[PATCH v4 09/38] arm64: kvm: Use cpus_have_final_cap() explicitly

From: Mark Rutland <mark.rutland@arm.com>
To: linux-arm-kernel@lists.infradead.org
Cc: ardb@kernel.org, bertrand.marquis@arm.com,
	boris.ostrovsky@oracle.com, broonie@kernel.org,
	catalin.marinas@arm.com, daniel.lezcano@linaro.org,
	james.morse@arm.com, jgross@suse.com, kristina.martsenko@arm.com,
	mark.rutland@arm.com, maz@kernel.org, oliver.upton@linux.dev,
	pcc@google.com, sstabellini@kernel.org, suzuki.poulose@arm.com,
	tglx@linutronix.de, vladimir.murzin@arm.com, will@kernel.org
Subject: [PATCH v4 09/38] arm64: kvm: Use cpus_have_final_cap() explicitly
Date: Mon, 16 Oct 2023 11:24:32 +0100	[thread overview]
Message-ID: <20231016102501.3643901-10-mark.rutland@arm.com> (raw)
In-Reply-To: <20231016102501.3643901-1-mark.rutland@arm.com>

Much of the arm64 KVM code uses cpus_have_const_cap() to check for
cpucaps, but this is unnecessary and it would be preferable to use
cpus_have_final_cap().

For historical reasons, cpus_have_const_cap() is more complicated than
it needs to be. Before cpucaps are finalized, it will perform a bitmap
test of the system_cpucaps bitmap, and once cpucaps are finalized it
will use an alternative branch. This used to be necessary to handle some
race conditions in the window between cpucap detection and the
subsequent patching of alternatives and static branches, where different
branches could be out-of-sync with one another (or w.r.t. alternative
sequences). Now that we use alternative branches instead of static
branches, these are all patched atomically w.r.t. one another, and there
are only a handful of cases that need special care in the window between
cpucap detection and alternative patching.

Due to the above, it would be nice to remove cpus_have_const_cap(), and
migrate callers over to alternative_has_cap_*(), cpus_have_final_cap(),
or cpus_have_cap() depending on when their requirements. This will
remove redundant instructions and improve code generation, and will make
it easier to determine how each callsite will behave before, during, and
after alternative patching.

KVM is initialized after cpucaps have been finalized and alternatives
have been patched. Since commit:

  d86de40decaa14e6 ("arm64: cpufeature: upgrade hyp caps to final")

... use of cpus_have_const_cap() in hyp code is automatically converted
to use cpus_have_final_cap():

| static __always_inline bool cpus_have_const_cap(int num)
| {
| 	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);
| }

Thus, converting hyp code to use cpus_have_final_cap() directly will not
result in any functional change.

Non-hyp KVM code is also not executed until cpucaps have been finalized,
and it would be preferable to extent the same treatment to this code and
use cpus_have_final_cap() directly.

This patch converts instances of cpus_have_const_cap() in KVM-only code
over to cpus_have_final_cap(). As all of this code runs after cpucaps
have been finalized, there should be no functional change as a result of
this patch, but the redundant instructions generated by
cpus_have_const_cap() will be removed from the non-hyp KVM code.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Marc Zyngier <maz@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Oliver Upton <oliver.upton@linux.dev>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: Will Deacon <will@kernel.org>
---
 arch/arm64/include/asm/kvm_emulate.h |  4 ++--
 arch/arm64/include/asm/kvm_host.h    |  2 +-
 arch/arm64/include/asm/kvm_mmu.h     |  2 +-
 arch/arm64/kvm/arm.c                 | 10 +++++-----
 arch/arm64/kvm/guest.c               |  4 ++--
 arch/arm64/kvm/hyp/pgtable.c         |  2 +-
 arch/arm64/kvm/mmu.c                 |  2 +-
 arch/arm64/kvm/sys_regs.c            |  2 +-
 arch/arm64/kvm/vgic/vgic-v3.c        |  2 +-
 9 files changed, 15 insertions(+), 15 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
index 3d6725ff0bf6d..cbd2f163a67d2 100644
--- a/arch/arm64/include/asm/kvm_emulate.h
+++ b/arch/arm64/include/asm/kvm_emulate.h
@@ -71,14 +71,14 @@ static inline void vcpu_reset_hcr(struct kvm_vcpu *vcpu)
 	vcpu->arch.hcr_el2 = HCR_GUEST_FLAGS;
 	if (has_vhe() || has_hvhe())
 		vcpu->arch.hcr_el2 |= HCR_E2H;
-	if (cpus_have_const_cap(ARM64_HAS_RAS_EXTN)) {
+	if (cpus_have_final_cap(ARM64_HAS_RAS_EXTN)) {
 		/* route synchronous external abort exceptions to EL2 */
 		vcpu->arch.hcr_el2 |= HCR_TEA;
 		/* trap error record accesses */
 		vcpu->arch.hcr_el2 |= HCR_TERR;
 	}
 
