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SubjectRe: [PATCH 1/2] x86: Add Isolated Memory Regions for Quark X1000
From
On Mon, Dec 29, 2014 at 7:23 PM, Bryan O'Donoghue
<pure.logic@nexus-software.ie> wrote:
> 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 kilobyte.

1 KiB? (Check entire patchset).

>
> Quark_SecureBootPRM_330234_001.pdf section 4.5 details the concept of IMRs

Missed dot at the end of sentence.

> eSRAM flush, CPU Snoop, CPU SMM Mode, CPU non-SMM mode, PMU and VC0/VC1 can
> have individual read/write access masks applied to them for a given memory
> region in Quark X1000. Quark supports eightIMR sets.

Missed space.

> 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 agrees 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.
>
> Signed-off-by: Bryan O'Donoghue <pure.logic@nexus-software.ie>
> ---
> arch/x86/Kconfig | 23 ++
> arch/x86/include/asm/imr.h | 79 ++++++
> arch/x86/include/asm/intel-quark.h | 31 +++
> arch/x86/kernel/Makefile | 1 +
> arch/x86/kernel/imr.c | 529 +++++++++++++++++++++++++++++++++++++
> 5 files changed, 663 insertions(+)
> create mode 100644 arch/x86/include/asm/imr.h
> create mode 100644 arch/x86/include/asm/intel-quark.h
> create mode 100644 arch/x86/kernel/imr.c
>
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index ba397bd..8303ca2 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -526,6 +526,29 @@ config IOSF_MBI_DEBUG
>
> If you don't require the option or are in doubt, say N.
>
> +config IMR
> + tristate "Isolated Memory Region support"
> + default m
> + depends on IOSF_MBI
> + ---help---
> + This option enables support for 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 1k

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
> + - SMM mode
> + - Non SMM mode
> + - PCI VC0/VC1
> + - CPU snoop
> + - eSRAM flush
> + - PMU access
> + Quark contains a set of IMR registers and makes use of those
> + registers during it's bootup process.
> +
> + If you are running on a Galileo/Quark say Y here
> +
> config X86_RDC321X
> bool "RDC R-321x SoC"
> depends on X86_32
> diff --git a/arch/x86/include/asm/imr.h b/arch/x86/include/asm/imr.h
> new file mode 100644
> index 0000000..fe8f3b8
> --- /dev/null
> +++ b/arch/x86/include/asm/imr.h
> @@ -0,0 +1,79 @@
> +/*
> + * imr.h: Isolated Memory Region API
> + *
> + * Copyright(c) 2013 Intel Corporation.
> + * Copyright(c) 2014 Bryan O'Donoghue <pure.logic@nexus-software.ie>

2015 everywhere I guess.

> + *
> + * 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 <asm/intel-quark.h>
> +#include <linux/types.h>
> +
> +/*
> + * Right now IMRs are not reported via CPUID though it'd be really great if
> + * future silicon did report via CPUID for this feature bringing it in-line with
> + * other similar features - like MTRRs, MSRs etc.
> + *
> + * A macro is defined here which is an analog to the other cpu_has_x type
> + * features
> + */
> +#define cpu_has_imr cpu_is_quark
> +
> +/* IMR agent access mask bits */
> +#define IMR_ESRAM_FLUSH 0x80000000
> +#define IMR_CPU_SNOOP 0x40000000
> +#define IMR_HB_ACCESS 0x20000000
> +#define IMR_VC1_ID3 0x00008000
> +#define IMR_VC1_ID2 0x00004000
> +#define IMR_VC1_ID1 0x00002000
> +#define IMR_VC1_ID0 0x00001000
> +#define IMR_VC0_ID3 0x00000800
> +#define IMR_VC0_ID2 0x00000400
> +#define IMR_VC0_ID1 0x00000200
> +#define IMR_VC0_ID0 0x00000100
> +#define IMR_SMM 0x00000002
> +#define IMR_NON_SMM 0x00000001
> +#define IMR_ACCESS_NONE 0x00000000

Can it be defined via BIT(x)?

