From 7e34fbd05c6350b30161be84d4f8954c9d321292 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Wed, 23 Sep 2020 11:03:55 -0700 Subject: [PATCH] KVM: x86: Rename "shared_msrs" to "user_return_msrs" Rename the "shared_msrs" mechanism, which is used to defer restoring MSRs that are only consumed when running in userspace, to a more banal but less likely to be confusing "user_return_msrs". The "shared" nomenclature is confusing as it's not obvious who is sharing what, e.g. reasonable interpretations are that the guest value is shared by vCPUs in a VM, or that the MSR value is shared/common to guest and host, both of which are wrong. "shared" is also misleading as the MSR value (in hardware) is not guaranteed to be shared/reused between VMs (if that's indeed the correct interpretation of the name), as the ability to share values between VMs is simply a side effect (albiet a very nice side effect) of deferring restoration of the host value until returning from userspace. "user_return" avoids the above confusion by describing the mechanism itself instead of its effects. Signed-off-by: Sean Christopherson Message-Id: <20200923180409.32255-2-sean.j.christopherson@intel.com> Signed-off-by: Paolo Bonzini --- arch/x86/include/asm/kvm_host.h | 4 +- arch/x86/kvm/vmx/vmx.c | 11 ++--- arch/x86/kvm/x86.c | 101 +++++++++++++++++++++------------------- 3 files changed, 60 insertions(+), 56 deletions(-) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 3f0ccb6..5d4c39c3 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -1617,8 +1617,8 @@ int kvm_pv_send_ipi(struct kvm *kvm, unsigned long ipi_bitmap_low, unsigned long ipi_bitmap_high, u32 min, unsigned long icr, int op_64_bit); -void kvm_define_shared_msr(unsigned index, u32 msr); -int kvm_set_shared_msr(unsigned index, u64 val, u64 mask); +void kvm_define_user_return_msr(unsigned index, u32 msr); +int kvm_set_user_return_msr(unsigned index, u64 val, u64 mask); u64 kvm_scale_tsc(struct kvm_vcpu *vcpu, u64 tsc); u64 kvm_read_l1_tsc(struct kvm_vcpu *vcpu, u64 host_tsc); diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index bac423a..b41649e 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -639,8 +639,7 @@ static int vmx_set_guest_msr(struct vcpu_vmx *vmx, struct shared_msr_entry *msr, msr->data = data; if (msr - vmx->guest_msrs < vmx->save_nmsrs) { preempt_disable(); - ret = kvm_set_shared_msr(msr->index, msr->data, - msr->mask); + ret = kvm_set_user_return_msr(msr->index, msr->data, msr->mask); preempt_enable(); if (ret) msr->data = old_msr_data; @@ -1138,9 +1137,9 @@ void vmx_prepare_switch_to_guest(struct kvm_vcpu *vcpu) if (!vmx->guest_msrs_ready) { vmx->guest_msrs_ready = true; for (i = 0; i < vmx->save_nmsrs; ++i) - kvm_set_shared_msr(vmx->guest_msrs[i].index, - vmx->guest_msrs[i].data, - vmx->guest_msrs[i].mask); + kvm_set_user_return_msr(vmx->guest_msrs[i].index, + vmx->guest_msrs[i].data, + vmx->guest_msrs[i].mask); } @@ -7582,7 +7581,7 @@ static __init int hardware_setup(void) host_idt_base = dt.address; for (i = 0; i < ARRAY_SIZE(vmx_msr_index); ++i) - kvm_define_shared_msr(i, vmx_msr_index[i]); + kvm_define_user_return_msr(i, vmx_msr_index[i]); if (setup_vmcs_config(&vmcs_config, &vmx_capability) < 