From b6a68b97af23cc75781bed38221ce73144ac2e39 Mon Sep 17 00:00:00 2001 From: Marc Zyngier Date: Fri, 1 Oct 2021 18:05:53 +0100 Subject: [PATCH] KVM: arm64: Allow KVM to be disabled from the command line Although KVM can be compiled out of the kernel, it cannot be disabled at runtime. Allow this possibility by introducing a new mode that will prevent KVM from initialising. This is useful in the (limited) circumstances where you don't want KVM to be available (what is wrong with you?), or when you want to install another hypervisor instead (good luck with that). Reviewed-by: David Brazdil Acked-by: Will Deacon Acked-by: Suzuki K Poulose Signed-off-by: Marc Zyngier Reviewed-by: Andrew Scull Link: https://lore.kernel.org/r/20211001170553.3062988-1-maz@kernel.org --- Documentation/admin-guide/kernel-parameters.txt | 2 ++ arch/arm64/include/asm/kvm_host.h | 1 + arch/arm64/kvm/arm.c | 14 +++++++++++++- 3 files changed, 16 insertions(+), 1 deletion(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 91ba391f9b32..f268731a3d4d 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2365,6 +2365,8 @@ kvm-arm.mode= [KVM,ARM] Select one of KVM/arm64's modes of operation. + none: Forcefully disable KVM. + nvhe: Standard nVHE-based mode, without support for protected guests. diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h index f8be56d5342b..019490c67976 100644 --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -58,6 +58,7 @@ enum kvm_mode { KVM_MODE_DEFAULT, KVM_MODE_PROTECTED, + KVM_MODE_NONE, }; enum kvm_mode kvm_get_mode(void); diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c index fe102cd2e518..658171231af9 100644 --- a/arch/arm64/kvm/arm.c +++ b/arch/arm64/kvm/arm.c @@ -2064,6 +2064,11 @@ int kvm_arch_init(void *opaque) return -ENODEV; } + if (kvm_get_mode() == KVM_MODE_NONE) { + kvm_info("KVM disabled from command line\n"); + return -ENODEV; + } + in_hyp_mode = is_kernel_in_hyp_mode(); if (cpus_have_final_cap(ARM64_WORKAROUND_DEVICE_LOAD_ACQUIRE) || @@ -2137,8 +2142,15 @@ static int __init early_kvm_mode_cfg(char *arg) return 0; } - if (strcmp(arg, "nvhe") == 0 && !WARN_ON(is_kernel_in_hyp_mode())) + if (strcmp(arg, "nvhe") == 0 && !WARN_ON(is_kernel_in_hyp_mode())) { + kvm_mode = KVM_MODE_DEFAULT; return 0; + } + + if (strcmp(arg, "none") == 0) { + kvm_mode = KVM_MODE_NONE; + return 0; + } return -EINVAL; }