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[PATCH 4.2.y-ckt 31/70] KVM: x86: Inject pending interrupt even if pending nmi exist

From Kamal Mostafa <kamal@canonical.com>
Newsgroups linux.kernel
Subject [PATCH 4.2.y-ckt 31/70] KVM: x86: Inject pending interrupt even if pending nmi exist
Date 2016-04-12 23:30 +0200
Message-ID <rne2M-5Op-63@gated-at.bofh.it> (permalink)
References <rndzH-5be-3@gated-at.bofh.it>
Organization linux.* mail to news gateway

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4.2.8-ckt8 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: Yuki Shibuya <shibuya.yk@ncos.nec.co.jp>

commit 321c5658c5e9192dea0d58ab67cf1791e45b2b26 upstream.

Non maskable interrupts (NMI) are preferred to interrupts in current
implementation. If a NMI is pending and NMI is blocked by the result
of nmi_allowed(), pending interrupt is not injected and
enable_irq_window() is not executed, even if interrupts injection is
allowed.

In old kernel (e.g. 2.6.32), schedule() is often called in NMI context.
In this case, interrupts are needed to execute iret that intends end
of NMI. The flag of blocking new NMI is not cleared until the guest
execute the iret, and interrupts are blocked by pending NMI. Due to
this, iret can't be invoked in the guest, and the guest is starved
until block is cleared by some events (e.g. canceling injection).

This patch injects pending interrupts, when it's allowed, even if NMI
is blocked. And, If an interrupts is pending after executing
inject_pending_event(), enable_irq_window() is executed regardless of
NMI pending counter.

Signed-off-by: Yuki Shibuya <shibuya.yk@ncos.nec.co.jp>
Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
 arch/x86/kvm/x86.c | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 9a16d3fd..382a150 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6141,12 +6141,10 @@ static int inject_pending_event(struct kvm_vcpu *vcpu, bool req_int_win)
 	}
 
 	/* try to inject new event if pending */
-	if (vcpu->arch.nmi_pending) {
-		if (kvm_x86_ops->nmi_allowed(vcpu)) {
-			--vcpu->arch.nmi_pending;
-			vcpu->arch.nmi_injected = true;
-			kvm_x86_ops->set_nmi(vcpu);
-		}
+	if (vcpu->arch.nmi_pending && kvm_x86_ops->nmi_allowed(vcpu)) {
+		--vcpu->arch.nmi_pending;
+		vcpu->arch.nmi_injected = true;
+		kvm_x86_ops->set_nmi(vcpu);
 	} else if (kvm_cpu_has_injectable_intr(vcpu)) {
 		/*
 		 * Because interrupts can be injected asynchronously, we are
@@ -6550,10 +6548,12 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
 		if (inject_pending_event(vcpu, req_int_win) != 0)
 			req_immediate_exit = true;
 		/* enable NMI/IRQ window open exits if needed */
-		else if (vcpu->arch.nmi_pending)
-			kvm_x86_ops->enable_nmi_window(vcpu);
-		else if (kvm_cpu_has_injectable_intr(vcpu) || req_int_win)
-			kvm_x86_ops->enable_irq_window(vcpu);
+		else {
+			if (vcpu->arch.nmi_pending)
+				kvm_x86_ops->enable_nmi_window(vcpu);
+			if (kvm_cpu_has_injectable_intr(vcpu) || req_int_win)
+				kvm_x86_ops->enable_irq_window(vcpu);
+		}
 