0) return -EIO; diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index b4c581c..a547b00 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -162,24 +162,29 @@ module_param(force_emulation_prefix, bool, S_IRUGO); int __read_mostly pi_inject_timer = -1; module_param(pi_inject_timer, bint, S_IRUGO | S_IWUSR); -#define KVM_NR_SHARED_MSRS 16 +/* + * Restoring the host value for MSRs that are only consumed when running in + * usermode, e.g. SYSCALL MSRs and TSC_AUX, can be deferred until the CPU + * returns to userspace, i.e. the kernel can run with the guest's value. + */ +#define KVM_MAX_NR_USER_RETURN_MSRS 16 -struct kvm_shared_msrs_global { +struct kvm_user_return_msrs_global { int nr; - u32 msrs[KVM_NR_SHARED_MSRS]; + u32 msrs[KVM_MAX_NR_USER_RETURN_MSRS]; }; -struct kvm_shared_msrs { +struct kvm_user_return_msrs { struct user_return_notifier urn; bool registered; - struct kvm_shared_msr_values { + struct kvm_user_return_msr_values { u64 host; u64 curr; - } values[KVM_NR_SHARED_MSRS]; + } values[KVM_MAX_NR_USER_RETURN_MSRS]; }; -static struct kvm_shared_msrs_global __read_mostly shared_msrs_global; -static struct kvm_shared_msrs __percpu *shared_msrs; +static struct kvm_user_return_msrs_global __read_mostly user_return_msrs_global; +static struct kvm_user_return_msrs __percpu *user_return_msrs; #define KVM_SUPPORTED_XCR0 (XFEATURE_MASK_FP | XFEATURE_MASK_SSE \ | XFEATURE_MASK_YMM | XFEATURE_MASK_BNDREGS \ @@ -294,9 +299,9 @@ static inline void kvm_async_pf_hash_reset(struct kvm_vcpu *vcpu) static void kvm_on_user_return(struct user_return_notifier *urn) { unsigned slot; - struct kvm_shared_msrs *locals - = container_of(urn, struct kvm_shared_msrs, urn); - struct kvm_shared_msr_values *values; + struct kvm_user_return_msrs *msrs + = container_of(urn, struct kvm_user_return_msrs, urn); + struct kvm_user_return_msr_values *values; unsigned long flags; /* @@ -304,73 +309,73 @@ static void kvm_on_user_return(struct user_return_notifier *urn) * interrupted and executed through kvm_arch_hardware_disable() */ local_irq_save(flags); - if (locals->registered) { - locals->registered = false; + if (msrs->registered) { + msrs->registered = false; user_return_notifier_unregister(urn); } local_irq_restore(flags); - for (slot = 0; slot < shared_msrs_global.nr; ++slot) { - values = &locals->values[slot]; + for (slot = 0; slot < user_return_msrs_global.nr; ++slot) { + values = &msrs->values[slot]; if (values->host != values->curr) { - wrmsrl(shared_msrs_global.msrs[slot], values->host); + wrmsrl(user_return_msrs_global.msrs[slot], values->host); values->curr = values->host; } } } -void kvm_define_shared_msr(unsigned slot, u32 msr) +void kvm_define_user_return_msr(unsigned slot, u32 msr) { - BUG_ON(slot >= KVM_NR_SHARED_MSRS); - shared_msrs_global.msrs[slot] = msr; - if (slot >= shared_msrs_global.nr) - shared_msrs_global.nr = slot + 1; + BUG_ON(slot >= KVM_MAX_NR_USER_RETURN_MSRS); + user_return_msrs_global.msrs[slot] = msr; + if (slot >= user_return_msrs_global.nr) + user_return_msrs_global.nr = slot + 1; } -EXPORT_SYMBOL_GPL(kvm_define_shared_msr); +EXPORT_SYMBOL_GPL(kvm_define_user_return_msr); -static void kvm_shared_msr_cpu_online(void) +static void