Re: [PATCH 1/4] KVM: arm64: Ignore 'kvm-arm.mode=protected' when using VHE
From: Mark Rutland <mark.rutland@arm.com>
Date: 2021-06-04 14:03:17
Also in:
kvm, kvmarm
On Thu, Jun 03, 2021 at 07:33:44PM +0100, Will Deacon wrote:
Ignore 'kvm-arm.mode=protected' when using VHE so that kvm_get_mode() only returns KVM_MODE_PROTECTED on systems where the feature is available.
IIUC, since the introduction of the idreg-override code, and the mutate_to_vhe stuff, passing 'kvm-arm.mode=protected' should make the kernel stick to EL1, right? So this should only affect M1 (or other HW with a similar impediment). One minor comment below; otherwise: Acked-by: Mark Rutland <mark.rutland@arm.com>
quoted hunk ↗ jump to hunk
Cc: David Brazdil <redacted> Signed-off-by: Will Deacon <will@kernel.org> --- Documentation/admin-guide/kernel-parameters.txt | 1 - arch/arm64/kernel/cpufeature.c | 10 +--------- arch/arm64/kvm/arm.c | 6 +++++- 3 files changed, 6 insertions(+), 11 deletions(-)diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index cb89dbdedc46..e85dbdf1ee8e 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt@@ -2300,7 +2300,6 @@ protected: nVHE-based mode with support for guests whose state is kept private from the host. - Not valid if the kernel is running in EL2. Defaults to VHE/nVHE based on hardware support.diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index efed2830d141..dc1f2e747828 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c@@ -1773,15 +1773,7 @@ static void cpu_enable_mte(struct arm64_cpu_capabilities const *cap) #ifdef CONFIG_KVM static bool is_kvm_protected_mode(const struct arm64_cpu_capabilities *entry, int __unused) { - if (kvm_get_mode() != KVM_MODE_PROTECTED) - return false; - - if (is_kernel_in_hyp_mode()) { - pr_warn("Protected KVM not available with VHE\n"); - return false; - } - - return true; + return kvm_get_mode() == KVM_MODE_PROTECTED; } #endif /* CONFIG_KVM */diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c index 1cb39c0803a4..8d5e23198dfd 100644 --- a/arch/arm64/kvm/arm.c +++ b/arch/arm64/kvm/arm.c@@ -2121,7 +2121,11 @@ static int __init early_kvm_mode_cfg(char *arg) return -EINVAL; if (strcmp(arg, "protected") == 0) { - kvm_mode = KVM_MODE_PROTECTED; + if (!is_kernel_in_hyp_mode()) + kvm_mode = KVM_MODE_PROTECTED; + else + pr_warn_once("Protected KVM not available with VHE\n");
... assuming this is only for M1, it might be better to say: Protected KVM not available on this hardware ... since that doesn't suggest that other VHE-capable HW is also not PKVM-capable. Thanks, Mark. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel