From aebd3bd586c67a29ddbe7be7db06b45754477b52 Mon Sep 17 00:00:00 2001 From: Bibo Mao Date: Wed, 6 Mar 2024 09:12:13 +0800 Subject: [PATCH 1/4] LoongArch: KVM: Set reserved bits as zero in CPUCFG Supported CPUCFG information comes from function _kvm_get_cpucfg_mask(). A bit should be zero if it is reserved by HW or if it is not supported by KVM. Also LoongArch software page table walk feature defined in CPUCFG2_LSPW is supported by KVM, it should be enabled by default. Signed-off-by: Bibo Mao Signed-off-by: Huacai Chen --- arch/loongarch/kvm/vcpu.c | 33 ++++++++++++++++++++++++++------- 1 file changed, 26 insertions(+), 7 deletions(-) diff --git a/arch/loongarch/kvm/vcpu.c b/arch/loongarch/kvm/vcpu.c index 36106922b5d7..3a8779065f73 100644 --- a/arch/loongarch/kvm/vcpu.c +++ b/arch/loongarch/kvm/vcpu.c @@ -304,11 +304,18 @@ static int _kvm_get_cpucfg_mask(int id, u64 *v) return -EINVAL; switch (id) { - case 2: + case LOONGARCH_CPUCFG0: + *v = GENMASK(31, 0); + return 0; + case LOONGARCH_CPUCFG1: + /* CPUCFG1_MSGINT is not supported by KVM */ + *v = GENMASK(25, 0); + return 0; + case LOONGARCH_CPUCFG2: /* CPUCFG2 features unconditionally supported by KVM */ *v = CPUCFG2_FP | CPUCFG2_FPSP | CPUCFG2_FPDP | CPUCFG2_FPVERS | CPUCFG2_LLFTP | CPUCFG2_LLFTPREV | - CPUCFG2_LAM; + CPUCFG2_LSPW | CPUCFG2_LAM; /* * For the ISA extensions listed below, if one is supported * by the host, then it is also supported by KVM. @@ -318,14 +325,26 @@ static int _kvm_get_cpucfg_mask(int id, u64 *v) if (cpu_has_lasx) *v |= CPUCFG2_LASX; + return 0; + case LOONGARCH_CPUCFG3: + *v = GENMASK(16, 0); + return 0; + case LOONGARCH_CPUCFG4: + case LOONGARCH_CPUCFG5: + *v = GENMASK(31, 0); + return 0; + case LOONGARCH_CPUCFG16: + *v = GENMASK(16, 0); + return 0; + case LOONGARCH_CPUCFG17 ... LOONGARCH_CPUCFG20: + *v = GENMASK(30, 0); return 0; default: /* - * No restrictions on other valid CPUCFG IDs' values, but - * CPUCFG data is limited to 32 bits as the LoongArch ISA - * manual says (Volume 1, Section 2.2.10.5 "CPUCFG"). + * CPUCFG bits should be zero if reserved by HW or not + * supported by KVM. */ - *v = U32_MAX; + *v = 0; return 0; } } @@ -344,7 +363,7 @@ static int kvm_check_cpucfg(int id, u64 val) return -EINVAL; switch (id) { - case 2: + case LOONGARCH_CPUCFG2: if (!(val & CPUCFG2_LLFTP)) /* Guests must have a constant timer */ return -EINVAL; From 8bc15d02d5fdff31bfeca02e58e22e26880dde39 Mon Sep 17 00:00:00 2001 From: Bibo Mao Date: Wed, 6 Mar 2024 09:12:13 +0800 Subject: [PATCH 2/4] LoongArch: KVM: Start SW timer only when vcpu is blocking SW timer is enabled when vcpu thread is scheduled out, and it is to wake up vcpu from blocked queue. If vcpu thread is scheduled out but is not blocked, such as it is preempted by other threads, it is not necessary to enable SW timer. Since vcpu thread is still on running queue if it is preempted and SW timer is only to wake up vcpu on blocking queue, so SW timer is not useful in this situation. This patch enables SW timer only when vcpu is scheduled out and is blocking. Signed-off-by: Bibo Mao Signed-off-by: Huacai Chen --- arch/loongarch/kvm/timer.c | 23 +++++++++-------------- 1 file changed, 9 insertions(+), 14 deletions(-) diff --git a/arch/loongarch/kvm/timer.c b/arch/loongarch/kvm/timer.c index 111328f60872..b0dafe0611ab 100644 --- a/arch/loongarch/kvm/timer.c +++ b/arch/loongarch/kvm/timer.c @@ -93,7 +93,8 @@ void kvm_restore_timer(struct kvm_vcpu *vcpu) /* * Freeze the soft-timer and sync the guest stable timer with it. */ - hrtimer_cancel(&vcpu->arch.swtimer); + if (kvm_vcpu_is_blocking(vcpu)) + hrtimer_cancel(&vcpu->arch.swtimer); /* * From LoongArch Reference Manual Volume 1 Chapter 7.6.2 @@ -168,26 +169,20 @@ static void _kvm_save_timer(struct kvm_vcpu *vcpu) * Here judge one-shot timer fired by checking whether TVAL is larger * than TCFG */ - if (ticks < cfg) { + if (ticks < cfg) delta = tick_to_ns(vcpu, ticks); - expire = ktime_add_ns(ktime_get(), delta); - vcpu->arch.expire = expire; + else + delta = 0; + + expire = ktime_add_ns(ktime_get(), delta); + vcpu->arch.expire = expire; + if (kvm_vcpu_is_blocking(vcpu)) { /* * HRTIMER_MODE_PINNED is suggested since vcpu may run in * the same physical cpu in next time */ hrtimer_start(&vcpu->arch.swtimer, expire, HRTIMER_MODE_ABS_PINNED); - } else if (vcpu->stat.generic.blocking) { - /* - * Inject timer interrupt so that halt polling can dectect and exit. - * VCPU is scheduled out already and sleeps in rcuwait queue and - * will not poll pending events again. kvm_queue_irq() is not enough, - * hrtimer swtimer should be used here. - */ - expire = ktime_add_ns(ktime_get(), 10); - vcpu->arch.expire = expire; - hrtimer_start(&vcpu->arch.swtimer, expire, HRTIMER_MODE_ABS_PINNED); } } From f66228053e429bd926505c447d3af2d3d610ed92 Mon Sep 17 00:00:00 2001 From: Bibo Mao Date: Wed, 6 Mar 2024 09:12:13 +0800 Subject: [PATCH 3/4] LoongArch: KVM: Do not restart SW timer when it is expired LoongArch VCPUs have their own separate HW timers. SW timer is to wake up blocked vcpu thread, rather than HW timer emulation. When blocking vcpu scheduled out, SW timer is used to wakeup blocked vcpu thread and injects timer interrupt. It does not care about whether guest timer is in period mode or oneshot mode, and SW timer needs not to be restarted since vcpu has been woken. This patch does not restart SW timer when it is expired. Signed-off-by: Bibo Mao Signed-off-by: Huacai Chen --- arch/loongarch/kvm/timer.c | 20 +------------------- 1 file changed, 1 insertion(+), 19 deletions(-) diff --git a/arch/loongarch/kvm/timer.c b/arch/loongarch/kvm/timer.c index b0dafe0611ab..bcc6b6d063d9 100644 --- a/arch/loongarch/kvm/timer.c +++ b/arch/loongarch/kvm/timer.c @@ -23,24 +23,6 @@ static inline u64 tick_to_ns(struct kvm_vcpu *vcpu, u64 tick) return div_u64(tick * MNSEC_PER_SEC, vcpu->arch.timer_mhz); } -/* - * Push timer forward on timeout. - * Handle an hrtimer event by push the hrtimer forward a period. - */ -static enum hrtimer_restart kvm_count_timeout(struct kvm_vcpu *vcpu) -{ - unsigned long cfg, period; - - /* Add periodic tick to current expire time */ - cfg = kvm_read_sw_gcsr(vcpu->arch.csr, LOONGARCH_CSR_TCFG); - if (cfg & CSR_TCFG_PERIOD) { - period = tick_to_ns(vcpu, cfg & CSR_TCFG_VAL); - hrtimer_add_expires_ns(&vcpu->arch.swtimer, period); - return HRTIMER_RESTART; - } else - return HRTIMER_NORESTART; -} - /* Low level hrtimer wake routine */ enum hrtimer_restart kvm_swtimer_wakeup(struct hrtimer *timer) { @@ -50,7 +32,7 @@ enum hrtimer_restart kvm_swtimer_wakeup(struct hrtimer *timer) kvm_queue_irq(vcpu, INT_TI); rcuwait_wake_up(&vcpu->wait); - return kvm_count_timeout(vcpu); + return HRTIMER_NORESTART; } /* From b99f783106ea5b2f8c9d74f4d3b1e2f77af9ec6e Mon Sep 17 00:00:00 2001 From: Bibo Mao Date: Wed, 6 Mar 2024 09:12:13 +0800 Subject: [PATCH 4/4] LoongArch: KVM: Remove unnecessary CSR register saving during enter guest Some CSR registers like CRMD/PRMD are saved during enter VM mode now. However they are not restored for actual use, so saving for these CSR registers can be removed. Reviewed-by: Tianrui Zhao Signed-off-by: Bibo Mao Signed-off-by: Huacai Chen --- arch/loongarch/kvm/switch.S | 6 ------ 1 file changed, 6 deletions(-) diff --git a/arch/loongarch/kvm/switch.S b/arch/loongarch/kvm/switch.S index ba976509bfe8..3634431db18a 100644 --- a/arch/loongarch/kvm/switch.S +++ b/arch/loongarch/kvm/switch.S @@ -213,12 +213,6 @@ SYM_FUNC_START(kvm_enter_guest) /* Save host GPRs */ kvm_save_host_gpr a2 - /* Save host CRMD, PRMD to stack */ - csrrd a3, LOONGARCH_CSR_CRMD - st.d a3, a2, PT_CRMD - csrrd a3, LOONGARCH_CSR_PRMD - st.d a3, a2, PT_PRMD - addi.d a2, a1, KVM_VCPU_ARCH st.d sp, a2, KVM_ARCH_HSP st.d tp, a2, KVM_ARCH_HTP