linux-kernel - [RFC PATCH 65/67] KVM: x86: Mark the VM (TD) as bugged if non-coherent DMA is detected

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Date:   Mon, 16 Nov 2020 10:26:50 -0800
From:   isaku.yamahata@...el.com
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     isaku.yamahata@...el.com, isaku.yamahata@...il.com,
        Sean Christopherson <sean.j.christopherson@...el.com>
Subject: [RFC PATCH 65/67] KVM: x86: Mark the VM (TD) as bugged if non-coherent DMA is detected

From: Sean Christopherson <sean.j.christopherson@...el.com>

TDX is not supported on platforms with non-coherent IOMMUs, freak out if
one is encountered, and because SEPT doesn't allow the memtype control
that's needed to support non-coherent DMA.

Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
---
 arch/x86/kvm/x86.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 5566e7f25ce6..05dbdfdd7a8b 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -11144,6 +11144,7 @@ EXPORT_SYMBOL_GPL(kvm_arch_has_assigned_device);
 
 void kvm_arch_register_noncoherent_dma(struct kvm *kvm)
 {
+	KVM_BUG_ON(kvm->arch.vm_type == KVM_X86_TDX_VM, kvm);
 	atomic_inc(&kvm->arch.noncoherent_dma_count);
 }
 EXPORT_SYMBOL_GPL(kvm_arch_register_noncoherent_dma);
-- 
2.17.1