From 6231c9e1a9f35b535c66709aa8a6eda40dbc4132 Mon Sep 17 00:00:00 2001 From: Prasad Pandit Date: Wed, 3 Jan 2024 13:23:43 +0530 Subject: KVM: x86: make KVM_REQ_NMI request iff NMI pending for vcpu kvm_vcpu_ioctl_x86_set_vcpu_events() routine makes 'KVM_REQ_NMI' request for a vcpu even when its 'events->nmi.pending' is zero. Ex: qemu_thread_start kvm_vcpu_thread_fn qemu_wait_io_event qemu_wait_io_event_common process_queued_cpu_work do_kvm_cpu_synchronize_post_init/_reset kvm_arch_put_registers kvm_put_vcpu_events (cpu, level=[2|3]) This leads vCPU threads in QEMU to constantly acquire & release the global mutex lock, delaying the guest boot due to lock contention. Add check to make KVM_REQ_NMI request only if vcpu has NMI pending. Fixes: bdedff263132 ("KVM: x86: Route pending NMIs from userspace through process_nmi()") Cc: stable@vger.kernel.org Signed-off-by: Prasad Pandit Link: https://lore.kernel.org/r/20240103075343.549293-1-ppandit@redhat.com Signed-off-by: Sean Christopherson --- arch/x86/kvm/x86.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'arch/x86/kvm/x86.c') diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 363b1c080205..25bc52cdf8f4 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -5454,7 +5454,8 @@ static int kvm_vcpu_ioctl_x86_set_vcpu_events(struct kvm_vcpu *vcpu, if (events->flags & KVM_VCPUEVENT_VALID_NMI_PENDING) { vcpu->arch.nmi_pending = 0; atomic_set(&vcpu->arch.nmi_queued, events->nmi.pending); - kvm_make_request(KVM_REQ_NMI, vcpu); + if (events->nmi.pending) + kvm_make_request(KVM_REQ_NMI, vcpu); } static_call(kvm_x86_set_nmi_mask)(vcpu, events->nmi.masked); -- cgit v1.2.3 From 9e05d9b06757732477cca428e87f3d72163d01cf Mon Sep 17 00:00:00 2001 From: Tengfei Yu Date: Thu, 25 Jan 2024 13:08:23 +0800 Subject: KVM: x86: Check irqchip mode before create PIT As the kvm api(https://docs.kernel.org/virt/kvm/api.html) reads, KVM_CREATE_PIT2 call is only valid after enabling in-kernel irqchip support via KVM_CREATE_IRQCHIP. Without this check, I can create PIT first and enable irqchip-split then, which may cause the PIT invalid because of lacking of in-kernel PIC to inject the interrupt. Signed-off-by: Tengfei Yu Message-Id: <20240125050823.4893-1-moehanabichan@gmail.com> Signed-off-by: Paolo Bonzini --- arch/x86/kvm/x86.c | 3 +++ 1 file changed, 3 insertions(+) (limited to 'arch/x86/kvm/x86.c') diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 363b1c080205..9a89471a613c 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -7016,6 +7016,9 @@ set_identity_unlock: r = -EEXIST; if (kvm->arch.vpit) goto create_pit_unlock; + r = -ENOENT; + if (!pic_in_kernel(kvm)) + goto create_pit_unlock; r = -ENOMEM; kvm->arch.vpit = kvm_create_pit(kvm, u.pit_config.flags); if (kvm->arch.vpit) -- cgit v1.2.3 From d52734d00b8e86604a66b4cdfa9e8bb541daca2d Mon Sep 17 00:00:00 2001 From: "Maciej S. Szmigiero" Date: Wed, 24 Jan 2024 21:18:21 +0100 Subject: KVM: x86: Give a hint when Win2016 might fail to boot due to XSAVES erratum Since commit b0563468eeac ("x86/CPU/AMD: Disable XSAVES on AMD family 0x17") kernel unconditionally clears the XSAVES CPU feature bit on Zen1/2 CPUs. Because KVM CPU caps are initialized from the kernel boot CPU features this makes the XSAVES feature also unavailable for KVM guests in this case. At the same time the XSAVEC feature is left enabled. Unfortunately, having XSAVEC but no XSAVES in CPUID breaks Hyper-V enabled Windows Server 2016 VMs that have more than one vCPU. Let's at least give users hint in the kernel log what could be wrong since these VMs currently simply hang at boot with a black screen - giving no clue what suddenly broke them and how to make them work again. Trigger the kernel message hint based