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authorPaolo Bonzini <pbonzini@redhat.com>2019-11-13 15:47:06 +0100
committerPaolo Bonzini <pbonzini@redhat.com>2019-11-13 15:47:06 +0100
commit13fb59276b47db556370bba53b5b55f3849dd8c9 (patch)
treeefe502b1e3302e2e0930a96830217984e76be3b5 /arch
parent8c5bd25bf42effd194d4b0b43895c42b374e620b (diff)
downloadlinux-13fb59276b47db556370bba53b5b55f3849dd8c9.tar.bz2
kvm: x86: disable shattered huge page recovery for PREEMPT_RT.
If a huge page is recovered (and becomes no executable) while another thread is executing it, the resulting contention on mmu_lock can cause latency spikes. Disabling recovery for PREEMPT_RT kernels fixes this issue. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/kvm/mmu.c5
1 files changed, 5 insertions, 0 deletions
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index fd6012eef9c9..cf718fa23dff 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -51,7 +51,12 @@
extern bool itlb_multihit_kvm_mitigation;
static int __read_mostly nx_huge_pages = -1;
+#ifdef CONFIG_PREEMPT_RT
+/* Recovery can cause latency spikes, disable it for PREEMPT_RT. */
+static uint __read_mostly nx_huge_pages_recovery_ratio = 0;
+#else
static uint __read_mostly nx_huge_pages_recovery_ratio = 60;
+#endif
static int set_nx_huge_pages(const char *val, const struct kernel_param *kp);
static int set_nx_huge_pages_recovery_ratio(const char *val, const struct kernel_param *kp);