[PATCH 1/2] KVM: arm64: Initialise TCR2_EL2 for nVHE mode

[Mark Brown]

We currently only configure TCR2_EL2 in VHE mode, this is done in
__finalise_el2 which only runs for VHE. While all systems with TCR2_EL2
should have VHE support users may wish to run them in nVHE mode, for
example in order to use protected VMs.

Determine the value to load for TCR2_EL2 in C code in a similar manner to
TCR_EL2, further patches will configure some bits in the register. When
resetting back to the hypervisor stub clear all bits in the register in
case something without support for TCR2_EL2 runs later.

The only practical impact should be if we are started with a misconfigured
TCR2_EL2.

Signed-off-by: Mark Brown <broonie@xxxxxxxxxx>
---
 arch/arm64/include/asm/kvm_asm.h   |  1 +
 arch/arm64/kernel/asm-offsets.c    |  1 +
 arch/arm64/kvm/arm.c               |  5 ++++-
 arch/arm64/kvm/hyp/nvhe/hyp-init.S | 18 ++++++++++++++++--
 4 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h
index e5b92ac09e69..eb796436d6eb 100644
--- a/arch/arm64/include/asm/kvm_asm.h
+++ b/arch/arm64/include/asm/kvm_asm.h
@@ -208,6 +208,7 @@ extern void *__vhe_undefined_symbol;
 struct kvm_nvhe_init_params {
 	unsigned long mair_el2;
 	unsigned long tcr_el2;
+	unsigned long tcr2_el2;
 	unsigned long tpidr_el2;
 	unsigned long stack_hyp_va;
 	unsigned long stack_pa;
diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
index 9c853ed3ceab..baffe58015d6 100644
--- a/arch/arm64/kernel/asm-offsets.c
+++ b/arch/arm64/kernel/asm-offsets.c
@@ -118,6 +118,7 @@ int main(void)
   DEFINE(HOST_DATA_CONTEXT,	offsetof(struct kvm_host_data, host_ctxt));
   DEFINE(NVHE_INIT_MAIR_EL2,	offsetof(struct kvm_nvhe_init_params, mair_el2));
   DEFINE(NVHE_INIT_TCR_EL2,	offsetof(struct kvm_nvhe_init_params, tcr_el2));
+  DEFINE(NVHE_INIT_TCR2_EL2,	offsetof(struct kvm_nvhe_init_params, tcr2_el2));
   DEFINE(NVHE_INIT_TPIDR_EL2,	offsetof(struct kvm_nvhe_init_params, tpidr_el2));
   DEFINE(NVHE_INIT_STACK_HYP_VA,	offsetof(struct kvm_nvhe_init_params, stack_hyp_va));
   DEFINE(NVHE_INIT_PGD_PA,	offsetof(struct kvm_nvhe_init_params, pgd_pa));
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 8b080804bc90..88eb0459ad4b 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -2158,7 +2158,7 @@ static int kvm_init_vector_slots(void)
 static void __init cpu_prepare_hyp_mode(int cpu, u32 hyp_va_bits)
 {
 	struct kvm_nvhe_init_params *params = per_cpu_ptr_nvhe_sym(kvm_init_params, cpu);
-	unsigned long tcr;
+	unsigned long tcr, tcr2;
 
 	/*
 	 * Calculate the raw per-cpu offset without a translation from the
@@ -2186,6 +2186,9 @@ static void __init cpu_prepare_hyp_mode(int cpu, u32 hyp_va_bits)
 	tcr |= TCR_T0SZ(hyp_va_bits);
 	params->tcr_el2 = tcr;
 
+	tcr2 = 0;
+	params->tcr2_el2 = tcr2;
+
 	params->pgd_pa = kvm_mmu_get_httbr();
 	if (is_protected_kvm_enabled())
 		params->hcr_el2 = HCR_HOST_NVHE_PROTECTED_FLAGS;
diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-init.S b/arch/arm64/kvm/hyp/nvhe/hyp-init.S
index 0b3e0b28dfc7..a39de9c20d27 100644
--- a/arch/arm64/kvm/hyp/nvhe/hyp-init.S
+++ b/arch/arm64/kvm/hyp/nvhe/hyp-init.S
@@ -137,8 +137,13 @@ alternative_if ARM64_HAS_CNP
 alternative_else_nop_endif
 	msr	ttbr0_el2, x2
 
-	ldr	x0, [x0, #NVHE_INIT_TCR_EL2]
-	msr	tcr_el2, x0
+	ldr	x1, [x0, #NVHE_INIT_TCR_EL2]
+	msr	tcr_el2, x1
+
+alternative_if ARM64_HAS_TCR2
+	ldr	x1, [x0, #NVHE_INIT_TCR2_EL2]
+	msr	REG_TCR2_EL2, x1
+alternative_else_nop_endif
 
 	isb
 
@@ -250,6 +255,15 @@ reset:
 	mov_q	x5, INIT_SCTLR_EL2_MMU_OFF
 	pre_disable_mmu_workaround
 	msr	sctlr_el2, x5
+
+alternative_if ARM64_HAS_TCR2
+	/*
+	 * Disable any features we enabled in case the next user doesn't
+	 * have TCR2_EL2 support.
+	 */
+	msr	REG_TCR2_EL2, xzr
+alternative_else_nop_endif
+
 	isb
 
 	/* Install stub vectors */

-- 
2.47.3