on the particular guest ID written to the Guest OS Identity Hyper-V MSR implemented by KVM. Defer this check to when the L1 Hyper-V hypervisor enables SVM in EFER since we want to limit this message to Hyper-V enabled Windows guests only (Windows session running nested as L2) but the actual Guest OS Identity MSR write is done by L1 and happens before it enables SVM. Fixes: b0563468eeac ("x86/CPU/AMD: Disable XSAVES on AMD family 0x17") Signed-off-by: Maciej S. Szmigiero Message-Id: [Move some checks before mutex_lock(), rename function. - Paolo] Signed-off-by: Paolo Bonzini --- arch/x86/include/asm/kvm_host.h | 2 ++ arch/x86/kvm/hyperv.c | 50 +++++++++++++++++++++++++++++++++++++++++ arch/x86/kvm/hyperv.h | 3 +++ arch/x86/kvm/x86.c | 4 ++++ 4 files changed, 59 insertions(+) (limited to 'arch/x86/kvm/x86.c') diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index b5b2d0fde579..d271ba20a0b2 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -1145,6 +1145,8 @@ struct kvm_hv { unsigned int synic_auto_eoi_used; struct kvm_hv_syndbg hv_syndbg; + + bool xsaves_xsavec_checked; }; #endif diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c index 4943f6b2bbee..8a47f8541eab 100644 --- a/arch/x86/kvm/hyperv.c +++ b/arch/x86/kvm/hyperv.c @@ -1322,6 +1322,56 @@ static bool hv_check_msr_access(struct kvm_vcpu_hv *hv_vcpu, u32 msr) return false; } +#define KVM_HV_WIN2016_GUEST_ID 0x1040a00003839 +#define KVM_HV_WIN2016_GUEST_ID_MASK (~GENMASK_ULL(23, 16)) /* mask out the service version */ + +/* + * Hyper-V enabled Windows Server 2016 SMP VMs fail to boot in !XSAVES && XSAVEC + * configuration. + * Such configuration can result from, for example, AMD Erratum 1386 workaround. + * + * Print a notice so users aren't left wondering what's suddenly gone wrong. + */ +static void __kvm_hv_xsaves_xsavec_maybe_warn(struct kvm_vcpu *vcpu) +{ + struct kvm *kvm = vcpu->kvm; + struct kvm_hv *hv = to_kvm_hv(kvm); + + /* Check again under the hv_lock. */ + if (hv->xsaves_xsavec_checked) + return; + + if ((hv->hv_guest_os_id & KVM_HV_WIN2016_GUEST_ID_MASK) != + KVM_HV_WIN2016_GUEST_ID) + return; + + hv->xsaves_xsavec_checked = true; + + /* UP configurations aren't affected */ + if (atomic_read(&kvm->online_vcpus) < 2) + return; + + if (guest_cpuid_has(vcpu, X86_FEATURE_XSAVES) || + !guest_cpuid_has(vcpu, X86_FEATURE_XSAVEC)) + return; + + pr_notice_ratelimited("Booting SMP Windows KVM VM with !XSAVES && XSAVEC. " + "If it fails to boot try disabling XSAVEC in the VM config.\n"); +} + +void kvm_hv_xsaves_xsavec_maybe_warn(struct kvm_vcpu *vcpu) +{ + struct kvm_hv *hv = to_kvm_hv(vcpu->kvm); + + if (!vcpu->arch.hyperv_enabled || + hv->xsaves_xsavec_checked) + return; + + mutex_lock(&hv->hv_lock); + __kvm_hv_xsaves_xsavec_maybe_warn(vcpu); + mutex_unlock(&hv->hv_lock); +} + static int kvm_hv_set_msr_pw(struct kvm_vcpu *vcpu, u32 msr, u64 data, bool host) { diff --git a/arch/x86/kvm/hyperv.h b/arch/x86/kvm/hyperv.h index 1dc0b6604526..923e64903da9 100644 --- a/arch/x86/kvm/hyperv.h +++ b/arch/x86/kvm/hyperv.h @@ -182,6 +182,8 @@ void kvm_hv_setup_tsc_page(struct kvm *kvm, struct pvclock_vcpu_time_info *hv_clock); void kvm_hv_request_tsc_page_update(struct kvm *kvm); +void kvm_hv_xsaves_xsavec_maybe_warn(struct kvm_vcpu *vcpu); + void kvm_hv_init_vm(struct kvm *kvm); void kvm_hv_destroy_vm(struct kvm *kvm); int kvm_hv_vcpu_init(struct kvm_vcpu *vcpu); @@ -267,6 +269,7 @@ int kvm_hv_vcpu_flush_tlb(struct kvm_vcpu *vcpu); static inline void kvm_hv_setup_tsc_page(struct kvm *kvm, struct pvclock_vcpu_time_info *hv_clock) {} static inline void kvm_hv_request_tsc_page_update(struct kvm *kvm) {} +static inline void kvm_hv_xsaves_xsavec_maybe_warn(struct kvm_vcpu *vcpu) {} static inline