region. Quark supports eight IMRs.

Since all of the DMA capable SoC components in the X1000 are
mapped to VC0 it is possible to define sections of memory as
invalid for DMA write operations originating from Ethernet, USB,
SD and any other DMA capable south-cluster component on VC0.
Similarly it is possible to mark kernel memory as non-SMM mode
read/write only or to mark BIOS runtime memory as SMM mode
accessible only depending on the particular memory footprint on
a given system.

On an IMR violation Quark SoC X1000 systems are configured to
reset the system, so ensuring that the IMR memory map is
consistent with the EFI provided memory map is critical to
ensure no IMR violations reset the system.

The API for accessing IMRs is based on MTRR code but doesn't
provide a /proc or /sys interface to manipulate IMRs. Defining
the size and extent of IMRs is exclusively the domain of
in-kernel code.

Quark firmware sets up a series of locked IMRs around pieces of
memory that firmware owns such as ACPI runtime data. During boot
a series of unlocked IMRs are placed around items in memory to
guarantee no DMA modification of those items can take place.
Grub also places an unlocked IMR around the kernel boot params
data structure and compressed kernel image. It is necessary for
the kernel to tear down all unlocked IMRs in order to ensure
that the kernel's view of memory passed via the EFI memory map
is consistent with the IMR memory map. Without tearing down all
unlocked IMRs on boot transitory IMRs such as those used to
protect the compressed kernel image will cause IMR violations and system reboots.

The IMR init code tears down all unlocked IMRs and sets a
protective IMR around the kernel .text and .rodata as one
contiguous block. This sanitizes the IMR memory map with respect
to the EFI memory map and protects the read-only portions of the
kernel from unwarranted DMA access.
Tested-by: Ong, Boon Leong <boon.leong.ong@intel.com>
Signed-off-by: Bryan O'Donoghue <pure.logic@nexus-software.ie>
Reviewed-by: Andy Shevchenko <andy.schevchenko@gmail.com>
Reviewed-by: Darren Hart <dvhart@linux.intel.com>
Reviewed-by: Ong, Boon Leong <boon.leong.ong@intel.com>
Cc: andy.shevchenko@gmail.com
Cc: dvhart@infradead.org
Link: http://lkml.kernel.org/r/1422635379-12476-2-git-send-email-pure.logic@nexus-software.ieSigned-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/Kconfig.debug

@@ -313,6 +313,19 @@ config DEBUG_NMI_SELFTEST
 
 	  If unsure, say N.
 
+config DEBUG_IMR_SELFTEST
+	bool "Isolated Memory Region self test"
+	default n
+	depends on INTEL_IMR
+	---help---
+	  This option enables automated sanity testing of the IMR code.
+	  Some simple tests are run to verify IMR bounds checking, alignment
+	  and overlapping. This option is really only useful if you are
+	  debugging an IMR memory map or are modifying the IMR code and want to
+	  test your changes.
+
+	  If unsure say N here.
+
 config X86_DEBUG_STATIC_CPU_HAS
 	bool "Debug alternatives"
 	depends on DEBUG_KERNEL

