lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Wed, 2 Nov 2022 23:19:05 +0000 From: Sean Christopherson <seanjc@...gle.com> To: Paolo Bonzini <pbonzini@...hat.com>, Marc Zyngier <maz@...nel.org>, Huacai Chen <chenhuacai@...nel.org>, Aleksandar Markovic <aleksandar.qemu.devel@...il.com>, Anup Patel <anup@...infault.org>, Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>, Christian Borntraeger <borntraeger@...ux.ibm.com>, Janosch Frank <frankja@...ux.ibm.com>, Claudio Imbrenda <imbrenda@...ux.ibm.com>, Matthew Rosato <mjrosato@...ux.ibm.com>, Eric Farman <farman@...ux.ibm.com>, Sean Christopherson <seanjc@...gle.com>, Vitaly Kuznetsov <vkuznets@...hat.com> Cc: James Morse <james.morse@....com>, Alexandru Elisei <alexandru.elisei@....com>, Suzuki K Poulose <suzuki.poulose@....com>, Oliver Upton <oliver.upton@...ux.dev>, Atish Patra <atishp@...shpatra.org>, David Hildenbrand <david@...hat.com>, kvm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev, kvmarm@...ts.cs.columbia.edu, linux-mips@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org, kvm-riscv@...ts.infradead.org, linux-riscv@...ts.infradead.org, linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org, Isaku Yamahata <isaku.yamahata@...el.com>, Fabiano Rosas <farosas@...ux.ibm.com>, Michael Ellerman <mpe@...erman.id.au>, Chao Gao <chao.gao@...el.com>, Thomas Gleixner <tglx@...utronix.de>, Yuan Yao <yuan.yao@...el.com> Subject: [PATCH 38/44] KVM: Disable CPU hotplug during hardware enabling From: Chao Gao <chao.gao@...el.com> Disable CPU hotplug during hardware_enable_all() to prevent the corner case where if the following sequence occurs: 1. A hotplugged CPU marks itself online in cpu_online_mask 2. The hotplugged CPU enables interrupt before invoking KVM's ONLINE callback 3 hardware_enable_all() is invoked on another CPU right the hotplugged CPU will be included in on_each_cpu() and thus get sent through hardware_enable_nolock() before kvm_online_cpu() is called. start_secondary { ... set_cpu_online(smp_processor_id(), true); <- 1 ... local_irq_enable(); <- 2 ... cpu_startup_entry(CPUHP_AP_ONLINE_IDLE); <- 3 } KVM currently fudges around this race by keeping track of which CPUs have done hardware enabling (see commit 1b6c016818a5 "KVM: Keep track of which cpus have virtualization enabled"), but that's an inefficient, convoluted, and hacky solution. Signed-off-by: Chao Gao <chao.gao@...el.com> [sean: split to separate patch, write changelog] Signed-off-by: Sean Christopherson <seanjc@...gle.com> --- arch/x86/kvm/x86.c | 8 +++++++- virt/kvm/kvm_main.c | 10 ++++++++++ 2 files changed, 17 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index a7b1d916ecb2..a15e54ba0471 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -9283,7 +9283,13 @@ static int kvm_x86_check_processor_compatibility(struct kvm_x86_init_ops *ops) int cpu = smp_processor_id(); struct cpuinfo_x86 *c = &cpu_data(cpu); - WARN_ON(!irqs_disabled()); + /* + * Compatibility checks are done when loading KVM and when enabling + * hardware, e.g. during CPU hotplug, to ensure all online CPUs are + * compatible, i.e. KVM should never perform a compatibility check on + * an offline CPU. + */ + WARN_ON(!irqs_disabled() && cpu_active(cpu)); if (__cr4_reserved_bits(cpu_has, c) != __cr4_reserved_bits(cpu_has, &boot_cpu_data)) diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index fd9e39c85549..4e765ef9f4bd 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -5088,6 +5088,15 @@ static int hardware_enable_all(void) { int r = 0; + /* + * When onlining a CPU, cpu_online_mask is set before kvm_online_cpu() + * is called, and so on_each_cpu() between them includes the CPU that + * is being onlined. As a result, hardware_enable_nolock() may get + * invoked before kvm_online_cpu(). + * + * Disable CPU hotplug to prevent scenarios where KVM sees + */ + cpus_read_lock(); raw_spin_lock(&kvm_count_lock); kvm_usage_count++; @@ -5102,6 +5111,7 @@ static int hardware_enable_all(void) } raw_spin_unlock(&kvm_count_lock); + cpus_read_unlock(); return r; } -- 2.38.1.431.g37b22c650d-goog
Powered by blists - more mailing lists