void kvm_hv_init_vm(struct kvm *kvm) {} static inline void kvm_hv_destroy_vm(struct kvm *kvm) {} static inline int kvm_hv_vcpu_init(struct kvm_vcpu *vcpu) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 9a89471a613c..bf10a9073a09 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -1782,6 +1782,10 @@ static int set_efer(struct kvm_vcpu *vcpu, struct msr_data *msr_info) if ((efer ^ old_efer) & KVM_MMU_EFER_ROLE_BITS) kvm_mmu_reset_context(vcpu); + if (!static_cpu_has(X86_FEATURE_XSAVES) && + (efer & EFER_SVME)) + kvm_hv_xsaves_xsavec_maybe_warn(vcpu); + return 0; } -- cgit v1.2.3 From 9e62797fd7e8eef9c8a3f7b54b57fbc9caf6a20a Mon Sep 17 00:00:00 2001 From: Vitaly Kuznetsov Date: Tue, 9 Jan 2024 15:11:21 +0100 Subject: KVM: x86: Make gtod_is_based_on_tsc() return 'bool' gtod_is_based_on_tsc() is boolean in nature, i.e. it returns '1' for good clocksources and '0' otherwise. Moreover, its result is used raw by kvm_get_time_and_clockread()/kvm_get_walltime_and_clockread() which are 'bool'. No functional change intended. Signed-off-by: Vitaly Kuznetsov Link: https://lore.kernel.org/r/20240109141121.1619463-6-vkuznets@redhat.com Signed-off-by: Sean Christopherson --- arch/x86/kvm/x86.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'arch/x86/kvm/x86.c') diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 363b1c080205..aa27aec10860 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -2507,7 +2507,7 @@ static u64 compute_guest_tsc(struct kvm_vcpu *vcpu, s64 kernel_ns) } #ifdef CONFIG_X86_64 -static inline int gtod_is_based_on_tsc(int mode) +static inline bool gtod_is_based_on_tsc(int mode) { return mode == VDSO_CLOCKMODE_TSC || mode == VDSO_CLOCKMODE_HVCLOCK; } -- cgit v1.2.3 From 3376ca3f1a2075eaa23c5576c47d04d7e8a4adda Mon Sep 17 00:00:00 2001 From: Mathias Krause Date: Sat, 3 Feb 2024 13:45:20 +0100 Subject: KVM: x86: Fix KVM_GET_MSRS stack info leak Commit 6abe9c1386e5 ("KVM: X86: Move ignore_msrs handling upper the stack") changed the 'ignore_msrs' handling, including sanitizing return values to the caller. This was fine until commit 12bc2132b15e ("KVM: X86: Do the same ignore_msrs check for feature msrs") which allowed non-existing feature MSRs to be ignored, i.e. to not generate an error on the ioctl() level. It even tried to preserve the sanitization of the return value. However, the logic is flawed, as '*data' will be overwritten again with the uninitialized stack value of msr.data. Fix this by simplifying the logic and always initializing msr.data, vanishing the need for an additional error exit path. Fixes: 12bc2132b15e ("KVM: X86: Do the same ignore_msrs check for feature msrs") Signed-off-by: Mathias Krause Reviewed-by: Xiaoyao Li Link: https://lore.kernel.org/r/20240203124522.592778-2-minipli@grsecurity.net Signed-off-by: Sean Christopherson --- arch/x86/kvm/x86.c | 15 +++++---------- 1 file changed, 5 insertions(+), 10 deletions(-) (limited to 'arch/x86/kvm/x86.c') diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 25bc52cdf8f4..3f6e82fd37f3 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -1704,22 +1704,17 @@ static int do_get_msr_feature(struct kvm_vcpu *vcpu, unsigned index, u64 *data) struct kvm_msr_entry msr; int r; + /* Unconditionally clear the output for simplicity */ + msr.data = 0; msr.index = index; r = kvm_get_msr_feature(&msr); - if (r == KVM_MSR_RET_INVALID) { - /* Unconditionally clear the output for simplicity */ - *data = 0; - if (kvm_msr_ignored_check(index, 0, false)) - r = 0; - } - - if (r) - return r; + if (r == KVM_MSR_RET_INVALID && kvm_msr_ignored_check(index, 0, false)) + r = 0; *data = msr.data; - return 0; + return r; } static bool __kvm_valid_efer(struct kvm_vcpu *vcpu, u64 efer) -- cgit v1.2.3