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On an (even slightly) oversubscribed system, spinlocks are quickly becoming a bottleneck, as some vcpus are spinning, waiting for a lock to be released, while the vcpu holding the lock may not be running at all. The solution is to trap blocking WFEs and tell KVM that we're now spinning. This ensures that other vpus will get a scheduling boost, allowing the lock to be released more quickly. Also, using CONFIG_HAVE_KVM_CPU_RELAX_INTERCEPT slightly improves the performance when the VM is severely overcommited. Acked-by: Christoffer Dall <christoffer.dall@linaro.org> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
133 lines
3.6 KiB
C
133 lines
3.6 KiB
C
/*
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* Copyright (C) 2012,2013 - ARM Ltd
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* Author: Marc Zyngier <marc.zyngier@arm.com>
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*
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* Derived from arch/arm/kvm/handle_exit.c:
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* Copyright (C) 2012 - Virtual Open Systems and Columbia University
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* Author: Christoffer Dall <c.dall@virtualopensystems.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <linux/kvm.h>
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#include <linux/kvm_host.h>
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#include <asm/kvm_emulate.h>
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#include <asm/kvm_coproc.h>
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#include <asm/kvm_mmu.h>
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#include <asm/kvm_psci.h>
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typedef int (*exit_handle_fn)(struct kvm_vcpu *, struct kvm_run *);
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static int handle_hvc(struct kvm_vcpu *vcpu, struct kvm_run *run)
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{
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if (kvm_psci_call(vcpu))
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return 1;
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kvm_inject_undefined(vcpu);
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return 1;
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}
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static int handle_smc(struct kvm_vcpu *vcpu, struct kvm_run *run)
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{
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if (kvm_psci_call(vcpu))
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return 1;
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kvm_inject_undefined(vcpu);
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return 1;
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}
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/**
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* kvm_handle_wfx - handle a wait-for-interrupts or wait-for-event
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* instruction executed by a guest
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*
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* @vcpu: the vcpu pointer
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*
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* WFE: Yield the CPU and come back to this vcpu when the scheduler
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* decides to.
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* WFI: Simply call kvm_vcpu_block(), which will halt execution of
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* world-switches and schedule other host processes until there is an
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* incoming IRQ or FIQ to the VM.
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*/
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static int kvm_handle_wfx(struct kvm_vcpu *vcpu, struct kvm_run *run)
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{
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if (kvm_vcpu_get_hsr(vcpu) & ESR_EL2_EC_WFI_ISS_WFE)
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kvm_vcpu_on_spin(vcpu);
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else
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kvm_vcpu_block(vcpu);
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return 1;
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}
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static exit_handle_fn arm_exit_handlers[] = {
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[ESR_EL2_EC_WFI] = kvm_handle_wfx,
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[ESR_EL2_EC_CP15_32] = kvm_handle_cp15_32,
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[ESR_EL2_EC_CP15_64] = kvm_handle_cp15_64,
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[ESR_EL2_EC_CP14_MR] = kvm_handle_cp14_access,
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[ESR_EL2_EC_CP14_LS] = kvm_handle_cp14_load_store,
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[ESR_EL2_EC_CP14_64] = kvm_handle_cp14_access,
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[ESR_EL2_EC_HVC32] = handle_hvc,
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[ESR_EL2_EC_SMC32] = handle_smc,
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[ESR_EL2_EC_HVC64] = handle_hvc,
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[ESR_EL2_EC_SMC64] = handle_smc,
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[ESR_EL2_EC_SYS64] = kvm_handle_sys_reg,
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[ESR_EL2_EC_IABT] = kvm_handle_guest_abort,
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[ESR_EL2_EC_DABT] = kvm_handle_guest_abort,
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};
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static exit_handle_fn kvm_get_exit_handler(struct kvm_vcpu *vcpu)
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{
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u8 hsr_ec = kvm_vcpu_trap_get_class(vcpu);
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if (hsr_ec >= ARRAY_SIZE(arm_exit_handlers) ||
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!arm_exit_handlers[hsr_ec]) {
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kvm_err("Unkown exception class: hsr: %#08x\n",
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(unsigned int)kvm_vcpu_get_hsr(vcpu));
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BUG();
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}
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return arm_exit_handlers[hsr_ec];
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}
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/*
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* Return > 0 to return to guest, < 0 on error, 0 (and set exit_reason) on
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* proper exit to userspace.
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*/
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int handle_exit(struct kvm_vcpu *vcpu, struct kvm_run *run,
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int exception_index)
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{
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exit_handle_fn exit_handler;
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switch (exception_index) {
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case ARM_EXCEPTION_IRQ:
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return 1;
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case ARM_EXCEPTION_TRAP:
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/*
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* See ARM ARM B1.14.1: "Hyp traps on instructions
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* that fail their condition code check"
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*/
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if (!kvm_condition_valid(vcpu)) {
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kvm_skip_instr(vcpu, kvm_vcpu_trap_il_is32bit(vcpu));
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return 1;
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}
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exit_handler = kvm_get_exit_handler(vcpu);
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return exit_handler(vcpu, run);
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default:
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kvm_pr_unimpl("Unsupported exception type: %d",
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exception_index);
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run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
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return 0;
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}
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}
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