linux-kernel - [PATCH V2 4/5] KVM: arm64: Drop check_kvm_target

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Message-Id: <1628744994-16623-5-git-send-email-anshuman.khandual@arm.com>
Date:   Thu, 12 Aug 2021 10:39:53 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     Anshuman Khandual <anshuman.khandual@....com>,
        Marc Zyngier <maz@...nel.org>,
        James Morse <james.morse@....com>,
        Alexandru Elisei <alexandru.elisei@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, kvmarm@...ts.cs.columbia.edu,
        linux-kernel@...r.kernel.org
Subject: [PATCH V2 4/5] KVM: arm64: Drop check_kvm_target_cpu() based percpu probe

kvm_target_cpu() never returns a negative error code, so check_kvm_target()
would never have 'ret' filled with a negative error code. Hence the percpu
probe via check_kvm_target_cpu() does not make sense as its never going to
find an unsupported CPU, forcing kvm_arch_init() to exit early. Hence lets
just drop this percpu probe (and also check_kvm_target_cpu()) altogether.

While here, this also changes kvm_target_cpu() return type to a u32, making
it explicit that an error code will not be returned from this function.

Cc: Marc Zyngier <maz@...nel.org>
Cc: James Morse <james.morse@....com>
Cc: Alexandru Elisei <alexandru.elisei@....com>
Cc: Suzuki K Poulose <suzuki.poulose@....com>
Cc: Catalin Marinas <catalin.marinas@....com>
Cc: Will Deacon <will@...nel.org>
Cc: linux-arm-kernel@...ts.infradead.org
Cc: kvmarm@...ts.cs.columbia.edu
Cc: linux-kernel@...r.kernel.org
Acked-by: Will Deacon <will@...nel.org>
Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
---
 arch/arm64/include/asm/kvm_host.h |  2 +-
 arch/arm64/kvm/arm.c              | 16 +---------------
 arch/arm64/kvm/guest.c            |  4 ++--
 3 files changed, 4 insertions(+), 18 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 41911585ae0c..26bbd84a02de 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -66,7 +66,7 @@ DECLARE_STATIC_KEY_FALSE(userspace_irqchip_in_use);
 extern unsigned int kvm_sve_max_vl;
 int kvm_arm_init_sve(void);
 
-int __attribute_const__ kvm_target_cpu(void);
+u32 __attribute_const__ kvm_target_cpu(void);
 int kvm_reset_vcpu(struct kvm_vcpu *vcpu);
 void kvm_arm_vcpu_destroy(struct kvm_vcpu *vcpu);
 
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 19560e457c11..ee9b1166f330 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -1035,7 +1035,7 @@ static int kvm_vcpu_set_target(struct kvm_vcpu *vcpu,
 			       const struct kvm_vcpu_init *init)
 {
 	unsigned int i, ret;
-	int phys_target = kvm_target_cpu();
+	u32 phys_target = kvm_target_cpu();
 
 	if (init->target != phys_target)
 		return -EINVAL;
@@ -2010,11 +2010,6 @@ static int finalize_hyp_mode(void)
 	return 0;
 }
 
-static void check_kvm_target_cpu(void *ret)
-{
-	*(int *)ret = kvm_target_cpu();
-}
-
 struct kvm_vcpu *kvm_mpidr_to_vcpu(struct kvm *kvm, unsigned long mpidr)
 {
 	struct kvm_vcpu *vcpu;
@@ -2074,7 +2069,6 @@ void kvm_arch_irq_bypass_start(struct irq_bypass_consumer *cons)
 int kvm_arch_init(void *opaque)
 {
 	int err;
-	int ret, cpu;
 	bool in_hyp_mode;
 
 	if (!is_hyp_mode_available()) {
@@ -2089,14 +2083,6 @@ int kvm_arch_init(void *opaque)
 		kvm_info("Guests without required CPU erratum workarounds can deadlock system!\n" \
 			 "Only trusted guests should be used on this system.\n");
 
-	for_each_online_cpu(cpu) {
-		smp_call_function_single(cpu, check_kvm_target_cpu, &ret, 1);
-		if (ret < 0) {
-			kvm_err("Error, CPU %d not supported!\n", cpu);
-			return -ENODEV;
-		}
-	}
-
 	err = kvm_set_ipa_limit();
 	if (err)
 		return err;
diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c
index 1dfb83578277..8ce850fa7b49 100644
--- a/arch/arm64/kvm/guest.c
+++ b/arch/arm64/kvm/guest.c
@@ -842,7 +842,7 @@ int __kvm_arm_vcpu_set_events(struct kvm_vcpu *vcpu,
 	return 0;
 }
 
-int __attribute_const__ kvm_target_cpu(void)
+u32 __attribute_const__ kvm_target_cpu(void)
 {
 	unsigned long implementor = read_cpuid_implementor();
 	unsigned long part_number = read_cpuid_part_number();
@@ -874,7 +874,7 @@ int __attribute_const__ kvm_target_cpu(void)
 
 int kvm_vcpu_preferred_target(struct kvm_vcpu_init *init)
 {
-	int target = kvm_target_cpu();
+	u32 target = kvm_target_cpu();
 
 	if (target < 0)
 		return -ENODEV;
-- 
2.20.1