| Message ID | 20210603183347.1695-2-will@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | kvm/arm64: Initial pKVM user ABI | expand |
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> > > Cc: David Brazdil <dbrazdil@google.com> > 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.
On Fri, Jun 04, 2021 at 03:01:17PM +0100, Mark Rutland wrote: > 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). It's not just about the M1, unfortunately. You can boot with: "kvm-arm.mode=protected id_aa64mmfr1.vh=1" which will force VHE mode, so we should fail protected mode in that case. > One minor comment below; otherwise: > > Acked-by: Mark Rutland <mark.rutland@arm.com> Thanks, I'll keep the tag but please yell if you want me to drop it. > > 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. I'm just moving the existing string here, but as above, it's not M1 specific. Will
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"); + return 0; }
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. Cc: David Brazdil <dbrazdil@google.com> 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(-)