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[73.143.21.186]) by smtp.gmail.com with ESMTPSA id fh3-20020a05622a588300b00425b356b919sm4240208qtb.55.2023.12.13.18.47.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 13 Dec 2023 18:47:33 -0800 (PST) From: "Vineeth Pillai (Google)" To: Ben Segall , Borislav Petkov , Daniel Bristot de Oliveira , Dave Hansen , Dietmar Eggemann , "H . Peter Anvin" , Ingo Molnar , Juri Lelli , Mel Gorman , Paolo Bonzini , Andy Lutomirski , Peter Zijlstra , Sean Christopherson , Steven Rostedt , Thomas Gleixner , Valentin Schneider , Vincent Guittot , Vitaly Kuznetsov , Wanpeng Li Cc: "Vineeth Pillai (Google)" , Suleiman Souhlal , Masami Hiramatsu , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, x86@kernel.org, Joel Fernandes Subject: [RFC PATCH 1/8] kvm: x86: MSR for setting up scheduler info shared memory Date: Wed, 13 Dec 2023 21:47:18 -0500 Message-ID: <20231214024727.3503870-2-vineeth@bitbyteword.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20231214024727.3503870-1-vineeth@bitbyteword.org> References: <20231214024727.3503870-1-vineeth@bitbyteword.org> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Implement a kvm MSR that guest uses to provide the GPA of shared memory for communicating the scheduling information between host and guest. wrmsr(0) disables the feature. wrmsr(valid_gpa) enables the feature and uses the gpa for further communication. Also add a new cpuid feature flag for the host to advertise the feature to the guest. Co-developed-by: Joel Fernandes (Google) Signed-off-by: Joel Fernandes (Google) Signed-off-by: Vineeth Pillai (Google) --- arch/x86/include/asm/kvm_host.h | 25 ++++++++++++ arch/x86/include/uapi/asm/kvm_para.h | 24 +++++++++++ arch/x86/kvm/Kconfig | 12 ++++++ arch/x86/kvm/cpuid.c | 2 + arch/x86/kvm/x86.c | 61 ++++++++++++++++++++++++++++ include/linux/kvm_host.h | 5 +++ 6 files changed, 129 insertions(+) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index f72b30d2238a..f89ba1f07d88 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -987,6 +987,18 @@ struct kvm_vcpu_arch { /* Protected Guests */ bool guest_state_protected; +#ifdef CONFIG_PARAVIRT_SCHED_KVM + /* + * MSR to setup a shared memory for scheduling + * information sharing between host and guest. + */ + struct { + enum kvm_vcpu_boost_state boost_status; + u64 msr_val; + struct gfn_to_hva_cache data; + } pv_sched; +#endif + /* * Set when PDPTS were loaded directly by the userspace without * reading the guest memory @@ -2217,4 +2229,17 @@ int memslot_rmap_alloc(struct kvm_memory_slot *slot, unsigned long npages); */ #define KVM_EXIT_HYPERCALL_MBZ GENMASK_ULL(31, 1) +#ifdef CONFIG_PARAVIRT_SCHED_KVM +static inline bool kvm_arch_vcpu_pv_sched_enabled(struct kvm_vcpu_arch *arch) +{ + return arch->pv_sched.msr_val; +} + +static inline void kvm_arch_vcpu_set_boost_status(struct kvm_vcpu_arch *arch, + enum kvm_vcpu_boost_state boost_status) +{ + arch->pv_sched.boost_status = boost_status; +} +#endif + #endif /* _ASM_X86_KVM_HOST_H */ diff --git a/arch/x86/include/uapi/asm/kvm_para.h b/arch/x86/include/uapi/asm/kvm_para.h index 6e64b27b2c1e..6b1dea07a563 100644 --- a/arch/x86/include/uapi/asm/kvm_para.h +++ b/arch/x86/include/uapi/asm/kvm_para.h @@ -36,6 +36,7 @@ #define KVM_FEATURE_MSI_EXT_DEST_ID 15 #define KVM_FEATURE_HC_MAP_GPA_RANGE 16 #define KVM_FEATURE_MIGRATION_CONTROL 17 +#define KVM_FEATURE_PV_SCHED 18 #define KVM_HINTS_REALTIME 0 @@ -58,6 +59,7 @@ #define MSR_KVM_ASYNC_PF_INT 0x4b564d06 #define MSR_KVM_ASYNC_PF_ACK 0x4b564d07 #define MSR_KVM_MIGRATION_CONTROL 0x4b564d08 +#define MSR_KVM_PV_SCHED 0x4b564da0 struct kvm_steal_time { __u64 steal; @@ -150,4 +152,26 @@ struct kvm_vcpu_pv_apf_data { #define KVM_PV_EOI_ENABLED KVM_PV_EOI_MASK #define KVM_PV_EOI_DISABLED 0x0 +/* + * VCPU boost state shared between the host and guest. + */ +enum kvm_vcpu_boost_state { + /* Priority boosting feature disabled in host */ + VCPU_BOOST_DISABLED = 0, + /* + * vcpu is not explicitly boosted by the host. + * (Default priority when the guest started) + */ + VCPU_BOOST_NORMAL, + /* vcpu is boosted by the host */ + VCPU_BOOST_BOOSTED +}; + +/* + * Structure passed in via MSR_KVM_PV_SCHED + */ +struct pv_sched_data { + __u64 boost_status; +}; + #endif /* _UAPI_ASM_X86_KVM_PARA_H */ diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig index 89ca7f4c1464..dbcba73fb508 100644 --- a/arch/x86/kvm/Kconfig +++ b/arch/x86/kvm/Kconfig @@ -141,4 +141,16 @@ config KVM_XEN config KVM_EXTERNAL_WRITE_TRACKING bool +config PARAVIRT_SCHED_KVM + bool "Enable paravirt scheduling capability for kvm" + depends on KVM + help + Paravirtualized scheduling facilitates the exchange of scheduling + related information between the host and guest through shared memory, + enhancing the efficiency of vCPU thread scheduling by the hypervisor. + An illustrative use case involves dynamically boosting the priority of + a vCPU thread when the guest is executing a latency-sensitive workload + on that specific vCPU. + This config enables paravirt scheduling in the kvm hypervisor. + endif # VIRTUALIZATION diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index 7bdc66abfc92..960ef6e869f2 100644 --- a/arch/x86/kvm/cpuid.c +++ b/arch/x86/kvm/cpuid.c @@ -1113,6 +1113,8 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function) (1 << KVM_FEATURE_POLL_CONTROL) | (1 << KVM_FEATURE_PV_SCHED_YIELD) | (1 << KVM_FEATURE_ASYNC_PF_INT); + if (IS_ENABLED(CONFIG_PARAVIRT_SCHED_KVM)) + entry->eax |= (1 << KVM_FEATURE_PV_SCHED); if (sched_info_on()) entry->eax |= (1 << KVM_FEATURE_STEAL_TIME); diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 7bcf1a76a6ab..0f475b50ac83 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -3879,6 +3879,33 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info) return 1; break; +#ifdef CONFIG_PARAVIRT_SCHED_KVM + case MSR_KVM_PV_SCHED: + if (!guest_pv_has(vcpu, KVM_FEATURE_PV_SCHED)) + return 1; + + if (!(data & KVM_MSR_ENABLED)) + break; + + if (!(data & ~KVM_MSR_ENABLED)) { + /* + * Disable the feature + */ + vcpu->arch.pv_sched.msr_val = 0; + kvm_set_vcpu_boosted(vcpu, false); + } if (!kvm_gfn_to_hva_cache_init(vcpu->kvm, + &vcpu->arch.pv_sched.data, data & ~KVM_MSR_ENABLED, + sizeof(struct pv_sched_data))) { + vcpu->arch.pv_sched.msr_val = data; + kvm_set_vcpu_boosted(vcpu, false); + } else { + pr_warn("MSR_KVM_PV_SCHED: kvm:%p, vcpu:%p, " + "msr value: %llx, kvm_gfn_to_hva_cache_init failed!\n", + vcpu->kvm, vcpu, data & ~KVM_MSR_ENABLED); + } + break; +#endif + case MSR_KVM_POLL_CONTROL: if (!guest_pv_has(vcpu, KVM_FEATURE_POLL_CONTROL)) return 1; @@ -4239,6 +4266,11 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info) msr_info->data = vcpu->arch.pv_eoi.msr_val; break; +#ifdef CONFIG_PARAVIRT_SCHED_KVM + case MSR_KVM_PV_SCHED: + msr_info->data = vcpu->arch.pv_sched.msr_val; + break; +#endif case MSR_KVM_POLL_CONTROL: if (!guest_pv_has(vcpu, KVM_FEATURE_POLL_CONTROL)) return 1; @@ -9820,6 +9852,29 @@ static int complete_hypercall_exit(struct kvm_vcpu *vcpu) return kvm_skip_emulated_instruction(vcpu); } +#ifdef CONFIG_PARAVIRT_SCHED_KVM +static void record_vcpu_boost_status(struct kvm_vcpu *vcpu) +{ + u64 val = vcpu->arch.pv_sched.boost_status; + + if (!kvm_arch_vcpu_pv_sched_enabled(&vcpu->arch)) + return; + + pagefault_disable(); + kvm_write_guest_offset_cached(vcpu->kvm, &vcpu->arch.pv_sched.data, + &val, offsetof(struct pv_sched_data, boost_status), sizeof(u64)); + pagefault_enable(); +} + +void kvm_set_vcpu_boosted(struct kvm_vcpu *vcpu, bool boosted) +{ + kvm_arch_vcpu_set_boost_status(&vcpu->arch, + boosted ? VCPU_BOOST_BOOSTED : VCPU_BOOST_NORMAL); + + kvm_make_request(KVM_REQ_VCPU_BOOST_UPDATE, vcpu); +} +#endif + int kvm_emulate_hypercall(struct kvm_vcpu *vcpu) { unsigned long nr, a0, a1, a2, a3, ret; @@ -10593,6 +10648,12 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu) } if (kvm_check_request(KVM_REQ_STEAL_UPDATE, vcpu)) record_steal_time(vcpu); + +#ifdef CONFIG_PARAVIRT_SCHED_KVM + if (kvm_check_request(KVM_REQ_VCPU_BOOST_UPDATE, vcpu)) + record_vcpu_boost_status(vcpu); +#endif + #ifdef CONFIG_KVM_SMM if (kvm_check_request(KVM_REQ_SMI, vcpu)) process_smi(vcpu); diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index 9d3ac7720da9..a74aeea55347 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -167,6 +167,7 @@ static inline bool is_error_page(struct page *page) #define KVM_REQ_VM_DEAD (1 | KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP) #define KVM_REQ_UNBLOCK 2 #define KVM_REQ_DIRTY_RING_SOFT_FULL 3 +#define KVM_REQ_VCPU_BOOST_UPDATE 6 #define KVM_REQUEST_ARCH_BASE 8 /* @@ -2287,4 +2288,8 @@ static inline void kvm_account_pgtable_pages(void *virt, int nr) /* Max number of entries allowed for each kvm dirty ring */ #define KVM_DIRTY_RING_MAX_ENTRIES 65536 +#ifdef CONFIG_PARAVIRT_SCHED_KVM +void kvm_set_vcpu_boosted(struct kvm_vcpu *vcpu, bool boosted); +#endif + #endif