Merge: KVM: arm64: Restore PIRE0_EL1, PIR_EL1 and TCR2_EL1 registers unconditional visibility to userspace

MR: https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-10/-/merge_requests/1005

Upstream Status: RHEL only
JIRA: https://issues.redhat.com/browse/RHEL-89567
Test: successful migration between 10.0 and 10.1

Latest 10.1 rebase broke the migration from older rhel kernels.
This regression was introduced by the following downstream commits:

f1ca81f ("[PATCH v2 2/3] KVM: arm64: Hide TCR2_EL1 from userspace when disabled for guests")
7e64e0b ("[PATCH v2 3/3] KVM: arm64: Hide S1PIE registers from userspace")

which suddently hid three registers, PIRE0_EL1, PIR_EL1 and TCR2_EL1 when the associated
features are not supported by the guest, which is our case. So when doing a migration
from older kernel we try to migrate those 3 regs to a host that does not expose them through
KVM_GET_REG_LIST and qemu fails to migrate.

As this issue breaks all migration testing, we restore the unconditional visibility to
userspace until finding a more elegant solution to this problem that can occur again.
Identifying a clean fix for this will take time and we cannot afford breaking tests
until we get a proper solution upstreamed.

Signed-off-by: Eric Auger <eric.auger@redhat.com>

Approved-by: Sebastian Ott <sebott@redhat.com>
Approved-by: Gavin Shan <gshan@redhat.com>
Approved-by: Cornelia Huck <cohuck@redhat.com>
Approved-by: CKI KWF Bot <cki-ci-bot+kwf-gitlab-com@redhat.com>

Merged-by: CKI GitLab Kmaint Pipeline Bot <26919896-cki-kmaint-pipeline-bot@users.noreply.gitlab.com>

Author: CKI KWF Bot

arch/arm64/kvm/sys_regs.c

@@ -2695,8 +2695,7 @@ static const struct sys_reg_desc sys_reg_descs[] = {
 	{ SYS_DESC(SYS_TTBR0_EL1), access_vm_reg, reset_unknown, TTBR0_EL1 },
 	{ SYS_DESC(SYS_TTBR1_EL1), access_vm_reg, reset_unknown, TTBR1_EL1 },
 	{ SYS_DESC(SYS_TCR_EL1), access_vm_reg, reset_val, TCR_EL1, 0 },
-	{ SYS_DESC(SYS_TCR2_EL1), access_vm_reg, reset_val, TCR2_EL1, 0,
-	  .visibility = tcr2_visibility },
+	{ SYS_DESC(SYS_TCR2_EL1), access_vm_reg, reset_val, TCR2_EL1, 0 },
 
 	PTRAUTH_KEY(APIA),
 	PTRAUTH_KEY(APIB),
@@ -2750,10 +2749,8 @@ static const struct sys_reg_desc sys_reg_descs[] = {
 	{ SYS_DESC(SYS_PMMIR_EL1), trap_raz_wi },
 
 	{ SYS_DESC(SYS_MAIR_EL1), access_vm_reg, reset_unknown, MAIR_EL1 },
-	{ SYS_DESC(SYS_PIRE0_EL1), NULL, reset_unknown, PIRE0_EL1,
-	  .visibility = s1pie_visibility },
-	{ SYS_DESC(SYS_PIR_EL1), NULL, reset_unknown, PIR_EL1,
-	  .visibility = s1pie_visibility },
+	{ SYS_DESC(SYS_PIRE0_EL1), NULL, reset_unknown, PIRE0_EL1 },
+	{ SYS_DESC(SYS_PIR_EL1), NULL, reset_unknown, PIR_EL1 },
 	{ SYS_DESC(SYS_POR_EL1), NULL, reset_unknown, POR_EL1,
 	  .visibility = s1poe_visibility },
 	{ SYS_DESC(SYS_AMAIR_EL1), access_vm_reg, reset_amair_el1, AMAIR_EL1 },