arch/x86/include/asm/imr.h

+/*
+ * imr.h: Isolated Memory Region API
+ *
+ * Copyright(c) 2013 Intel Corporation.
+ * Copyright(c) 2015 Bryan O'Donoghue <pure.logic@nexus-software.ie>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; version 2
+ * of the License.
+ */
+#ifndef _IMR_H
+#define _IMR_H
+
+#include <linux/types.h>
+
+/*
+ * IMR agent access mask bits
+ * See section 12.7.4.7 from quark-x1000-datasheet.pdf for register
+ * definitions.
+ */
+#define IMR_ESRAM_FLUSH		BIT(31)
+#define IMR_CPU_SNOOP		BIT(30)		/* Applicable only to write */
+#define IMR_RMU			BIT(29)
+#define IMR_VC1_SAI_ID3		BIT(15)
+#define IMR_VC1_SAI_ID2		BIT(14)
+#define IMR_VC1_SAI_ID1		BIT(13)
+#define IMR_VC1_SAI_ID0		BIT(12)
+#define IMR_VC0_SAI_ID3		BIT(11)
+#define IMR_VC0_SAI_ID2		BIT(10)
+#define IMR_VC0_SAI_ID1		BIT(9)
+#define IMR_VC0_SAI_ID0		BIT(8)
+#define IMR_CPU_0		BIT(1)		/* SMM mode */
+#define IMR_CPU			BIT(0)		/* Non SMM mode */
+#define IMR_ACCESS_NONE		0
+
+/*
+ * Read/Write access-all bits here include some reserved bits
+ * These are the values firmware uses and are accepted by hardware.
+ * The kernel defines read/write access-all in the same way as firmware
+ * in order to have a consistent and crisp definition across firmware,
+ * bootloader and kernel.
+ */
+#define IMR_READ_ACCESS_ALL	0xBFFFFFFF
+#define IMR_WRITE_ACCESS_ALL	0xFFFFFFFF
+
+/* Number of IMRs provided by Quark X1000 SoC */
+#define QUARK_X1000_IMR_MAX	0x08
+#define QUARK_X1000_IMR_REGBASE 0x40
+
+/* IMR alignment bits - only bits 31:10 are checked for IMR validity */
+#define IMR_ALIGN		0x400
+#define IMR_MASK		(IMR_ALIGN - 1)
+
+int imr_add_range(phys_addr_t base, size_t size,
+		  unsigned int rmask, unsigned int wmask, bool lock);
+
+int imr_remove_range(phys_addr_t base, size_t size);
+
+#endif /* _IMR_H */

arch/x86/platform/intel-quark/Makefile

+obj-$(CONFIG_INTEL_IMR) += imr.o
+obj-$(CONFIG_DEBUG_IMR_SELFTEST) += imr_selftest.o

