On Wed, 18 Aug 2021 09:50:46 +0100,
Oliver Upton <oupton@xxxxxxxxxx> wrote:
>
> Some calls in PSCI take a target affinity argument, defined to be
> bit-compatible with the affinity fields in MPIDR_EL1. All other bits in
> the parameter are reserved and must be 0.
For future reference, it may be worth quoting the spec (ARM DEN 0022D,
5.1.4 "CPU_ON").
> Return INVALID_PARAMETERS if the guest incorrectly sets a reserved
> bit.
>
> Signed-off-by: Oliver Upton <oupton@xxxxxxxxxx>
> ---
> arch/arm64/kvm/psci.c | 20 +++++++++++++++++---
> 1 file changed, 17 insertions(+), 3 deletions(-)
>
> diff --git a/arch/arm64/kvm/psci.c b/arch/arm64/kvm/psci.c
> index db4056ecccfd..bb76be01abd2 100644
> --- a/arch/arm64/kvm/psci.c
> +++ b/arch/arm64/kvm/psci.c
> @@ -59,6 +59,17 @@ static void kvm_psci_vcpu_off(struct kvm_vcpu *vcpu)
> kvm_vcpu_kick(vcpu);
> }
>
> +static inline bool kvm_psci_valid_affinity(struct kvm_vcpu *vcpu,
> + unsigned long affinity)
> +{
> + unsigned long mask = MPIDR_HWID_BITMASK;
> +
> + if (vcpu_mode_is_32bit(vcpu))
> + mask &= ~((u32) 0);
I don't think we need this anymore since 5.7:
- fdc9999e20cd ("KVM: arm64: PSCI: Forbid 64bit functions for 32bit
guests") guarantees that the guest can't trick KVM into using the
SMC64 functions.
- with 2890ac993daa ("KVM: arm64: PSCI: Narrow input registers when
using 32bit functions"), the registers are always narrowed down to
32bit
Put the two together, and you can't have a 32bit guest issuing a PSCI
operation with crap in the upper 32bits.
> +
> + return !(affinity & ~mask);
So the whole helper can now be rewritten as
return !(affinity & ~MPIDR_HWID_BITMASK);
> +}
> +
> static unsigned long kvm_psci_vcpu_on(struct kvm_vcpu *source_vcpu)
> {
> struct vcpu_reset_state *reset_state;
> @@ -66,9 +77,9 @@ static unsigned long kvm_psci_vcpu_on(struct kvm_vcpu *source_vcpu)
> struct kvm_vcpu *vcpu = NULL;
> unsigned long cpu_id;
>
> - cpu_id = smccc_get_arg1(source_vcpu) & MPIDR_HWID_BITMASK;
> - if (vcpu_mode_is_32bit(source_vcpu))
> - cpu_id &= ~((u32) 0);
> + cpu_id = smccc_get_arg1(source_vcpu);
> + if (!kvm_psci_valid_affinity(source_vcpu, cpu_id))
> + return PSCI_RET_INVALID_PARAMS;
>
> vcpu = kvm_mpidr_to_vcpu(kvm, cpu_id);
>
> @@ -126,6 +137,9 @@ static unsigned long kvm_psci_vcpu_affinity_info(struct kvm_vcpu *vcpu)
> target_affinity = smccc_get_arg1(vcpu);
> lowest_affinity_level = smccc_get_arg2(vcpu);
>
> + if (!kvm_psci_valid_affinity(vcpu, target_affinity))
> + return PSCI_RET_INVALID_PARAMS;
> +
> /* Determine target affinity mask */
> target_affinity_mask = psci_affinity_mask(lowest_affinity_level);
> if (!target_affinity_mask)
Otherwise, looks good to me.
Thanks,
M.
--
Without deviation from the norm, progress is not possible.
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