From mboxrd@z Thu Jan  1 00:00:00 1970
From: Keir Fraser <keir.xen@gmail.com>
Subject: Re: [help]: VPID tagged TLBs question.
Date: Thu, 26 Apr 2012 08:23:29 +0100
Message-ID: <CBBEB681.319A3%keir.xen@gmail.com>
References: <20120425180729.6a8f7127@mantra.us.oracle.com>
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To: Mukesh Rathor <mukesh.rathor@oracle.com>, "Xen-devel@lists.xensource.com" <Xen-devel@lists.xensource.com>, Ian Campbell <Ian.Campbell@citrix.com>
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On 26/04/2012 02:07, "Mukesh Rathor" <mukesh.rathor@oracle.com> wrote:

> However, I don't understand the use of hvm_asid_flush_core which
> it appears will cause all HVM vcpu's to get new vpid/asid, hence, discard
> all previously used VPID tagged TLBs. In particular, consider a PV
> guest:
> 
> write_ptbase -> write_cr3 -> hvm_flush_guest_tlbs -> hvm_asid_flush_core().
> 
> Since the PV guest is only using VPID 0 tagged TLBs, why do we need to
> flush all TLBs for all HVM guests?

It's just being conservative, as callers of write_cr3 may assume that the
TLB is entirely flushed, for all guests.

 -- Keir