From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Roedel, Joerg" <Joerg.Roedel@amd.com>
Subject: Re: [PATCH v5] KVM: VMX: Execute WBINVD to keep data consistency
 with assigned devices
Date: Tue, 29 Jun 2010 12:14:04 +0200
Message-ID: <20100629101403.GB1788@amd.com>
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 <1277781419-13227-1-git-send-email-sheng@linux.intel.com>
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Cc: Avi Kivity <avi@redhat.com>, Marcelo Tosatti <mtosatti@redhat.com>,
	Jan Kiszka <jan.kiszka@siemens.com>,
	"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
	"Yaozu (Eddie) Dong" <eddie.dong@intel.com>
To: Sheng Yang <sheng@linux.intel.com>
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On Mon, Jun 28, 2010 at 11:16:59PM -0400, Sheng Yang wrote:
> Some guest device driver may leverage the "Non-Snoop" I/O, and explicitly
> WBINVD or CLFLUSH to a RAM space. Since migration may occur before WBINVD or
> CLFLUSH, we need to maintain data consistency either by:
> 1: flushing cache (wbinvd) when the guest is scheduled out if there is no
> wbinvd exit, or
> 2: execute wbinvd on all dirty physical CPUs when guest wbinvd exits.

Sorry for jumping in late. This code is not required on AMD platforms
because the io-page-tables for the AMD IOMMU have a FC bit (force
coherent) that must just be set. The current code does not set this bit
but I will prepare a patch for that. This wbinvd emulation code should
be avoided where possible.

	Joerg