diff options
| author | Michael S. Tsirkin <mst@redhat.com> | 2018-03-30 18:20:32 +0300 |
|---|---|---|
| committer | Michael S. Tsirkin <mst@redhat.com> | 2018-04-25 20:41:34 +0300 |
| commit | cfcde40e8ce3aab6f61b4998945ab19985ea852c (patch) | |
| tree | 65fba2a0a9fb2deaa8a11ef77b88c1568d6a5e4f /drivers/acpi | |
| parent | c9cb15cc51229c63ca587bd31d57865c3dbd6173 (diff) | |
ACPI: disable extra P_LVLx access on KVM
As documented by commit b488f021 "ACPI: restore comment justifying
'extra' P_LVLx access", Linux does an extra IO read after entering idle
because on (some) chipsets STPCLK# doesn't get asserted in time
to prevent further instruction processing.
This can never be the case on KVM, and a timer read causes an expensive
VM exit in turn causing useless load on host system. Detect KVM and skip
the read. TODO: whitelist more hypervisors?
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: kvm@vger.kernel.org
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Diffstat (limited to 'drivers/acpi')
| -rw-r--r-- | drivers/acpi/processor_idle.c | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c index abb559cd28d7..8ae28dc0b784 100644 --- a/drivers/acpi/processor_idle.c +++ b/drivers/acpi/processor_idle.c @@ -33,6 +33,7 @@ #include <linux/cpuidle.h> #include <linux/cpu.h> #include <acpi/processor.h> +#include <linux/kvm_para.h> /* * Include the apic definitions for x86 to have the APIC timer related defines @@ -665,7 +666,8 @@ static void __cpuidle acpi_idle_do_entry(struct acpi_processor_cx *cx) /* Dummy wait op - must do something useless after P_LVL2 read because chipsets cannot guarantee that STPCLK# signal gets asserted in time to freeze execution properly. */ - inl(acpi_gbl_FADT.xpm_timer_block.address); + if (!kvm_para_available()) + inl(acpi_gbl_FADT.xpm_timer_block.address); } } @@ -687,7 +689,8 @@ static int acpi_idle_play_dead(struct cpuidle_device *dev, int index) else if (cx->entry_method == ACPI_CSTATE_SYSTEMIO) { inb(cx->address); /* See comment in acpi_idle_do_entry() */ - inl(acpi_gbl_FADT.xpm_timer_block.address); + if (!kvm_para_available()) + inl(acpi_gbl_FADT.xpm_timer_block.address); } else return -ENODEV; } |