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FROMLIST: 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).

Bug: 192819132
Test: boot in EL2, pass kvm-arm.mode=none on cmdline
Link: https://lore.kernel.org/kvmarm/20210903091652.985836-1-maz@kernel.org/
Signed-off-by: Marc Zyngier <maz@kernel.org>
Change-Id: If4d2775b8f1f4119b5f390391f64c65221a17fde
This commit is contained in:
Marc Zyngier
2021-09-03 10:16:52 +01:00
committed by David Brazdil
parent 30d8af3e1e
commit 5b63fb56a8
4 changed files with 18 additions and 1 deletions
Download Patch File Download Diff File Expand all files Collapse all files

3
Documentation/admin-guide/kernel-parameters.txt
View File

@@ -2302,6 +2302,9 @@
kvm-arm.mode=
[KVM,ARM] Select one of KVM/arm64's modes of operation.
none: Forcefully disable KVM and run in nVHE mode,
preventing KVM from ever initialising.
nvhe: Standard nVHE-based mode, without support for
protected guests.

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

@@ -59,6 +59,7 @@
enum kvm_mode {
KVM_MODE_DEFAULT,
KVM_MODE_PROTECTED,
KVM_MODE_NONE,
};
enum kvm_mode kvm_get_mode(void);

1
arch/arm64/kernel/idreg-override.c
View File

@@ -94,6 +94,7 @@ static const struct {
char alias[FTR_ALIAS_NAME_LEN];
char feature[FTR_ALIAS_OPTION_LEN];
} aliases[] __initconst = {
{ "kvm-arm.mode=none", "id_aa64mmfr1.vh=0" },
{ "kvm-arm.mode=nvhe", "id_aa64mmfr1.vh=0" },
{ "kvm-arm.mode=protected", "id_aa64mmfr1.vh=0" },
{ "arm64.nobti", "id_aa64pfr1.bt=0" },

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

@@ -2046,6 +2046,11 @@ 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) ||
@@ -2119,8 +2124,15 @@ 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 && !WARN_ON(is_kernel_in_hyp_mode())) {
kvm_mode = KVM_MODE_NONE;
return 0;
}
return -EINVAL;
}