> +
> +/* Definition of read/write masks from published BSP code */
> +#define IMR_READ_ACCESS_ALL 0xBFFFFFFF
> +#define IMR_WRITE_ACCESS_ALL 0xFFFFFFFF
> +
> +/* Number of IMRs provided by Quark X1000 SoC */
> +#define QUARK_X1000_IMR_NUM 0x07
> +#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)
> +
> +/**
> + * imr_add_range - Add an Isolated Memory Region
> + * @base: Physical base address of region aligned to 4k
> + * @size: Physical size of region in bytes
> + * @read_mask: Read access mask
> + * @write_mask: Write access mask
> + * @lock: Indicates whether or not to permenantly lock this region

It would be nice to indent descriptions after colon and use small
letter at the beginning. (Check entire patchset)

> + * @return: Index of the IMR allocated or negative value indicating error

Usually it goes as a separate section called Return like:

* Return:
* foo if A, otherwise bar.

> + */

Entire comment block should be in *.c file only.

> +int imr_add(unsigned long base, unsigned long size,

Leave _range suffix here and in the other one. It would be better I think.

> + unsigned int rmask, unsigned int wmask, bool lock);
> +
> +/**
> + * imr_del_range - Delete an Isolated Memory Region
> + * @reg: IMR index to remove
> + * @base: Physical base address of region aligned to 4k
> + * @size: Physical size of region in bytes
> + * @return: -EINVAL on invalid range or out or range id
> + * -ENODEV if reg is valid but no IMR exists or is locked
> + * 0 on success
> + */
> +int imr_del(int reg, unsigned long base, unsigned long size);

Same comments as for add_range.
Could it be imr_remove_range() ?

> +
> +#endif /* _IMR_H */
> diff --git a/arch/x86/include/asm/intel-quark.h b/arch/x86/include/asm/intel-quark.h
> new file mode 100644
> index 0000000..f51ac8c
> --- /dev/null
> +++ b/arch/x86/include/asm/intel-quark.h
> @@ -0,0 +1,31 @@
> +/*
> + * intel-quark.h: Quark shared defines and helper functions
> + *
> + * Copyright 2014 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 _ASM_X86_INTEL_QUARK_H
> +#define _ASM_X86_INTEL_QUARK_H
> +
> +#include <asm/processor.h>
> +
> +#ifdef CONFIG_X86_32
> +static inline int cpu_is_quark(const struct cpuinfo_x86 *c)
> +{
> + return (c->x86_vendor == X86_VENDOR_INTEL &&
> + c->x86 == 5 && c->x86_model == 9);
> +}
> +#else
> +static inline int cpu_is_quark(const struct cpuinfo_x86 *c)
> +{
> + return 0;
> +}
> +#endif
> +
> +#endif /* _ASM_X86_INTEL_QUARK_H */

Could we use x86_match_cpu() instead?

