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While running inside virtual machine, the kernel can bypass cache flushing. Changing sleep state in a virtual machine doesn't affect the host system sleep state and cannot lead to data loss. Before entering sleep states, the ACPI code flushes caches to prevent data loss using the WBINVD instruction. This mechanism is required on bare metal. But, any use WBINVD inside of a guest is worthless. Changing sleep state in a virtual machine doesn't affect the host system sleep state and cannot lead to data loss, so most hypervisors simply ignore it. Despite this, the ACPI code calls WBINVD unconditionally anyway. It's useless, but also normally harmless. In TDX guests, though, WBINVD stops being harmless; it triggers a virtualization exception (#VE). If the ACPI cache-flushing WBINVD were left in place, TDX guests would need handling to recover from the exception. Avoid using WBINVD whenever running under a hypervisor. This both removes the useless WBINVDs and saves TDX from implementing WBINVD handling. Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com> Reviewed-by: Dan Williams <dan.j.williams@intel.com> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lkml.kernel.org/r/20220405232939.73860-30-kirill.shutemov@linux.intel.com
54 lines
1.4 KiB
C
54 lines
1.4 KiB
C
/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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* X86 specific ACPICA environments and implementation
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*
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* Copyright (C) 2014, Intel Corporation
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* Author: Lv Zheng <lv.zheng@intel.com>
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*/
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#ifndef _ASM_X86_ACENV_H
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#define _ASM_X86_ACENV_H
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#include <asm/special_insns.h>
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/* Asm macros */
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/*
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* ACPI_FLUSH_CPU_CACHE() flushes caches on entering sleep states.
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* It is required to prevent data loss.
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*
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* While running inside virtual machine, the kernel can bypass cache flushing.
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* Changing sleep state in a virtual machine doesn't affect the host system
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* sleep state and cannot lead to data loss.
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*/
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#define ACPI_FLUSH_CPU_CACHE() \
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do { \
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if (!cpu_feature_enabled(X86_FEATURE_HYPERVISOR)) \
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wbinvd(); \
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} while (0)
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int __acpi_acquire_global_lock(unsigned int *lock);
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int __acpi_release_global_lock(unsigned int *lock);
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#define ACPI_ACQUIRE_GLOBAL_LOCK(facs, Acq) \
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((Acq) = __acpi_acquire_global_lock(&facs->global_lock))
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#define ACPI_RELEASE_GLOBAL_LOCK(facs, Acq) \
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((Acq) = __acpi_release_global_lock(&facs->global_lock))
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/*
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* Math helper asm macros
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*/
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#define ACPI_DIV_64_BY_32(n_hi, n_lo, d32, q32, r32) \
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asm("divl %2;" \
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: "=a"(q32), "=d"(r32) \
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: "r"(d32), \
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"0"(n_lo), "1"(n_hi))
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#define ACPI_SHIFT_RIGHT_64(n_hi, n_lo) \
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asm("shrl $1,%2 ;" \
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"rcrl $1,%3;" \
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: "=r"(n_hi), "=r"(n_lo) \
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: "0"(n_hi), "1"(n_lo))
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#endif /* _ASM_X86_ACENV_H */
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