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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
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Based on 2 normalized pattern(s):
this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license version 2 as
published by the free software foundation
this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license version 2 as
published by the free software foundation #
extracted by the scancode license scanner the SPDX license identifier
GPL-2.0-only
has been chosen to replace the boilerplate/reference in 4122 file(s).
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Enrico Weigelt <info@metux.net>
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Allison Randal <allison@lohutok.net>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190604081206.933168790@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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The forthcoming patch will make <acpi/acpi.h> to be visible to all kernel
source code. Thus for the architectures that do not support ACPI and
haven't implemented <asm/acenv.h>, we need to make it excluded.
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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Since mis-order issues have been solved, we can cleanup redundant
definitions that already have defaults in <acpi/platform/acenv.h>.
This patch removes redudant environments for __KERNEL__ surrounded code.
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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<asm/acpi.h>
There is a mis-order inclusion for <asm/acpi.h>.
As we will enforce including <linux/acpi.h> for all Linux ACPI users, we
can find the inclusion order is as follows:
<linux/acpi.h>
<acpi/acpi.h>
<acpi/platform/acenv.h>
(acenv.h before including aclinux.h)
<acpi/platform/aclinux.h>
...........................................................................
(aclinux.h before including asm/acpi.h)
<asm/acpi.h> @Redundant@
(ACPICA specific stuff)
...........................................................................
...........................................................................
(Linux ACPI specific stuff) ? - - - - - - - - - - - - +
(aclinux.h after including asm/acpi.h) @Invisible@ |
(acenv.h after including aclinux.h) @Invisible@ |
other ACPICA headers @Invisible@ |
............................................................|..............
<acpi/acpi_bus.h> |
<acpi/acpi_drivers.h> |
<asm/acpi.h> (Excluded) |
(Linux ACPI specific stuff) ! <- - - - - - - - - - - - - +
NOTE that, in ACPICA, <acpi/platform/acenv.h> is more like Kconfig
generated <generated/autoconf.h> for Linux, it is meant to be included
before including any ACPICA code.
In the above figure, there is a question mark for "Linux ACPI specific
stuff" in <asm/acpi.h> which should be included after including all other
ACPICA header files. Thus they really need to be moved to the position
marked with exclaimation mark or the definitions in the blocks marked with
"@Invisible@" will be invisible to such architecture specific "Linux ACPI
specific stuff" header blocks. This leaves 2 issues:
1. All environmental definitions in these blocks should have a copy in the
area marked with "@Redundant@" if they are required by the "Linux ACPI
specific stuff".
2. We cannot use any ACPICA defined types in <asm/acpi.h>.
This patch splits architecture specific ACPICA stuff from <asm/acpi.h> to
fix this issue.
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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