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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>
This commit is contained in:
Paolo Bonzini 2019-11-13 15:47:06 +01:00
parent 8c5bd25bf4
commit 13fb59276b
1 changed files with 5 additions and 0 deletions
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5
arch/x86/kvm/mmu.c
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@ -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);