From a621a4e6cb1e249d165f643d511c887c7fc4cdc7 Mon Sep 17 00:00:00 2001 From: Marc Zyngier Date: Fri, 1 Oct 2021 18:05:53 +0100 Subject: [PATCH] UPSTREAM: 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 (cherry picked from commit b6a68b97af23cc75781bed38221ce73144ac2e39) Bug: 204960018 Signed-off-by: Will Deacon Change-Id: Ie796c716fc7cece906a8cded0ae4652a828988bb --- 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 4223a4ba2ea0..3df120878607 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2302,6 +2302,8 @@ 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 b45ae346301a..d276bc897ad9 100644 --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -59,6 +59,7 @@ 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 80fccd599344..67be557a27e2 100644 --- a/arch/arm64/kvm/arm.c +++ b/arch/arm64/kvm/arm.c @@ -2069,6 +2069,11 @@ 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) || @@ -2142,8 +2147,15 @@ 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; }