* [PATCH v2] KVM: arm64: Allow KVM to be disabled from the command line
@ 2021-10-01 17:05 Marc Zyngier
2021-10-07 16:59 ` Andrew Scull
2021-10-11 9:18 ` Marc Zyngier
0 siblings, 2 replies; 3+ messages in thread
From: Marc Zyngier @ 2021-10-01 17:05 UTC (permalink / raw)
To: kvmarm, kvm, linux-arm-kernel
Cc: James Morse, Suzuki K Poulose, Alexandru Elisei, kernel-team,
David Brazdil, Will Deacon
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>
---
Notes:
v2: Dropped the id_aa64mmfr1_vh=0 setting so that KVM can be disabled
and yet stay in VHE mode on platforms that require it.
I kept the AB/RB's, but please shout if you disagree!
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 91ba391f9b32..f268731a3d4d 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -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.
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index f8be56d5342b..019490c67976 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 fe102cd2e518..658171231af9 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -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;
}
--
2.30.2
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH v2] KVM: arm64: Allow KVM to be disabled from the command line
2021-10-01 17:05 [PATCH v2] KVM: arm64: Allow KVM to be disabled from the command line Marc Zyngier
@ 2021-10-07 16:59 ` Andrew Scull
2021-10-11 9:18 ` Marc Zyngier
1 sibling, 0 replies; 3+ messages in thread
From: Andrew Scull @ 2021-10-07 16:59 UTC (permalink / raw)
To: Marc Zyngier
Cc: kvmarm, kvm, linux-arm-kernel, James Morse, Suzuki K Poulose,
Alexandru Elisei, kernel-team, David Brazdil, Will Deacon
Reviewed-by: Andrew Scull <ascull@google.com>
On Fri, 1 Oct 2021 at 18:06, Marc Zyngier <maz@kernel.org> wrote:
>
> 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>
> ---
>
> Notes:
> v2: Dropped the id_aa64mmfr1_vh=0 setting so that KVM can be disabled
> and yet stay in VHE mode on platforms that require it.
> I kept the AB/RB's, but please shout if you disagree!
>
> 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 91ba391f9b32..f268731a3d4d 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -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.
>
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index f8be56d5342b..019490c67976 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 fe102cd2e518..658171231af9 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -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;
> }
> --
> 2.30.2
>
> --
> To unsubscribe from this group and stop receiving emails from it, send an email to kernel-team+unsubscribe@android.com.
>
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH v2] KVM: arm64: Allow KVM to be disabled from the command line
2021-10-01 17:05 [PATCH v2] KVM: arm64: Allow KVM to be disabled from the command line Marc Zyngier
2021-10-07 16:59 ` Andrew Scull
@ 2021-10-11 9:18 ` Marc Zyngier
1 sibling, 0 replies; 3+ messages in thread
From: Marc Zyngier @ 2021-10-11 9:18 UTC (permalink / raw)
To: linux-arm-kernel, Marc Zyngier, kvmarm, kvm
Cc: Alexandru Elisei, Will Deacon, David Brazdil, Suzuki K Poulose,
kernel-team, James Morse
On Fri, 1 Oct 2021 18:05:53 +0100, Marc Zyngier wrote:
> 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).
Applied to next, thanks!
[1/1] KVM: arm64: Allow KVM to be disabled from the command line
commit: b6a68b97af23cc75781bed38221ce73144ac2e39
Cheers,
M.
--
Without deviation from the norm, progress is not possible.
^ permalink raw reply [flat|nested] 3+ messages in thread
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