x86/speculation: Rework speculative_store_bypass_update()

[mirror_ubuntu-artful-kernel.git] / arch / x86 / include / asm / spec-ctrl.h

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _ASM_X86_SPECCTRL_H_
#define _ASM_X86_SPECCTRL_H_

#include <linux/thread_info.h>
#include <asm/nospec-branch.h>

/*
 * On VMENTER we must preserve whatever view of the SPEC_CTRL MSR
 * the guest has, while on VMEXIT we restore the host view. This
 * would be easier if SPEC_CTRL were architecturally maskable or
 * shadowable for guests but this is not (currently) the case.
 * Takes the guest view of SPEC_CTRL MSR as a parameter and also
 * the guest's version of VIRT_SPEC_CTRL, if emulated.
 */
extern void x86_spec_ctrl_set_guest(u64 guest_spec_ctrl,
				    u64 guest_virt_spec_ctrl);
extern void x86_spec_ctrl_restore_host(u64 guest_spec_ctrl,
				       u64 guest_virt_spec_ctrl);

/*
 * On VMEXIT we must ensure that no RSB predictions learned in the guest
 * can be followed in the host, by overwriting the RSB completely. Both
 * retpoline and IBRS mitigations for Spectre v2 need this; only on future
 * CPUs with IBRS_ATT *might* it be avoided.
 */
static inline void vmexit_fill_RSB(void)
{
#ifdef CONFIG_RETPOLINE
	alternative_input("",
			  "call __fill_rsb",
			  X86_FEATURE_RETPOLINE,
			  ASM_NO_INPUT_CLOBBER(_ASM_BX, "memory"));
#endif
}

/* AMD specific Speculative Store Bypass MSR data */
extern u64 x86_amd_ls_cfg_base;
extern u64 x86_amd_ls_cfg_ssbd_mask;

/* The Intel SPEC CTRL MSR base value cache */
extern u64 x86_spec_ctrl_base;

static inline u64 ssbd_tif_to_spec_ctrl(u64 tifn)
{
	BUILD_BUG_ON(TIF_SSBD < SPEC_CTRL_SSBD_SHIFT);
	return (tifn & _TIF_SSBD) >> (TIF_SSBD - SPEC_CTRL_SSBD_SHIFT);
}

static inline u64 ssbd_tif_to_amd_ls_cfg(u64 tifn)
{
	return (tifn & _TIF_SSBD) ? x86_amd_ls_cfg_ssbd_mask : 0ULL;
}

#ifdef CONFIG_SMP
extern void speculative_store_bypass_ht_init(void);
#else
static inline void speculative_store_bypass_ht_init(void) { }
#endif

extern void speculative_store_bypass_update(unsigned long tif);

static inline void speculative_store_bypass_update_current(void)
{
	speculative_store_bypass_update(current_thread_info()->flags);
}

#endif