-	if (cpus_have_const_cap(ARM64_HAS_STAGE2_FWB)) {
+	if (cpus_have_final_cap(ARM64_HAS_STAGE2_FWB)) {
 		vcpu->arch.hcr_el2 |= HCR_FWB;
 	} else {
 		/*
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index af06ccb7ee343..e64d64e6ad449 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -1052,7 +1052,7 @@ static inline void kvm_init_host_cpu_context(struct kvm_cpu_context *cpu_ctxt)
 
 static inline bool kvm_system_needs_idmapped_vectors(void)
 {
-	return cpus_have_const_cap(ARM64_SPECTRE_V3A);
+	return cpus_have_final_cap(ARM64_SPECTRE_V3A);
 }
 
 static inline void kvm_arch_sync_events(struct kvm *kvm) {}
diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
index 96a80e8f62263..27810667dec7d 100644
--- a/arch/arm64/include/asm/kvm_mmu.h
+++ b/arch/arm64/include/asm/kvm_mmu.h
@@ -218,7 +218,7 @@ static inline void __clean_dcache_guest_page(void *va, size_t size)
 	 * faulting in pages. Furthermore, FWB implies IDC, so cleaning to
 	 * PoU is not required either in this case.
 	 */
-	if (cpus_have_const_cap(ARM64_HAS_STAGE2_FWB))
+	if (cpus_have_final_cap(ARM64_HAS_STAGE2_FWB))
 		return;
 
 	kvm_flush_dcache_to_poc(va, size);
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 4866b3f7b4ea3..4ea6c22250a51 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -284,7 +284,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 		r = kvm_arm_pvtime_supported();
 		break;
 	case KVM_CAP_ARM_EL1_32BIT:
-		r = cpus_have_const_cap(ARM64_HAS_32BIT_EL1);
+		r = cpus_have_final_cap(ARM64_HAS_32BIT_EL1);
 		break;
 	case KVM_CAP_GUEST_DEBUG_HW_BPS:
 		r = get_num_brps();
@@ -296,7 +296,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 		r = kvm_arm_support_pmu_v3();
 		break;
 	case KVM_CAP_ARM_INJECT_SERROR_ESR:
-		r = cpus_have_const_cap(ARM64_HAS_RAS_EXTN);
+		r = cpus_have_final_cap(ARM64_HAS_RAS_EXTN);
 		break;
 	case KVM_CAP_ARM_VM_IPA_SIZE:
 		r = get_kvm_ipa_limit();
@@ -1207,7 +1207,7 @@ static int kvm_vcpu_init_check_features(struct kvm_vcpu *vcpu,
 	if (!test_bit(KVM_ARM_VCPU_EL1_32BIT, &features))
 		return 0;
 
-	if (!cpus_have_const_cap(ARM64_HAS_32BIT_EL1))
+	if (!cpus_have_final_cap(ARM64_HAS_32BIT_EL1))
 		return -EINVAL;
 
 	/* MTE is incompatible with AArch32 */
@@ -1777,7 +1777,7 @@ static void hyp_install_host_vector(void)
 	 * Call initialization code, and switch to the full blown HYP code.
 	 * If the cpucaps haven't been finalized yet, something has gone very
 	 * wrong, and hyp will crash and burn when it uses any
-	 * cpus_have_const_cap() wrapper.
+	 * cpus_have_*_cap() wrapper.
 	 */
 	BUG_ON(!system_capabilities_finalized());
 	params = this_cpu_ptr_nvhe_sym(kvm_init_params);
@@ -2310,7 +2310,7 @@ static int __init init_hyp_mode(void)
 
