arch/x86/lib/msr.c

Source file repositories/reference/linux-study-clean/arch/x86/lib/msr.c

File Facts

System
Linux kernel
Corpus path
arch/x86/lib/msr.c
Extension
.c
Size
2730 bytes
Lines
148
Domain
Architecture Layer
Bucket
arch/x86
Inferred role
Architecture Layer: exported/initcall integration point
Status
integration implementation candidate

Why This File Exists

CPU and platform-specific kernel glue: boot entry, traps, syscall entry, interrupts, page tables, context switch, and low-level barriers.

Dependency Surface

Detected Declarations

Annotated Snippet

// SPDX-License-Identifier: GPL-2.0
#include <linux/export.h>
#include <linux/kvm_types.h>
#include <linux/percpu.h>
#include <linux/preempt.h>
#include <asm/msr.h>
#define CREATE_TRACE_POINTS
#include <asm/msr-trace.h>

struct msr __percpu *msrs_alloc(void)
{
	struct msr __percpu *msrs = NULL;

	msrs = alloc_percpu(struct msr);
	if (!msrs) {
		pr_warn("%s: error allocating msrs\n", __func__);
		return NULL;
	}

	return msrs;
}
EXPORT_SYMBOL(msrs_alloc);

void msrs_free(struct msr __percpu *msrs)
{
	free_percpu(msrs);
}
EXPORT_SYMBOL(msrs_free);

/**
 * msr_read - Read an MSR with error handling
 * @msr: MSR to read
 * @m: value to read into
 *
 * It returns read data only on success, otherwise it doesn't change the output
 * argument @m.
 *
 * Return: %0 for success, otherwise an error code
 */
static int msr_read(u32 msr, struct msr *m)
{
	int err;
	u64 val;

	err = rdmsrq_safe(msr, &val);
	if (!err)
		m->q = val;

	return err;
}

/**
 * msr_write - Write an MSR with error handling
 *
 * @msr: MSR to write
 * @m: value to write
 *
 * Return: %0 for success, otherwise an error code
 */
static int msr_write(u32 msr, struct msr *m)
{
	return wrmsrq_safe(msr, m->q);
}

static inline int __flip_bit(u32 msr, u8 bit, bool set)
{
	struct msr m, m1;
	int err = -EINVAL;

	if (bit > 63)
		return err;

	err = msr_read(msr, &m);
	if (err)
		return err;

	m1 = m;
	if (set)
		m1.q |=  BIT_64(bit);
	else
		m1.q &= ~BIT_64(bit);

	if (m1.q == m.q)
		return 0;

	err = msr_write(msr, &m1);
	if (err)
		return err;

	return 1;

Annotation

Implementation Notes