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KVM: arm64: Allow KVM to be disabled from the command line

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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 <dbrazdil@google.com>
Acked-by: Will Deacon <will@kernel.org>
Acked-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Andrew Scull <ascull@google.com>
Link: https://lore.kernel.org/r/20211001170553.3062988-1-maz@kernel.org
This commit is contained in:
Marc Zyngier 2021-10-01 18:05:53 +01:00
parent 9e1ff307c7
commit b6a68b97af
3 changed files with 16 additions and 1 deletions
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2
Documentation/admin-guide/kernel-parameters.txt
View file

@ -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.

1
arch/arm64/include/asm/kvm_host.h
View file

@ -58,6 +58,7 @@
enum kvm_mode {
KVM_MODE_DEFAULT,
KVM_MODE_PROTECTED,
KVM_MODE_NONE,
};
enum kvm_mode kvm_get_mode(void);

14
arch/arm64/kvm/arm.c
View file

@ -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;
}