diff options
| author | Oliver Upton <oliver.upton@linux.dev> | 2025-09-18 09:55:05 -0700 |
|---|---|---|
| committer | Marc Zyngier <maz@kernel.org> | 2025-09-19 10:52:01 +0100 |
| commit | 5aea4096380f5b14e3c0345bdafc291e9ae6d8d1 (patch) | |
| tree | d1ebf907ab2a3f46aea8ed8fbbd5589a626686b2 | |
| parent | ff37a41db8b47834b747b3bb427825fc75bc86a7 (diff) | |
KVM: arm64: nv: Allow userspace to de-feature stage-2 TGRANs
KVM advertises the stage-2 TGRAN fields as writable to userspace but
prevents any modification for NV-enabled VMs. Update the special-cased
sanitization to permit de-featuring a particular TGRAN without allowing
the legacy value which refers to the stage-1 field for support.
Reported-by: Itaru Kitayama <itaru.kitayama@linux.dev>
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
| -rw-r--r-- | arch/arm64/kvm/sys_regs.c | 23 |
1 files changed, 18 insertions, 5 deletions
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c index b29f72478a50..83ecfdb46704 100644 --- a/arch/arm64/kvm/sys_regs.c +++ b/arch/arm64/kvm/sys_regs.c @@ -2148,16 +2148,29 @@ static int set_id_aa64pfr1_el1(struct kvm_vcpu *vcpu, return set_id_reg(vcpu, rd, user_val); } +/* + * Allow userspace to de-feature a stage-2 translation granule but prevent it + * from claiming the impossible. + */ +#define tgran2_val_allowed(tg, safe, user) \ +({ \ + u8 __s = SYS_FIELD_GET(ID_AA64MMFR0_EL1, tg, safe); \ + u8 __u = SYS_FIELD_GET(ID_AA64MMFR0_EL1, tg, user); \ + \ + __s == __u || __u == ID_AA64MMFR0_EL1_##tg##_NI; \ +}) + static int set_id_aa64mmfr0_el1(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd, u64 user_val) { u64 sanitized_val = kvm_read_sanitised_id_reg(vcpu, rd); - u64 tgran2_mask = ID_AA64MMFR0_EL1_TGRAN4_2_MASK | - ID_AA64MMFR0_EL1_TGRAN16_2_MASK | - ID_AA64MMFR0_EL1_TGRAN64_2_MASK; - if (vcpu_has_nv(vcpu) && - ((sanitized_val & tgran2_mask) != (user_val & tgran2_mask))) + if (!vcpu_has_nv(vcpu)) + return set_id_reg(vcpu, rd, user_val); + + if (!tgran2_val_allowed(TGRAN4_2, sanitized_val, user_val) || + !tgran2_val_allowed(TGRAN16_2, sanitized_val, user_val) || + !tgran2_val_allowed(TGRAN64_2, sanitized_val, user_val)) return -EINVAL; return set_id_reg(vcpu, rd, user_val); |