[PATCH 3/3] arm64: cpufeature: upgrade hyp caps to final

[Mark Rutland]

We finalize caps before initializing kvm hyp code, and any use of
cpus_have_const_cap() in kvm hyp code generates redundant and
potentially unsound code to read the cpu_hwcaps array.

A number of helper functions used in both hyp context and regular kernel
context use cpus_have_const_cap(), as some regular kernel code runs
before the capabilities are finalized. It's tedious and error-prone to
write separate copies of these for hyp and non-hyp code.

So that we can avoid the redundant code, let's automatically upgrade
cpus_have_const_cap() to cpus_have_final_cap() when used in hyp context.
With this change, there's never a reason to access to cpu_hwcaps array
from hyp code, and we don't need to create an NVHE alias for this.

This should have no effect on non-hyp code.

Signed-off-by: Mark Rutland <mark.rutland at arm.com>
Cc: David Brazdil <dbrazdil at google.com>
Cc: Marc Zyngier <maz at kernel.org>
Cc: Will Deacon <will at kernel.org>
---
 arch/arm64/include/asm/cpufeature.h | 26 ++++++++++++++++++++++++--
 arch/arm64/include/asm/virt.h       | 12 ------------
 arch/arm64/kernel/image-vars.h      |  1 -
 3 files changed, 24 insertions(+), 15 deletions(-)

diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index 9f671aa0419b7..79d6a0371c78a 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -375,6 +375,23 @@ cpucap_multi_entry_cap_matches(const struct arm64_cpu_capabilities *entry,
 	return false;
 }
 
+static __always_inline bool is_vhe_hyp_code(void)
+{
+	/* Only defined for code run in VHE hyp context */
+	return __is_defined(__KVM_VHE_HYPERVISOR__);
+}
+
+static __always_inline bool is_nvhe_hyp_code(void)
+{
+	/* Only defined for code run in NVHE hyp context */
+	return __is_defined(__KVM_NVHE_HYPERVISOR__);
+}
+
+static __always_inline bool is_hyp_code(void)
+{
+	return is_vhe_hyp_code() || is_nvhe_hyp_code();
+}
+
 extern DECLARE_BITMAP(cpu_hwcaps, ARM64_NCAPS);
 extern struct static_key_false cpu_hwcap_keys[ARM64_NCAPS];
 extern struct static_key_false arm64_const_caps_ready;
@@ -444,8 +461,11 @@ static __always_inline bool cpus_have_final_cap(int num)
 }
 
 /*
- * Test for a capability, possibly with a runtime check.
+ * Test for a capability, possibly with a runtime check for non-hyp code.
  *
+ * For hyp code, this behaves the same as cpus_have_final_cap().
+ *
+ * For non-hyp code:
  * Before capabilities are finalized, this behaves as cpus_have_cap().
  * After capabilities are finalized, this is patched to avoid a runtime check.
  *
@@ -453,7 +473,9 @@ static __always_inline bool cpus_have_final_cap(int num)
  */
 static __always_inline bool cpus_have_const_cap(int num)
 {
-	if (system_capabilities_finalized())
+	if (is_hyp_code())
+		return cpus_have_final_cap(num);
+	else if (system_capabilities_finalized())
 		return __cpus_have_const_cap(num);
 	else
 		return cpus_have_cap(num);
diff --git a/arch/arm64/include/asm/virt.h b/arch/arm64/include/asm/virt.h
index 300be14ba77b2..6069be50baf9f 100644
--- a/arch/arm64/include/asm/virt.h
+++ b/arch/arm64/include/asm/virt.h
@@ -83,18 +83,6 @@ static inline bool is_kernel_in_hyp_mode(void)
 	return read_sysreg(CurrentEL) == CurrentEL_EL2;
 }
 
-static __always_inline bool is_vhe_hyp_code(void)
-{
-	/* Only defined for code run in VHE hyp context */
-	return __is_defined(__KVM_VHE_HYPERVISOR__);
-}
-
-static __always_inline bool is_nvhe_hyp_code(void)
-{
-	/* Only defined for code run in NVHE hyp context */
-	return __is_defined(__KVM_NVHE_HYPERVISOR__);
-}
-
 static __always_inline bool has_vhe(void)
 {
 	/*
diff --git a/arch/arm64/kernel/image-vars.h b/arch/arm64/kernel/image-vars.h
index fbd4b6b1fde5d..ad8432251733e 100644
--- a/arch/arm64/kernel/image-vars.h
+++ b/arch/arm64/kernel/image-vars.h
@@ -87,7 +87,6 @@ KVM_NVHE_ALIAS(__icache_flags);
 /* Kernel symbols needed for cpus_have_final/const_caps checks. */
 KVM_NVHE_ALIAS(arm64_const_caps_ready);
 KVM_NVHE_ALIAS(cpu_hwcap_keys);
-KVM_NVHE_ALIAS(cpu_hwcaps);
 
 /* Static keys which are set if a vGIC trap should be handled in hyp. */
 KVM_NVHE_ALIAS(vgic_v2_cpuif_trap);
-- 
2.11.0