summaryrefslogtreecommitdiffstats
path: root/debian/patches-rt/0277-powerpc-kvm-Disable-in-kernel-MPIC-emulation-for-PRE.patch
diff options
context:
space:
mode:
Diffstat (limited to '')
-rw-r--r--debian/patches-rt/0277-powerpc-kvm-Disable-in-kernel-MPIC-emulation-for-PRE.patch45
1 files changed, 45 insertions, 0 deletions
diff --git a/debian/patches-rt/0277-powerpc-kvm-Disable-in-kernel-MPIC-emulation-for-PRE.patch b/debian/patches-rt/0277-powerpc-kvm-Disable-in-kernel-MPIC-emulation-for-PRE.patch
new file mode 100644
index 000000000..1d465fba1
--- /dev/null
+++ b/debian/patches-rt/0277-powerpc-kvm-Disable-in-kernel-MPIC-emulation-for-PRE.patch
@@ -0,0 +1,45 @@
+From f6ff6354df6d4609ce786969f2fd16afeaf88fba Mon Sep 17 00:00:00 2001
+From: Bogdan Purcareata <bogdan.purcareata@freescale.com>
+Date: Fri, 24 Apr 2015 15:53:13 +0000
+Subject: [PATCH 277/323] powerpc/kvm: Disable in-kernel MPIC emulation for
+ PREEMPT_RT
+Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.10/older/patches-5.10.204-rt100.tar.xz
+
+While converting the openpic emulation code to use a raw_spinlock_t enables
+guests to run on RT, there's still a performance issue. For interrupts sent in
+directed delivery mode with a multiple CPU mask, the emulated openpic will loop
+through all of the VCPUs, and for each VCPUs, it call IRQ_check, which will loop
+through all the pending interrupts for that VCPU. This is done while holding the
+raw_lock, meaning that in all this time the interrupts and preemption are
+disabled on the host Linux. A malicious user app can max both these number and
+cause a DoS.
+
+This temporary fix is sent for two reasons. First is so that users who want to
+use the in-kernel MPIC emulation are aware of the potential latencies, thus
+making sure that the hardware MPIC and their usage scenario does not involve
+interrupts sent in directed delivery mode, and the number of possible pending
+interrupts is kept small. Secondly, this should incentivize the development of a
+proper openpic emulation that would be better suited for RT.
+
+Acked-by: Scott Wood <scottwood@freescale.com>
+Signed-off-by: Bogdan Purcareata <bogdan.purcareata@freescale.com>
+Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
+---
+ arch/powerpc/kvm/Kconfig | 1 +
+ 1 file changed, 1 insertion(+)
+
+diff --git a/arch/powerpc/kvm/Kconfig b/arch/powerpc/kvm/Kconfig
+index 549591d9aaa2..efb5bfe93f70 100644
+--- a/arch/powerpc/kvm/Kconfig
++++ b/arch/powerpc/kvm/Kconfig
+@@ -178,6 +178,7 @@ config KVM_E500MC
+ config KVM_MPIC
+ bool "KVM in-kernel MPIC emulation"
+ depends on KVM && E500
++ depends on !PREEMPT_RT
+ select HAVE_KVM_IRQCHIP
+ select HAVE_KVM_IRQFD
+ select HAVE_KVM_IRQ_ROUTING
+--
+2.43.0
+