linux-kernel - [PATCH 3/4] KVM: x86: hyper-v: Fix the maximum number of sparse banks for XMM fast TLB flush hypercalls

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Date:   Tue, 22 Feb 2022 16:46:41 +0100
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Siddharth Chandrasekaran <sidcha@...zon.de>,
        linux-kernel@...r.kernel.org
Subject: [PATCH 3/4] KVM: x86: hyper-v: Fix the maximum number of sparse banks for XMM fast TLB flush hypercalls

When TLB flush hypercalls (HVCALL_FLUSH_VIRTUAL_ADDRESS_{LIST,SPACE}_EX are
issued in 'XMM fast' mode, the maximum number of allowed sparse_banks is
not 'HV_HYPERCALL_MAX_XMM_REGISTERS - 1' (5) but twice as many (10) as each
XMM register is 128 bit long and can hold two 64 bit long banks.

Fixes: 5974565bc26d ("KVM: x86: kvm_hv_flush_tlb use inputs from XMM registers")
Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
---
 arch/x86/kvm/hyperv.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 714af3b94f31..6dda93bf98ae 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1820,7 +1820,8 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc)
 
 		if (!all_cpus) {
 			if (hc->fast) {
-				if (sparse_banks_len > HV_HYPERCALL_MAX_XMM_REGISTERS - 1)
+				/* XMM0 is already consumed, each XMM holds two sparse banks. */
+				if (sparse_banks_len > 2 * (HV_HYPERCALL_MAX_XMM_REGISTERS - 1))
 					return HV_STATUS_INVALID_HYPERCALL_INPUT;
 				for (i = 0; i < sparse_banks_len; i += 2) {
 					sparse_banks[i] = sse128_lo(hc->xmm[i / 2 + 1]);
-- 
2.35.1