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UPSTREAM: 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
(cherry picked from commit b6a68b97af23cc75781bed38221ce73144ac2e39)
Bug: 204960018
Signed-off-by: Will Deacon <willdeacon@google.com>
Change-Id: Ie796c716fc7cece906a8cded0ae4652a828988bb
(cherry picked from commit a621a4e6cb1e249d165f643d511c887c7fc4cdc7)
This commit is contained in:
Marc Zyngier
2021-10-01 18:05:53 +01:00
committed by Treehugger Robot
parent 631630d75f
commit dbcd8cb535
3 changed files with 16 additions and 1 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
Documentation/admin-guide/kernel-parameters.txt
View File

@@ -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.

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

@@ -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;
}