 		if (kvm_lapic_enabled(vcpu)) {
 			/*
-- 
2.7.4

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[4.2.y-ckt stable] Linux 4.2.8-ckt8 stable review Kamal Mostafa <kamal@canonical.com> - 2016-04-12 23:00 +0200
  [PATCH 4.2.y-ckt 69/70] mwifiex: fix corner case association failure Kamal Mostafa <kamal@canonical.com> - 2016-04-12 23:00 +0200
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  [PATCH 4.2.y-ckt 63/70] efi: Add pstore variables to the deletion whitelist Kamal Mostafa <kamal@canonical.com> - 2016-04-12 23:00 +0200
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  [PATCH 4.2.y-ckt 09/70] hwmon: (max1111) Return -ENODEV from max1111_read_channel if not instantiated Kamal Mostafa <kamal@canonical.com> - 2016-04-12 23:00 +0200
  [PATCH 4.2.y-ckt 70/70] net: phy: at803x: Request 'reset' GPIO only for AT8030 PHY Kamal Mostafa <kamal@canonical.com> - 2016-04-12 23:00 +0200
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  [PATCH 4.2.y-ckt 47/70] gpio: pca953x: Use correct u16 value for register word write Kamal Mostafa <kamal@canonical.com> - 2016-04-12 23:30 +0200
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  [PATCH 4.2.y-ckt 33/70] mm: fix invalid node in alloc_migrate_target() Kamal Mostafa <kamal@canonical.com> - 2016-04-12 23:30 +0200
  [PATCH 4.2.y-ckt 57/70] KVM: x86: move steal time initialization to vcpu entry time Kamal Mostafa <kamal@canonical.com> - 2016-04-12 23:30 +0200
  [PATCH 4.2.y-ckt 37/70] usb: renesas_usbhs: fix to avoid using a disabled ep in usbhsg_queue_done() Kamal Mostafa <kamal@canonical.com> - 2016-04-12 23:30 +0200
  [PATCH 4.2.y-ckt 40/70] rbd: use GFP_NOIO consistently for request allocations Kamal Mostafa <kamal@canonical.com> - 2016-04-12 23:30 +0200
  [PATCH 4.2.y-ckt 50/70] parisc: Unbreak handling exceptions from kernel modules Kamal Mostafa <kamal@canonical.com> - 2016-04-12 23:30 +0200
  [PATCH 4.2.y-ckt 52/70] net: bcmgenet: fix dev->stats.tx_bytes accounting Kamal Mostafa <kamal@canonical.com> - 2016-04-12 23:30 +0200
  [PATCH 4.2.y-ckt 31/70] KVM: x86: Inject pending interrupt even if pending nmi exist Kamal Mostafa <kamal@canonical.com> - 2016-04-12 23:30 +0200
  [PATCH 4.2.y-ckt 34/70] iio: st_magn: always define ST_MAGN_TRIGGER_SET_STATE Kamal Mostafa <kamal@canonical.com> - 2016-04-12 23:30 +0200
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  [PATCH 4.2.y-ckt 26/70] sd: Fix excessive capacity printing on devices with blocks bigger than 512 bytes Kamal Mostafa <kamal@canonical.com> - 2016-04-12 23:40 +0200
  [PATCH 4.2.y-ckt 23/70] USB: digi_acceleport: do sanity checking for the number of ports Kamal Mostafa <kamal@canonical.com> - 2016-04-12 23:40 +0200
  [PATCH 4.2.y-ckt 32/70] ALSA: timer: Use mod_timer() for rearming the system timer Kamal Mostafa <kamal@canonical.com> - 2016-04-12 23:40 +0200
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  [PATCH 4.2.y-ckt 15/70] pinctrl: sunxi: Fix A33 external interrupts not working Kamal Mostafa <kamal@canonical.com> - 2016-04-12 23:40 +0200
  [PATCH 4.2.y-ckt 28/70] drm/udl: Use unlocked gem unreferencing Kamal Mostafa <kamal@canonical.com> - 2016-04-12 23:40 +0200
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  [PATCH 4.2.y-ckt 12/70] powerpc/mm: Fixup preempt underflow with huge pages Kamal Mostafa <kamal@canonical.com> - 2016-04-12 23:40 +0200
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  [PATCH 4.2.y-ckt 18/70] btrfs: fix crash/invalid memory access on fsync when using overlayfs Kamal Mostafa <kamal@canonical.com> - 2016-04-12 23:40 +0200
  [PATCH 4.2.y-ckt 29/70] ext4: add lockdep annotations for i_data_sem Kamal Mostafa <kamal@canonical.com> - 2016-04-12 23:40 +0200
  [PATCH 4.2.y-ckt 11/70] drm/radeon: add a dpm quirk for all R7 370 parts Kamal Mostafa <kamal@canonical.com> - 2016-04-12 23:40 +0200
  [PATCH 4.2.y-ckt 13/70] pinctrl: sh-pfc: only use dummy states for non-DT platforms Kamal Mostafa <kamal@canonical.com> - 2016-04-12 23:40 +0200
  [PATCH 4.2.y-ckt 17/70] usb: renesas_usbhs: disable TX IRQ before starting TX DMAC transfer Kamal Mostafa <kamal@canonical.com> - 2016-04-12 23:40 +0200
  [PATCH 4.2.y-ckt 21/70] USB: mct_u232: add sanity checking in probe Kamal Mostafa <kamal@canonical.com> - 2016-04-12 23:40 +0200
  [PATCH 4.2.y-ckt 25/70] [media] au0828: Fix dev_state handling Kamal Mostafa <kamal@canonical.com> - 2016-04-12 23:40 +0200
  [PATCH 4.2.y-ckt 07/70] fs: add file_dentry() Kamal Mostafa <kamal@canonical.com> - 2016-04-12 23:40 +0200

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