linux-kernel - Re: [kvm-devel] [PATCH 1/8] KVM: PVDMA Host: Handle reqeusts for guest DMA mappings

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Message-ID: <20071112155522.GF6466@amd.com>
Date:	Mon, 12 Nov 2007 16:55:22 +0100
From:	"Joerg Roedel" <joerg.roedel@....com>
To:	"Amit Shah" <amit.shah@...ranet.com>
cc:	kvm-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org
Subject: Re: [kvm-devel] [PATCH 1/8] KVM: PVDMA Host: Handle reqeusts
 for guest DMA mappings

On Wed, Nov 07, 2007 at 04:21:02PM +0200, Amit Shah wrote:
> @@ -1649,6 +1913,15 @@ int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
>  	}
>  
>  	switch (nr) {
> +	case KVM_PV_DMA_MAP:
> +		ret = pv_map_hypercall(vcpu, a0, a1);
> +		break;
> +	case KVM_PV_DMA_UNMAP:
> +		ret = pv_unmap_hypercall(vcpu, a0);
> +		break;
> +	case KVM_PV_PCI_DEVICE:
> +		ret = pv_mapped_pci_device_hypercall(vcpu, a0);
> +		break;
>  	default:
>  		ret = -KVM_ENOSYS;
>  		break;

How does synchronization work with that design? I don't see a hypercall
to synchronize de DMA buffers. It will only work if GART is used as the
dma_ops backend on the host side and not with SWIOTLB. But GART can be
configured away.  Or do I miss something?

Joerg

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