 	if (is_protected_kvm_enabled()) {
 		if (IS_ENABLED(CONFIG_ARM64_PTR_AUTH_KERNEL) &&
-		    cpus_have_const_cap(ARM64_HAS_ADDRESS_AUTH))
+		    cpus_have_final_cap(ARM64_HAS_ADDRESS_AUTH))
 			pkvm_hyp_init_ptrauth();
 
 		init_cpu_logical_map();
diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c
index 95f6945c44325..a83c1d56a2940 100644
--- a/arch/arm64/kvm/guest.c
+++ b/arch/arm64/kvm/guest.c
@@ -815,7 +815,7 @@ int __kvm_arm_vcpu_get_events(struct kvm_vcpu *vcpu,
 			      struct kvm_vcpu_events *events)
 {
 	events->exception.serror_pending = !!(vcpu->arch.hcr_el2 & HCR_VSE);
-	events->exception.serror_has_esr = cpus_have_const_cap(ARM64_HAS_RAS_EXTN);
+	events->exception.serror_has_esr = cpus_have_final_cap(ARM64_HAS_RAS_EXTN);
 
 	if (events->exception.serror_pending && events->exception.serror_has_esr)
 		events->exception.serror_esr = vcpu_get_vsesr(vcpu);
@@ -837,7 +837,7 @@ int __kvm_arm_vcpu_set_events(struct kvm_vcpu *vcpu,
 	bool ext_dabt_pending = events->exception.ext_dabt_pending;
 
 	if (serror_pending && has_esr) {
-		if (!cpus_have_const_cap(ARM64_HAS_RAS_EXTN))
+		if (!cpus_have_final_cap(ARM64_HAS_RAS_EXTN))
 			return -EINVAL;
 
 		if (!((events->exception.serror_esr) & ~ESR_ELx_ISS_MASK))
diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
index f155b8c9e98c7..799d2c204bb8a 100644
--- a/arch/arm64/kvm/hyp/pgtable.c
+++ b/arch/arm64/kvm/hyp/pgtable.c
@@ -664,7 +664,7 @@ u64 kvm_get_vtcr(u64 mmfr0, u64 mmfr1, u32 phys_shift)
 
 static bool stage2_has_fwb(struct kvm_pgtable *pgt)
 {
-	if (!cpus_have_const_cap(ARM64_HAS_STAGE2_FWB))
+	if (!cpus_have_final_cap(ARM64_HAS_STAGE2_FWB))
 		return false;
 
 	return !(pgt->flags & KVM_PGTABLE_S2_NOFWB);
diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index 482280fe22d7c..e6061fd174b0b 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -1578,7 +1578,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 
 	if (device)
 		prot |= KVM_PGTABLE_PROT_DEVICE;
-	else if (cpus_have_const_cap(ARM64_HAS_CACHE_DIC))
+	else if (cpus_have_final_cap(ARM64_HAS_CACHE_DIC))
 		prot |= KVM_PGTABLE_PROT_X;
 
 	/*
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index e92ec810d4494..9318b6939b788 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -207,7 +207,7 @@ static bool access_dcsw(struct kvm_vcpu *vcpu,
 	 * CPU left in the system, and certainly not from non-secure
 	 * software).
 	 */
-	if (!cpus_have_const_cap(ARM64_HAS_STAGE2_FWB))
+	if (!cpus_have_final_cap(ARM64_HAS_STAGE2_FWB))
 		kvm_set_way_flush(vcpu);
 
 	return true;
diff --git a/arch/arm64/kvm/vgic/vgic-v3.c b/arch/arm64/kvm/vgic/vgic-v3.c
index 3dfc8b84e03e6..9465d3706ab9b 100644
--- a/arch/arm64/kvm/vgic/vgic-v3.c
+++ b/arch/arm64/kvm/vgic/vgic-v3.c
@@ -684,7 +684,7 @@ int vgic_v3_probe(const struct gic_kvm_info *info)
 	if (kvm_vgic_global_state.vcpu_base == 0)
 		kvm_info("disabling GICv2 emulation\n");
 
-	if (cpus_have_const_cap(ARM64_WORKAROUND_CAVIUM_30115)) {
+	if (cpus_have_final_cap(ARM64_WORKAROUND_CAVIUM_30115)) {
 		group0_trap = true;
 		group1_trap = true;
 	}
-- 
2.30.2


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