kvm_user_return_msr_cpu_online(void) { unsigned int cpu = smp_processor_id(); - struct kvm_shared_msrs *smsr = per_cpu_ptr(shared_msrs, cpu); + struct kvm_user_return_msrs *msrs = per_cpu_ptr(user_return_msrs, cpu); u64 value; int i; - for (i = 0; i < shared_msrs_global.nr; ++i) { - rdmsrl_safe(shared_msrs_global.msrs[i], &value); - smsr->values[i].host = value; - smsr->values[i].curr = value; + for (i = 0; i < user_return_msrs_global.nr; ++i) { + rdmsrl_safe(user_return_msrs_global.msrs[i], &value); + msrs->values[i].host = value; + msrs->values[i].curr = value; } } -int kvm_set_shared_msr(unsigned slot, u64 value, u64 mask) +int kvm_set_user_return_msr(unsigned slot, u64 value, u64 mask) { unsigned int cpu = smp_processor_id(); - struct kvm_shared_msrs *smsr = per_cpu_ptr(shared_msrs, cpu); + struct kvm_user_return_msrs *msrs = per_cpu_ptr(user_return_msrs, cpu); int err; - value = (value & mask) | (smsr->values[slot].host & ~mask); - if (value == smsr->values[slot].curr) + value = (value & mask) | (msrs->values[slot].host & ~mask); + if (value == msrs->values[slot].curr) return 0; - err = wrmsrl_safe(shared_msrs_global.msrs[slot], value); + err = wrmsrl_safe(user_return_msrs_global.msrs[slot], value); if (err) return 1; - smsr->values[slot].curr = value; - if (!smsr->registered) { - smsr->urn.on_user_return = kvm_on_user_return; - user_return_notifier_register(&smsr->urn); - smsr->registered = true; + msrs->values[slot].curr = value; + if (!msrs->registered) { + msrs->urn.on_user_return = kvm_on_user_return; + user_return_notifier_register(&msrs->urn); + msrs->registered = true; } return 0; } -EXPORT_SYMBOL_GPL(kvm_set_shared_msr); +EXPORT_SYMBOL_GPL(kvm_set_user_return_msr); static void drop_user_return_notifiers(void) { unsigned int cpu = smp_processor_id(); - struct kvm_shared_msrs *smsr = per_cpu_ptr(shared_msrs, cpu); + struct kvm_user_return_msrs *msrs = per_cpu_ptr(user_return_msrs, cpu); - if (smsr->registered) - kvm_on_user_return(&smsr->urn); + if (msrs->registered) + kvm_on_user_return(&msrs->urn); } u64 kvm_get_apic_base(struct kvm_vcpu *vcpu) @@ -7529,9 +7534,9 @@ int kvm_arch_init(void *opaque) goto out_free_x86_fpu_cache; } - shared_msrs = alloc_percpu(struct kvm_shared_msrs); - if (!shared_msrs) { - printk(KERN_ERR "kvm: failed to allocate percpu kvm_shared_msrs\n"); + user_return_msrs = alloc_percpu(struct kvm_user_return_msrs); + if (!user_return_msrs) { + printk(KERN_ERR "kvm: failed to allocate percpu kvm_user_return_msrs\n"); goto out_free_x86_emulator_cache; } @@ -7564,7 +7569,7 @@ int kvm_arch_init(void *opaque) return 0; out_free_percpu: - free_percpu(shared_msrs); + free_percpu(user_return_msrs); out_free_x86_emulator_cache: kmem_cache_destroy(x86_emulator_cache); out_free_x86_fpu_cache: @@ -7591,7 +7596,7 @@ void kvm_arch_exit(void) #endif kvm_x86_ops.hardware_enable = NULL; kvm_mmu_module_exit(); - free_percpu(shared_msrs); + free_percpu(user_return_msrs); kmem_cache_destroy(x86_fpu_cache); } @@ -9722,7 +9727,7 @@ int kvm_arch_hardware_enable(void) u64 max_tsc = 0; bool stable, backwards_tsc = false; - kvm_shared_msr_cpu_online(); + kvm_user_return_msr_cpu_online(); ret = kvm_x86_ops.hardware_enable(); if (ret != 0) return ret; -- 2.7.4