Re: [PATCH v5] KVM: VMX: Execute WBINVD to keep data consistency with assigned devices

Roedel, Joerg
2010-06-29T10:35:23Z

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