Re: [PATCH 3/4] KVM: arm64: Enforce reserved bits for PSCI target affinities
From: Marc Zyngier <maz@kernel.org>
Date: 2021-08-18 11:13:04
Also in:
kvmarm
On Wed, 18 Aug 2021 09:50:46 +0100, Oliver Upton [off-list ref] 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").
quoted hunk ↗ jump to hunk
Return INVALID_PARAMETERS if the guest incorrectly sets a reserved bit. Signed-off-by: Oliver Upton <redacted> --- 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);
quoted hunk ↗ jump to hunk
+} + 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.