KVM: arm64: show writable masks for feature registers

Instead of using ~0UL provide the actual writable mask for
non-id feature registers in the output of the
KVM_ARM_GET_REG_WRITABLE_MASKS ioctl.

This changes the mask for the CTR_EL0 and CLIDR_EL1 registers.

Signed-off-by: Sebastian Ott <sebott@redhat.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Link: https://lore.kernel.org/r/20240619174036.483943-9-oliver.upton@linux.dev
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>

diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index a12f3bdfb43d279a0eda6ba80095fe5d511ac25e..d8d2a7880576fb1f3f88b49d579bcef95241234d 100644 (file)
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -2486,7 +2486,7 @@ static const struct sys_reg_desc sys_reg_descs[] = {
 
        { SYS_DESC(SYS_CCSIDR_EL1), access_ccsidr },
        { SYS_DESC(SYS_CLIDR_EL1), access_clidr, reset_clidr, CLIDR_EL1,
-         .set_user = set_clidr },
+         .set_user = set_clidr, .val = ~CLIDR_EL1_RES0 },
        { SYS_DESC(SYS_CCSIDR2_EL1), undef_access },
        { SYS_DESC(SYS_SMIDR_EL1), undef_access },
        { SYS_DESC(SYS_CSSELR_EL1), access_csselr, reset_unknown, CSSELR_EL1 },
@@ -4046,20 +4046,11 @@ int kvm_vm_ioctl_get_reg_writable_masks(struct kvm *kvm, struct reg_mask_range *
                if (!is_feature_id_reg(encoding) || !reg->set_user)
                        continue;
 
-               /*
-                * For ID registers, we return the writable mask. Other feature
-                * registers return a full 64bit mask. That's not necessary
-                * compliant with a given revision of the architecture, but the
-                * RES0/RES1 definitions allow us to do that.
-                */
-               if (is_vm_ftr_id_reg(encoding)) {
-                       if (!reg->val ||
-                           (is_aa32_id_reg(encoding) && !kvm_supports_32bit_el0()))
-                               continue;
-                       val = reg->val;
-               } else {
-                       val = ~0UL;
+               if (!reg->val ||
+                   (is_aa32_id_reg(encoding) && !kvm_supports_32bit_el0())) {
+                       continue;
                }
+               val = reg->val;
 
                if (put_user(val, (masks + KVM_ARM_FEATURE_ID_RANGE_INDEX(encoding))))
                        return -EFAULT;