> +
> diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
> index 5d4502c..0252de5 100644
> --- a/arch/x86/kernel/Makefile
> +++ b/arch/x86/kernel/Makefile
> @@ -104,6 +104,7 @@ obj-$(CONFIG_EFI) += sysfb_efi.o
> obj-$(CONFIG_PERF_EVENTS) += perf_regs.o
> obj-$(CONFIG_TRACING) += tracepoint.o
> obj-$(CONFIG_IOSF_MBI) += iosf_mbi.o
> +obj-$(CONFIG_IMR) += imr.o
> obj-$(CONFIG_PMC_ATOM) += pmc_atom.o
>
> ###
> diff --git a/arch/x86/kernel/imr.c b/arch/x86/kernel/imr.c
> new file mode 100644
> index 0000000..4115138
> --- /dev/null
> +++ b/arch/x86/kernel/imr.c
> @@ -0,0 +1,529 @@
> +/**
> + * intel_imr.c
> + *
> + * Copyright(c) 2013 Intel Corporation.
> + * Copyright(c) 2014 Bryan O'Donoghue <pure.logic@nexus-software.ie>
> + *
> + * IMR registers define an isolated region of memory that can
> + * be masked to prohibit certain system agents from accessing memory.
> + * When a device behind a masked port performs an access - snooped or not, an
> + * IMR may optionally prevent that transaction from changing the state of memory
> + * or from getting correct data in response to the operation.
> + * Write data will be dropped and reads will return 0xFFFFFFFF, the system will
> + * reset and system BIOS will print out an error message to inform the user that
> + * an IMR has been violated.
> + * This code is based on the Linux MTRR code and refernece code from Intel's
> + * Quark BSP EFI, Linux and grub code.
> + */
> +#include <asm/intel-quark.h>
> +#include <asm/imr.h>
> +#include <asm/iosf_mbi.h>
> +#include <linux/debugfs.h>
> +#include <linux/init.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <linux/types.h>
> +
> +struct imr_device {
> + struct dentry *debugfs_dir;
> + struct mutex lock;
> + int num;
> + int used;
> + int reg_base;
> +};
> +
> +static struct imr_device imr_dev;
> +
> +/**

Just /*.

> + * Values derived from published code in Quark BSP
> + *
> + * addr_lo
> + * 31 Lock bit
> + * 30 Enable bit - not implemented on Quark X1000
> + * 29:25 Reserved
> + * 24:2 1 kilobyte aligned lo address
> + * 1:0 Reserved
> + *
> + * addr_hi
> + * 31:25 Reserved
> + * 24:2 1 kilobyte aligned hi address
> + * 1:0 Reserved
> + */
> +#define IMR_LOCK 0x80000000
> +#define IMR_ENABLE 0x04000000

Use BIT(x).

> +
> +struct imr {
> + u32 addr_lo;
> + u32 addr_hi;
> + u32 rmask;
> + u32 wmask;
> +};
> +
> +#define IMR_NUM_REGS (sizeof(struct imr)/sizeof(u32))
> +#define IMR_SHIFT 8


> +#define imr_to_phys(x) (x << IMR_SHIFT)
> +#define phys_to_imr(x) (x >> IMR_SHIFT)

x -> (x)

> +
> +/**
> + * imr_enabled
> + * Determines if an IMR is enabled based on address range
> + *
> + * @imr: Pointer to IMR descriptor
> + * @return true if IMR enabled false if disabled
> + */
> +static int imr_enabled(struct imr *imr)
> +{
> + return (imr_to_phys(imr->addr_lo) && imr_to_phys(imr->addr_hi));

No need to surround the return value by parentheses.

> +}
> +
> +/**
> + * imr_read
> + * Read an IMR at a given imr index. Requires caller to hold imr mutex

Summary.
* imr_read - read an IMR at a given index

This one goes to the Description I guess.
* Description:
* Requires caller to hold IMR device mutex.

Same for imr_write().

> + *
> + * @imr_id: IMR entry to read
> + * @imr: IMR structure representing address and access masks
> + * @return 0 on success or error code passed from mbi_iosf on failure
> + */
> +static int imr_read(u32 imr_id, struct imr *imr)
> +{
> + u32 reg = imr_dev.reg_base + (imr_id * IMR_NUM_REGS);

No need to have parentheses.
Same for _write().

> + int ret;
> +
> + ret = iosf_mbi_read(QRK_MBI_UNIT_MM, QRK_MBI_MM_READ,
> + reg, &imr->addr_lo);
> + if (ret)
> + return ret;
> +
> + ret = iosf_mbi_read(QRK_MBI_UNIT_MM, QRK_MBI_MM_READ,
> + ++reg, &imr->addr_hi);

Could you use reg++ in previous line and so on?

