From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Chen, Tiejun" Subject: Re: [v4][PATCH 11/19] tools: introduce some new parameters to set rdm policy Date: Mon, 06 Jul 2015 21:34:27 +0800 Message-ID: <559A83E3.7040401@intel.com> References: <1435053450-25131-1-git-send-email-tiejun.chen@intel.com> <1435053450-25131-12-git-send-email-tiejun.chen@intel.com> <55933F7C.2050607@intel.com> <5593BBC8.1010402@eu.citrix.com> <5593C063.7000705@intel.com> <5593C7AC.8030901@eu.citrix.com> <5593CC19.9020200@intel.com> <5593EB53.5000601@eu.citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <5593EB53.5000601@eu.citrix.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: George Dunlap , Jan Beulich Cc: Ian Jackson , Stefano Stabellini , Wei Liu , Ian Campbell , "xen-devel@lists.xen.org" List-Id: xen-devel@lists.xenproject.org I think we should go back here. > I was involved in the design discussion, and from the very beginning I > probably saw your plan but misunderstood it. I wouldn't be surprised if > some others didn't quite understand what they were agreeing to. > > This way of doing things is different than the way we do it with most > other options relating to pci devices (e.g., pci_permissive, > pci_msitranslate, pci_sieze, &c). All of those options use a "default" > semantic: the domain-wide setting takes effect only if it's not set > locally. If the syntax looks the same but the semantics is different, > many people will be confused. If we're going to have the domain-wide > policy override the per-device policy, then the naming should make that > clear; for instance, "override=(strict|relaxed|none)", or > "strict_override=(1|0)". Jan, What about this? This is involving our policy so please take a look at this as well. George, Actually we don't mean the domain-wide policy always override the per-device policy, or the per-device policy always override the per-device policy. Here we just take "strict" as the highest priority when it conflicts in two cases. As I said previously myself may not answer this very correctly but now I can recall or understand that one reason is that different devices can share one RMRR entry, so its possible that these two or more per-device policies are not same. So we need this particular rule which is not same as before. So I still prefer to keep our original implementation. If I'm missing something or wrong, please Jan correct me. Thanks Tiejun > > I don't happen to think these "override" semantics are actually going to > turn out to be that useful; I do think a "default" semantic would be > useful. But I'd be content if the name of the current setting were > switched to "override" to make the semantics more clear. We can always > add in "default" at some later point if we really want. > > -George >