arch/x86/platform/intel-quark/imr_selftest.c

+/**
+ * imr_selftest.c
+ *
+ * Copyright(c) 2013 Intel Corporation.
+ * Copyright(c) 2015 Bryan O'Donoghue <pure.logic@nexus-software.ie>
+ *
+ * IMR self test. The purpose of this module is to run a set of tests on the
+ * IMR API to validate it's sanity. We check for overlapping, reserved
+ * addresses and setup/teardown sanity.
+ *
+ */
+
+#include <asm-generic/sections.h>
+#include <asm/imr.h>
+#include <linux/init.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/types.h>
+
+#define SELFTEST KBUILD_MODNAME ": "
+/**
+ * imr_self_test_result - Print result string for self test.
+ *
+ * @res:	result code - true if test passed false otherwise.
+ * @fmt:	format string.
+ * ...		variadic argument list.
+ */
+static void __init imr_self_test_result(int res, const char *fmt, ...)
+{
+	va_list vlist;
+
+	/* Print pass/fail. */
+	if (res)
+		pr_info(SELFTEST "pass ");
+	else
+		pr_info(SELFTEST "fail ");
+
+	/* Print variable string. */
+	va_start(vlist, fmt);
+	vprintk(fmt, vlist);
+	va_end(vlist);
+
+	/* Optional warning. */
+	WARN(res == 0, "test failed");
+}
+#undef SELFTEST
+
+/**
+ * imr_self_test
+ *
+ * Verify IMR self_test with some simple tests to verify overlap,
+ * zero sized allocations and 1 KiB sized areas.
+ *
+ */
+static void __init imr_self_test(void)
+{
+	phys_addr_t base  = virt_to_phys(&_text);
+	size_t size = virt_to_phys(&__end_rodata) - base;
+	const char *fmt_over = "overlapped IMR @ (0x%08lx - 0x%08lx)\n";
+	int ret;
+
+	/* Test zero zero. */
+	ret = imr_add_range(0, 0, 0, 0, false);
+	imr_self_test_result(ret < 0, "zero sized IMR\n");
+
+	/* Test exact overlap. */
+	ret = imr_add_range(base, size, IMR_CPU, IMR_CPU, false);
+	imr_self_test_result(ret < 0, fmt_over, __va(base), __va(base + size));
+
+	/* Test overlap with base inside of existing. */
+	base += size - IMR_ALIGN;
+	ret = imr_add_range(base, size, IMR_CPU, IMR_CPU, false);
+	imr_self_test_result(ret < 0, fmt_over, __va(base), __va(base + size));
+
+	/* Test overlap with end inside of existing. */
+	base -= size + IMR_ALIGN * 2;
+	ret = imr_add_range(base, size, IMR_CPU, IMR_CPU, false);
+	imr_self_test_result(ret < 0, fmt_over, __va(base), __va(base + size));
+
+	/* Test that a 1 KiB IMR @ zero with read/write all will bomb out. */
+	ret = imr_add_range(0, IMR_ALIGN, IMR_READ_ACCESS_ALL,
+			    IMR_WRITE_ACCESS_ALL, false);
+	imr_self_test_result(ret < 0, "1KiB IMR @ 0x00000000 - access-all\n");
+
+	/* Test that a 1 KiB IMR @ zero with CPU only will work. */
+	ret = imr_add_range(0, IMR_ALIGN, IMR_CPU, IMR_CPU, false);
+	imr_self_test_result(ret >= 0, "1KiB IMR @ 0x00000000 - cpu-access\n");
+	if (ret >= 0) {
+		ret = imr_remove_range(0, IMR_ALIGN);
+		imr_self_test_result(ret == 0, "teardown - cpu-access\n");
+	}
+
+	/* Test 2 KiB works. */
+	size = IMR_ALIGN * 2;
+	ret = imr_add_range(0, size, IMR_READ_ACCESS_ALL,
+			    IMR_WRITE_ACCESS_ALL, false);
+	imr_self_test_result(ret >= 0, "2KiB IMR @ 0x00000000\n");
+	if (ret >= 0) {
+		ret = imr_remove_range(0, size);
+		imr_self_test_result(ret == 0, "teardown 2KiB\n");
+	}
+}
+
+/**
+ * imr_self_test_init - entry point for IMR driver.
+ *
+ * return: -ENODEV for no IMR support 0 if good to go.
+ */
+static int __init imr_self_test_init(void)
+{
+	imr_self_test();
+	return 0;
+}
+
+/**
+ * imr_self_test_exit - exit point for IMR code.
+ *
+ * return:
+ */
+static void __exit imr_self_test_exit(void)
+{
+}
+
+module_init(imr_self_test_init);
+module_exit(imr_self_test_exit);
+
+MODULE_AUTHOR("Bryan O'Donoghue <pure.logic@nexus-software.ie>");
+MODULE_DESCRIPTION("Intel Isolated Memory Region self-test driver");
+MODULE_LICENSE("Dual BSD/GPL");

drivers/platform/x86/Kconfig

@@ -735,6 +735,31 @@ config INTEL_IPS
 	  functionality.  If in doubt, say Y here; it will only load on
 	  supported platforms.
 
+config INTEL_IMR
+	bool "Intel Isolated Memory Region support"
+	default n
+	depends on X86_INTEL_QUARK && IOSF_MBI
+	---help---
+	  This option provides a means to manipulate Isolated Memory Regions.
+	  IMRs are a set of registers that define read and write access masks
+	  to prohibit certain system agents from accessing memory with 1 KiB
+	  granularity.
+
+	  IMRs make it possible to control read/write access to an address
+	  by hardware agents inside the SoC. Read and write masks can be
+	  defined for:
+		- eSRAM flush
+		- Dirty CPU snoop (write only)
+		- RMU access
+		- PCI Virtual Channel 0/Virtual Channel 1
+		- SMM mode
+		- Non SMM mode
+
+	  Quark contains a set of eight IMR registers and makes use of those
+	  registers during its bootup process.
+
+	  If you are running on a Galileo/Quark say Y here.
+
 config IBM_RTL
 	tristate "Device driver to enable PRTL support"
 	depends on X86 && PCI