One more idea, if you make a union inside the structure you may do
this in a loop.
struct imr {
union {
struct imr {
...
};
u32 regs[IMR_NUM_REGS];
};
}

Mostly same for _write().

> + if (ret)
> + return ret;
> +
> + ret = iosf_mbi_read(QRK_MBI_UNIT_MM, QRK_MBI_MM_READ,
> + ++reg, &imr->rmask);
> + if (ret)
> + return ret;
> +
> + return iosf_mbi_read(QRK_MBI_UNIT_MM, QRK_MBI_MM_READ,
> + ++reg, &imr->wmask);
> +}
> +
> +/**
> + * imr_write
> + * Write an IMR at a given imr index. Requires caller to hold imr mutex
> + * Note lock bits need to be written independently of address bits
> + *
> + * @imr_id: IMR entry to write
> + * @imr: IMR structure representing address and access masks
> + * @lock: Indicates if the IMR lock bit should be applied
> + * @return 0 on success or error code passed from mbi_iosf on failure
> + */
> +static int imr_write(u32 imr_id, struct imr *imr, bool lock)
> +{
> + unsigned long flags;
> + u32 reg = imr_dev.reg_base + (imr_id * IMR_NUM_REGS);
> + u32 reg_lock = reg;

Do we need a separate variable? Would (reg - IMR_NUM_REGS) work for you?

> + int ret;
> +
> + local_irq_save(flags);
> +
> + ret = iosf_mbi_write(QRK_MBI_UNIT_MM, QRK_MBI_MM_WRITE, reg,
> + imr->addr_lo);
> + if (ret)
> + goto done;
> +
> + ret = iosf_mbi_write(QRK_MBI_UNIT_MM, QRK_MBI_MM_WRITE,
> + ++reg, imr->addr_hi);
> + if (ret)
> + goto done;
> +
> + ret = iosf_mbi_write(QRK_MBI_UNIT_MM, QRK_MBI_MM_WRITE,
> + ++reg, imr->rmask);
> + if (ret)
> + goto done;
> +
> + ret = iosf_mbi_write(QRK_MBI_UNIT_MM, QRK_MBI_MM_WRITE,
> + ++reg, imr->wmask);
> + if (ret)
> + goto done;
> +
> + /* Lock bit must be set separately to addr_lo address bits */
> + if (lock) {
> + imr->addr_lo |= IMR_LOCK;
> + ret = iosf_mbi_write(QRK_MBI_UNIT_MM, QRK_MBI_MM_WRITE,
> + reg_lock, imr->addr_lo);
> + }
> +
> +done:
> + local_irq_restore(flags);

Could you do like

local_irq_restore(flags);
return 0;
done:
local_irq_restore(flags);
WARN(...)
return ret;
?

> +
> + /*
> + * If writing to the IOSF failed then we're in an unknown state
> + * likely a very bad state. An IMR in an invalid state will almost
> + * certainly lead to a memory access violation.
> + */
> + if (ret)
> + WARN(1, "IOSF-MBI write fail range 0x%08x-0x%08x unreliable\n",
> + imr_to_phys(imr->addr_lo),
> + imr_to_phys(imr->addr_hi) + IMR_MASK);
> +
> + return ret;
> +}
> +
> +#ifdef CONFIG_DEBUG_FS
> +
> +/**
> + * imr_dbgfs_state_show
> + * Print state of IMR registers
> + *
> + * @s: pointer to seq_file for output
> + * @unused: unused parameter
> + * @return 0 on success or error code passed from mbi_iosf on failure
> + */
> +static int imr_dbgfs_state_show(struct seq_file *s, void *unused)
> +{
> + int i, ret = -ENODEV;
> + struct imr imr;
> + u32 size;
> +
> + mutex_lock(&imr_dev.lock);

It seems you may get the imr_dev via parameters. I suggest to avoid
using global variables as much as possible.

