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[3.8.y.z,extended,stable] Patch "KVM: x86: limit PIT timer frequency" has been added to staging queue

Message ID 1391809027-18125-1-git-send-email-kamal@canonical.com
State New
Headers show

Commit Message

Kamal Mostafa Feb. 7, 2014, 9:37 p.m. UTC 
This is a note to let you know that I have just added a patch titled

    KVM: x86: limit PIT timer frequency

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue

This patch is scheduled to be released in version 3.8.13.18.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

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From 9e2345178e9d157d5c838dcd08ed99a5e164d5e3 Mon Sep 17 00:00:00 2001
From: Marcelo Tosatti <mtosatti@redhat.com>
Date: Mon, 6 Jan 2014 12:00:02 -0200
Subject: KVM: x86: limit PIT timer frequency

commit 9ed96e87c5748de4c2807ef17e81287c7304186c upstream.

Limit PIT timer frequency similarly to the limit applied by
LAPIC timer.

Reviewed-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
 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(-)

--
1.8.3.2
diff mbox

Patch

diff --git a/arch/x86/kvm/i8254.c b/arch/x86/kvm/i8254.c
index 11300d2..98b511d 100644
--- 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))
@@ -350,6 +351,23 @@  static void create_pit_timer(struct kvm *kvm, u32 val, int is_period)
 	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);
 }
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 8da302f..6e27290 100644
--- 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;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index c22ab85..bf8c370 100644
--- 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;
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index e224f7a..3186542 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -124,5 +124,7 @@  int kvm_write_guest_virt_system(struct x86_emulate_ctxt *ctxt,

 extern u64 host_xcr0;

+extern unsigned int min_timer_period_us;
+
 extern struct static_key kvm_no_apic_vcpu;
 #endif