From: Sean Christopherson Date: Thu, 28 Nov 2024 01:33:40 +0000 (-0800) Subject: KVM: x86: Disallow KVM_CAP_X86_DISABLE_EXITS after vCPU creation X-Git-Tag: v6.14-rc1~94^2~4^2~55 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=04cd8f8628d88da7839b1643db0bef8522c39254;p=thirdparty%2Flinux.git KVM: x86: Disallow KVM_CAP_X86_DISABLE_EXITS after vCPU creation Reject KVM_CAP_X86_DISABLE_EXITS if vCPUs have been created, as disabling PAUSE/MWAIT/HLT exits after vCPUs have been created is broken and useless, e.g. except for PAUSE on SVM, the relevant intercepts aren't updated after vCPU creation. vCPUs may also end up with an inconsistent configuration if exits are disabled between creation of multiple vCPUs. Cc: Hou Wenlong Link: https://lore.kernel.org/all/9227068821b275ac547eb2ede09ec65d2281fe07.1680179693.git.houwenlong.hwl@antgroup.com Link: https://lore.kernel.org/all/20230121020738.2973-2-kechenl@nvidia.com Reviewed-by: Maxim Levitsky Reviewed-by: Xiaoyao Li Reviewed-by: Binbin Wu Link: https://lore.kernel.org/r/20241128013424.4096668-14-seanjc@google.com Signed-off-by: Sean Christopherson --- diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index 454c2aaa155e5..bbe445e6c1132 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -7670,6 +7670,7 @@ branch to guests' 0x200 interrupt vector. :Architectures: x86 :Parameters: args[0] defines which exits are disabled :Returns: 0 on success, -EINVAL when args[0] contains invalid exits + or if any vCPUs have already been created Valid bits in args[0] are:: diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 503bfcbc1735a..e3c3ceb549660 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -6531,6 +6531,10 @@ split_irqchip_unlock: if (cap->args[0] & ~KVM_X86_DISABLE_VALID_EXITS) break; + mutex_lock(&kvm->lock); + if (kvm->created_vcpus) + goto disable_exits_unlock; + if (cap->args[0] & KVM_X86_DISABLE_EXITS_PAUSE) kvm->arch.pause_in_guest = true; @@ -6552,6 +6556,8 @@ split_irqchip_unlock: } r = 0; +disable_exits_unlock: + mutex_unlock(&kvm->lock); break; case KVM_CAP_MSR_PLATFORM_INFO: kvm->arch.guest_can_read_msr_platform_info = cap->args[0];