> +
> + for (i = 0; i <= imr_dev.num; i++) {

num is not num, but last one? Sounds confusing for me.

> +
> + ret = imr_read(i, &imr);
> + if (ret)
> + break;
> +
> + /*
> + * Remember to add IMR_ALIGN bytes to size to indicate the
> + * inherent IMR_ALIGN size bytes contained in the masked away
> + * lower ten bits
> + */
> + size = 0;

It might be an else branch.

> + if (imr_enabled(&imr)) {
> + size = imr_to_phys(imr.addr_hi) -
> + imr_to_phys(imr.addr_lo);

Could it be one line?

> + size += IMR_ALIGN;

Could it fit this one too?

> + }
> + seq_printf(s, "imr%02i: base=0x%08x, end=0x%08x, size=0x%08x "
> + "rmask=0x%08x, wmask=0x%08x, %s, %s\n", i,
> + imr_to_phys(imr.addr_lo),
> + imr_to_phys(imr.addr_hi) + IMR_MASK, size,
> + imr.rmask, imr.wmask,
> + imr_enabled(&imr) ? "enabled " : "disabled",
> + imr.addr_lo & IMR_LOCK ? "locked" : "unlocked");
> + }
> +
> + mutex_unlock(&imr_dev.lock);
> +
> + return ret;
> +}
> +
> +/**
> + * imr_state_open
> + * Debugfs open callback
> + *
> + * @inode: pointer to struct inode
> + * @file: pointer to struct file
> + * @return result of single open
> + */
> +static int imr_state_open(struct inode *inode, struct file *file)
> +{
> + return single_open(file, imr_dbgfs_state_show, inode->i_private);
> +}
> +
> +static const struct file_operations imr_state_ops = {
> + .open = imr_state_open,
> + .read = seq_read,
> + .llseek = seq_lseek,
> + .release = single_release,
> +};
> +
> +/**
> + * imr_debugfs_register
> + * Register debugfs hooks
> + *
> + * @imr: IMR structure representing address and access masks
> + * @return 0 on success - errno on failure
> + */
> +static int imr_debugfs_register(struct imr_device *imr_dev)
> +{
> + struct dentry *dir, *f;
> +
> + dir = debugfs_create_dir("imr", NULL);
> + if (!dir)
> + return -ENOMEM;

if (IS_ERR(dir))
return PTR_ERR();

Though it seems not a case when you have this under ifdef.

> +
> + f = debugfs_create_file("state", S_IFREG | S_IRUGO,
> + dir, imr_dev, &imr_state_ops);
> + if (!f)
> + goto err;

Are you planing to extend the debugfs contents? Would it be okay to
use only one file for now?

> +
> + imr_dev->debugfs_dir = dir;
> +
> + return 0;
> +err:
> + return -ENODEV;

No need to have separate label for plain return.

> +}
> +
> +/**
> + * imr_debugfs_unregister
> + * Unregister debugfs hooks
> + *
> + * @imr: IMR structure representing address and access masks
> + * @return none
> + */
> +static void imr_debugfs_unregister(struct imr_device *imr_dev)
> +{

> + if (!imr_dev->debugfs_dir)
> + return;

Redundant check.

> +
> + debugfs_remove_recursive(imr_dev->debugfs_dir);
> + imr_dev->debugfs_dir = NULL;

No need to assign NULL.

> +}

No need to put this function under ifdef - debugfs has the stubs.
Or add ifdefs around places where they are called and remove those
dummy functions below.

