From 36c9eea0fc0c2f028b924564f9675a424fab83e6 Mon Sep 17 00:00:00 2001 From: Zeng Guang Date: Tue, 19 Apr 2022 23:44:09 +0800 Subject: [PATCH] KVM: Move kvm_arch_vcpu_precreate() under kvm->lock mainline inclusion from mainline-v6.0-rc1 commit 1d5e740d518e02cea46325b3d37135bf9c08982a category: feature feature: IPI Virtualization bugzilla: https://gitee.com/openeuler/intel-kernel/issues/I5ODSC CVE: N/A Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=1d5e740d518e02cea46325b3d37135bf9c08982a Intel-SIG: commit 1d5e740d518e ("KVM: Move kvm_arch_vcpu_precreate() under kvm->lock") ------------------------------------- KVM: Move kvm_arch_vcpu_precreate() under kvm->lock kvm_arch_vcpu_precreate() targets to handle arch specific VM resource to be prepared prior to the actual creation of vCPU. For example, x86 platform may need do per-VM allocation based on max_vcpu_ids at the first vCPU creation. It probably leads to concurrency control on this allocation as multiple vCPU creation could happen simultaneously. From the architectual point of view, it's necessary to execute kvm_arch_vcpu_precreate() under protect of kvm->lock. Currently only arm64, x86 and s390 have non-nop implementations at the stage of vCPU pre-creation. Remove the lock acquiring in s390's design and make sure all architecture can run kvm_arch_vcpu_precreate() safely under kvm->lock without recrusive lock issue. Suggested-by: Sean Christopherson Signed-off-by: Zeng Guang Message-Id: <20220419154409.11842-1-guang.zeng@intel.com> Signed-off-by: Paolo Bonzini Signed-off-by: Jason Zeng --- arch/s390/kvm/kvm-s390.c | 2 -- arch/x86/kvm/x86.c | 2 +- virt/kvm/kvm_main.c | 10 ++++++---- 3 files changed, 7 insertions(+), 7 deletions(-) diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c index d8e9239c24ff..8b35774d3319 100644 --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -2944,9 +2944,7 @@ static int sca_can_add_vcpu(struct kvm *kvm, unsigned int id) if (!sclp.has_esca || !sclp.has_64bscao) return false; - mutex_lock(&kvm->lock); rc = kvm->arch.use_esca ? 0 : sca_switch_to_extended(kvm); - mutex_unlock(&kvm->lock); return rc == 0 && id < KVM_S390_ESCA_CPU_SLOTS; } diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 033fcb0e11ec..c0d397fcf049 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -9925,7 +9925,7 @@ static void fx_init(struct kvm_vcpu *vcpu) int kvm_arch_vcpu_precreate(struct kvm *kvm, unsigned int id) { - if (kvm_check_tsc_unstable() && atomic_read(&kvm->online_vcpus) != 0) + if (kvm_check_tsc_unstable() && kvm->created_vcpus) pr_warn_once("kvm: SMP vm created on host with unstable TSC; " "guest TSC will not be reliable\n"); diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index a5c107bbf022..93cd86267eba 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -3180,13 +3180,15 @@ static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, u32 id) return -EINVAL; } + r = kvm_arch_vcpu_precreate(kvm, id); + if (r) { + mutex_unlock(&kvm->lock); + return r; + } + kvm->created_vcpus++; mutex_unlock(&kvm->lock); - r = kvm_arch_vcpu_precreate(kvm, id); - if (r) - goto vcpu_decrement; - vcpu = kmem_cache_zalloc(kvm_vcpu_cache, GFP_KERNEL); if (!vcpu) { r = -ENOMEM; -- GitLab