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Message-Id: <1573656439-16252-1-git-send-email-pbonzini@redhat.com> Date: Wed, 13 Nov 2019 15:47:19 +0100 From: Paolo Bonzini <pbonzini@...hat.com> To: linux-kernel@...r.kernel.org, kvm@...r.kernel.org Subject: [PATCH] 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@...hat.com> --- arch/x86/kvm/mmu.c | 5 +++++ 1 file changed, 5 insertions(+) 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); -- 1.8.3.1
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