linux-kernel - [PATCH v9 09/40] KVM: x86: hyper-v: Use HV_MAX_SPARSE_VCPU_BANKS/HV_VCPUS_PER_SPARSE

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Message-Id: <20220803134110.397885-10-vkuznets@redhat.com>
Date:   Wed,  3 Aug 2022 15:40:39 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>
Cc:     Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Michael Kelley <mikelley@...rosoft.com>,
        Siddharth Chandrasekaran <sidcha@...zon.de>,
        Yuan Yao <yuan.yao@...ux.intel.com>,
        Maxim Levitsky <mlevitsk@...hat.com>,
        linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v9 09/40] KVM: x86: hyper-v: Use HV_MAX_SPARSE_VCPU_BANKS/HV_VCPUS_PER_SPARSE_BANK instead of raw '64'

It may not be clear from where the '64' limit for the maximum sparse
bank number comes from, use HV_MAX_SPARSE_VCPU_BANKS define instead.
Use HV_VCPUS_PER_SPARSE_BANK in KVM_HV_MAX_SPARSE_VCPU_SET_BITS's
definition. Opportunistically adjust the comment around BUILD_BUG_ON().

No functional change.

Reviewed-by: Maxim Levitsky <mlevitsk@...hat.com>
Suggested-by: Sean Christopherson <seanjc@...gle.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
---
 arch/x86/kvm/hyperv.c | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index f32b92d295fe..19899cce2927 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -43,7 +43,7 @@
 /* "Hv#1" signature */
 #define HYPERV_CPUID_SIGNATURE_EAX 0x31237648
 
-#define KVM_HV_MAX_SPARSE_VCPU_SET_BITS DIV_ROUND_UP(KVM_MAX_VCPUS, 64)
+#define KVM_HV_MAX_SPARSE_VCPU_SET_BITS DIV_ROUND_UP(KVM_MAX_VCPUS, HV_VCPUS_PER_SPARSE_BANK)
 
 static void stimer_mark_pending(struct kvm_vcpu_hv_stimer *stimer,
 				bool vcpu_kick);
@@ -1799,7 +1799,7 @@ static u64 kvm_get_sparse_vp_set(struct kvm *kvm, struct kvm_hv_hcall *hc,
 				 u64 *sparse_banks, int consumed_xmm_halves,
 				 gpa_t offset)
 {
-	if (hc->var_cnt > 64)
+	if (hc->var_cnt > HV_MAX_SPARSE_VCPU_BANKS)
 		return -EINVAL;
 
 	/* Cap var_cnt to ignore banks that cannot contain a legal VP index. */
@@ -1909,12 +1909,11 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc)
 	gpa_t data_offset;
 
 	/*
-	 * The Hyper-V TLFS doesn't allow more than 64 sparse banks, e.g. the
-	 * valid mask is a u64.  Fail the build if KVM's max allowed number of
-	 * vCPUs (>4096) would exceed this limit, KVM will additional changes
-	 * for Hyper-V support to avoid setting the guest up to fail.
+	 * The Hyper-V TLFS doesn't allow more than HV_MAX_SPARSE_VCPU_BANKS
+	 * sparse banks. Fail the build if KVM's max allowed number of
+	 * vCPUs (>4096) exceeds this limit.
 	 */
-	BUILD_BUG_ON(KVM_HV_MAX_SPARSE_VCPU_SET_BITS > 64);
+	BUILD_BUG_ON(KVM_HV_MAX_SPARSE_VCPU_SET_BITS > HV_MAX_SPARSE_VCPU_BANKS);
 
 	if (!hc->fast && is_guest_mode(vcpu)) {
 		hc->ingpa = translate_nested_gpa(vcpu, hc->ingpa, 0, NULL);
-- 
2.35.3