From dbcd8cb5350ea104c3d775164810a668fa61a07a 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 (cherry picked from commit a621a4e6cb1e249d165f643d511c887c7fc4cdc7) --- 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 c841b5208771..3a16cdd1e251 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2311,6 +2311,8 @@ 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 b7fa62950b78..b714f048481c 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 78550c856c24..20974e71c9a6 100644 --- a/arch/arm64/kvm/arm.c +++ b/arch/arm64/kvm/arm.c @@ -2061,6 +2061,11 @@ 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; }