[PATCH v3 1/2] KVM: arm64: Allow userspace to change ID_AA64PFR1_EL1

[Shaoqin Huang]

Allow userspace to change the guest-visible value of the register with
some severe limitation:

  - No changes to features not virtualized by KVM (MPAM_frac, RAS_frac,
    SME, RNDP_trap).

  - No changes to features (CSV2_frac, NMI, MTE_frac, GCS, THE, MTEX,
    DF2, PFAR) which haven't been added into the ftr_id_aa64pfr1[].
    Because the struct arm64_ftr_bits definition for each feature in the
    ftr_id_aa64pfr1[] is used by arm64_check_features. If they're not
    existing in the ftr_id_aa64pfr1[], the for loop won't check the if
    the new_val is safe for those features.
---
 arch/arm64/kvm/sys_regs.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 22b45a15d068..159cded22357 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -2306,7 +2306,9 @@ static const struct sys_reg_desc sys_reg_descs[] = {
 		   ID_AA64PFR0_EL1_GIC |
 		   ID_AA64PFR0_EL1_AdvSIMD |
 		   ID_AA64PFR0_EL1_FP), },
-	ID_SANITISED(ID_AA64PFR1_EL1),
+	ID_WRITABLE(ID_AA64PFR1_EL1, ID_AA64PFR1_EL1_MTE |
+				     ID_AA64PFR1_EL1_SSBS |
+				     ID_AA64PFR1_EL1_BT),
 	ID_UNALLOCATED(4,2),
 	ID_UNALLOCATED(4,3),
 	ID_WRITABLE(ID_AA64ZFR0_EL1, ~ID_AA64ZFR0_EL1_RES0),
-- 
2.40.1