> +
> +#else
> +
> +/**
> + * imr_debugfs_register
> + * Register debugfs hooks
> + *
> + * @imr: IMR structure representing address and access masks
> + * @return 0 on success - errno on failure
> + */
> +static int imr_debugfs_register(struct imr_device *imr_dev)
> +{
> + return 0;
> +}
> +
> +/**
> + * imr_debugfs_unregister
> + * Dummy hook for !CONFIG_DEBUG_FS
> + *
> + * @imr: IMR structure representing address and access masks
> + * @return none
> + */
> +static void imr_debugfs_unregister(struct imr_device *imr_dev)
> +{
> +}
> +
> +#endif /* CONFIG_DEBUG_FS */
> +
> +/**
> + * imr_check_range
> + * Check the passed address range for an IMR is aligned
> + *
> + * @base: base address of intended IMR
> + * @size: size of intended IMR
> + * @return zero on valid range -EINVAL on unaligned base/size
> + */
> +static int imr_check_range(unsigned long base, unsigned long size)
> +{
> + if ((base & (IMR_MASK)) || (size & (IMR_MASK))) {

Too many parentheses. Looks like you may do it less.

> + pr_warn("imr: base 0x%08lx size 0x%08lx must align to 1k\n",

Can you define pr_fmt() ?

1 KiB.

> + base, size);
> + dump_stack();

dump_stack is really needed here? In that case why not to use WARN()?

> + return -EINVAL;
> + }
> + return 0;
> +}
> +
> +/**
> + * imr_add_range
> + * Add an Isolated Memory Region
> + *
> + * @base: Physical base address of region aligned to 4k
> + * @size: Physical size of region in bytes
> + * @read_mask: Read access mask
> + * @write_mask: Write access mask
> + * @lock: Indicates whether or not to permenantly lock this region
> + * @return: Index of the IMR allocated or negative value indicating error
> + */
> +int imr_add(unsigned long base, unsigned long size,
> + unsigned int rmask, unsigned int wmask, bool lock)
> +{
> + unsigned long end = base + size;
> + struct imr imr;
> + int reg, i, overlap, ret;
> +
> + if (imr_check_range(base, size))
> + return -EINVAL;

ret = imr_();
if (ret)
return ret;

> +
> + if (!size) {
> + pr_warn("imr: invalid size zero!\n");
> + return -EINVAL;
> + }
> +
> + mutex_lock(&imr_dev.lock);
> +
> + /* Find an free IMR while checking for an existing overlapping range */
> + overlap = 0;
> + reg = -1;
> + for (i = 0; i <= imr_dev.num; i++) {
> + ret = imr_read(i, &imr);
> + if (ret)
> + goto done;
> +
> + /* Find overlap */
> + if (imr_enabled(&imr)) {
> + if (base >= imr_to_phys(imr.addr_lo) &&
> + base <= imr_to_phys(imr.addr_hi)) {

> + overlap = 1;
> + break;

Maybe
ret = -EINVAL;
goto done;

> + }
> + if (end >= imr_to_phys(imr.addr_lo) &&
> + end <= imr_to_phys(imr.addr_hi)) {
> + overlap = 1;
> + break;

Ditto.

> + }

You may use one condition. If you still want to have them split you
may create a helper to check for overlap.

> + } else {
> + reg = i;
> + }
> + }
> +
> + /* Error out if we have an overlap or no free IMR entries */
> + if (overlap) {
> + ret = -EINVAL;
> + goto done;
> + }

...and remove overlap variable and this condition.

> + if (reg == -1) {
> + ret = -ENODEV;
> + goto done;
> + }
> +
> + pr_debug("IMR %d phys 0x%08lx-0x%08lx rmask 0x%08x wmask 0x%08x\n",
> + reg, base, end, rmask, wmask);
> +
> + /* Allocate IMR */
> + imr.addr_lo = IMR_ENABLE | phys_to_imr(base);
> + imr.addr_hi = phys_to_imr(end);
> + imr.rmask = rmask;
> + imr.wmask = wmask;
> +
> + ret = imr_write(reg, &imr, lock);
> +
> +done:
> + mutex_unlock(&imr_dev.lock);
> + return ret;
> +}
> +EXPORT_SYMBOL(imr_add);
> +
> +/**
> + * imr_del_range
> + * Delete an Isolated Memory Region
> + *
> + * @reg: IMR index to remove
> + * @base: Physical base address of region aligned to 4k
> + * @size: Physical size of region in bytes
> + * @return: -EINVAL on invalid range or out or range id
> + * -ENODEV if reg is valid but no IMR exists or is locked
> + * 0 on success
> + */
> +int imr_del(int reg, unsigned long base, unsigned long size)
> +{
> + struct imr imr;
> + int found = 0, i, ret = 0;
> + unsigned long max = base + size;
> +
> + if (imr_check_range(base, size))
> + return -EINVAL;
> +
> + if (reg > imr_dev.num)
> + return -EINVAL;
> +
> + mutex_lock(&imr_dev.lock);
> +
> + /* if a specific IMR is given try to use it */

