This is a note to let you know that I've just added the patch titled
KVM: x86: limit PIT timer frequency
to the 3.13-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
kvm-x86-limit-pit-timer-frequency.patch
and it can be found in the queue-3.13 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 9ed96e87c5748de4c2807ef17e81287c7304186c Mon Sep 17 00:00:00 2001
From: Marcelo Tosatti <[email protected]>
Date: Mon, 6 Jan 2014 12:00:02 -0200
Subject: KVM: x86: limit PIT timer frequency
From: Marcelo Tosatti <[email protected]>
commit 9ed96e87c5748de4c2807ef17e81287c7304186c upstream.
Limit PIT timer frequency similarly to the limit applied by
LAPIC timer.
Reviewed-by: Jan Kiszka <[email protected]>
Signed-off-by: Marcelo Tosatti <[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
arch/x86/kvm/i8254.c | 18 ++++++++++++++++++
arch/x86/kvm/lapic.c | 3 ---
arch/x86/kvm/x86.c | 3 +++
arch/x86/kvm/x86.h | 2 ++
4 files changed, 23 insertions(+), 3 deletions(-)
--- a/arch/x86/kvm/i8254.c
+++ b/arch/x86/kvm/i8254.c
@@ -37,6 +37,7 @@
#include "irq.h"
#include "i8254.h"
+#include "x86.h"
#ifndef CONFIG_X86_64
#define mod_64(x, y) ((x) - (y) * div64_u64(x, y))
@@ -349,6 +350,23 @@ static void create_pit_timer(struct kvm
atomic_set(&ps->pending, 0);
ps->irq_ack = 1;
+ /*
+ * Do not allow the guest to program periodic timers with small
+ * interval, since the hrtimers are not throttled by the host
+ * scheduler.
+ */
+ if (ps->is_periodic) {
+ s64 min_period = min_timer_period_us * 1000LL;
+
+ if (ps->period < min_period) {
+ pr_info_ratelimited(
+ "kvm: requested %lld ns "
+ "i8254 timer period limited to %lld ns\n",
+ ps->period, min_period);
+ ps->period = min_period;
+ }
+ }
+
hrtimer_start(&ps->timer, ktime_add_ns(ktime_get(), interval),
HRTIMER_MODE_ABS);
}
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -71,9 +71,6 @@
#define VEC_POS(v) ((v) & (32 - 1))
#define REG_POS(v) (((v) >> 5) << 4)
-static unsigned int min_timer_period_us = 500;
-module_param(min_timer_period_us, uint, S_IRUGO | S_IWUSR);
-
static inline void apic_set_reg(struct kvm_lapic *apic, int reg_off, u32 val)
{
*((u32 *) (apic->regs + reg_off)) = val;
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -94,6 +94,9 @@ EXPORT_SYMBOL_GPL(kvm_x86_ops);
static bool ignore_msrs = 0;
module_param(ignore_msrs, bool, S_IRUGO | S_IWUSR);
+unsigned int min_timer_period_us = 500;
+module_param(min_timer_period_us, uint, S_IRUGO | S_IWUSR);
+
bool kvm_has_tsc_control;
EXPORT_SYMBOL_GPL(kvm_has_tsc_control);
u32 kvm_max_guest_tsc_khz;
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -125,5 +125,7 @@ int kvm_write_guest_virt_system(struct x
#define KVM_SUPPORTED_XCR0 (XSTATE_FP | XSTATE_SSE | XSTATE_YMM)
extern u64 host_xcr0;
+extern unsigned int min_timer_period_us;
+
extern struct static_key kvm_no_apic_vcpu;
#endif
Patches currently in stable-queue which might be from [email protected] are
queue-3.13/kvm-x86-limit-pit-timer-frequency.patch
queue-3.13/x86-kvm-correctly-access-the-kvm_cpuid_features-leaf-at-0x40000101.patch
queue-3.13/x86-kvm-cache-the-base-of-the-kvm-cpuid-leaves.patch
--
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