Use capital letter to start a comment. Check a whole code.

> + if (reg >= 0) {
> + ret = imr_read(reg, &imr);
> + if (ret)
> + goto done;
> +
> + if (!imr_enabled(&imr) || imr.addr_lo & IMR_LOCK) {
> + ret = -ENODEV;
> + goto done;
> + }
> + found = 1;

You may put a loop to the else branch instead of checking found at
each iteration.

> + }
> +
> + /* search for match based on address range */
> + for (i = 0; i <= imr_dev.num && found == 0; i++) {
> + ret = imr_read(reg, &imr);
> + if (ret)
> + goto done;
> +
> + if (!imr_enabled(&imr) || imr.addr_lo & IMR_LOCK)
> + continue;
> +
> + if ((imr_to_phys(imr.addr_lo) == base) &&
> + (imr_to_phys(imr.addr_hi) == max)) {
> + reg = i;

> + found = 1;
break;

> + }
> + }
> +
> + if (found == 0) {
> + ret = -ENODEV;
> + goto done;
> + }
> +
> + /* Tear down the IMR */
> + imr.addr_lo = 0;
> + imr.addr_hi = 0;
> + imr.rmask = IMR_READ_ACCESS_ALL;
> + imr.wmask = IMR_WRITE_ACCESS_ALL;
> +
> + ret = imr_write(reg, &imr, false);
> +
> +done:
> + mutex_unlock(&imr_dev.lock);
> + return ret;
> +}
> +EXPORT_SYMBOL(imr_del);
> +
> +/**
> + * intel_imr_probe
> + * entry point for IMR driver
> + *
> + * return: -ENODEV for no IMR support 0 if good to go
> + */
> +static int __init intel_imr_init(void)
> +{
> + struct cpuinfo_x86 *c = &cpu_data(cpu);
> +
> + if (!cpu_has_imr(c))
> + return -ENODEV;
> +
> + if (iosf_mbi_available() == false)
> + return -ENODEV;
> +
> + if (cpu_is_quark(c)) {
> + imr_dev.num = QUARK_X1000_IMR_NUM;
> + imr_dev.reg_base = QUARK_X1000_IMR_REGBASE;
> + } else {
> + pr_err("Unknown IMR implementation\n");
> + return -ENODEV;
> + }
> +
> + mutex_init(&imr_dev.lock);
> +
> + return imr_debugfs_register(&imr_dev);
> +}
> +
> +/**
> + * intel_imr_exit
> + * exit point for IMR code. Deregisters debugfs, leave IMR state as-is.
> + *
> + * return: none
> + */
> +static void __exit intel_imr_exit(void)
> +{
> + imr_debugfs_unregister(&imr_dev);
> +}
> +
> +module_init(intel_imr_init);
> +module_exit(intel_imr_exit);
> +
> +MODULE_AUTHOR("Bryan O'Donoghue <pure.logic@nexus-software.ie>");
> +MODULE_DESCRIPTION("Intel Isolated Memory Region driver");
> +MODULE_LICENSE("GPL");
> --
> 1.9.1
>
> --
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Happy New Year!

--
With Best Regards,
Andy Shevchenko


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