From mboxrd@z Thu Jan 1 00:00:00 1970 From: Boris Ostrovsky Subject: Re: [PATCH] x86/hvm: Provide list of emulated features in HVM CPUID leaf Date: Tue, 2 Feb 2016 18:30:22 -0500 Message-ID: <56B13C0E.5070905@oracle.com> References: <1454455041-4647-1-git-send-email-boris.ostrovsky@oracle.com> <56B13A2F.3070209@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <56B13A2F.3070209@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: Andrew Cooper , jbeulich@suse.com, keir@xen.org Cc: roger.pau@citrix.com, david.vrabel@citrix.com, xen-devel@lists.xen.org List-Id: xen-devel@lists.xenproject.org On 02/02/2016 06:22 PM, Andrew Cooper wrote: > On 02/02/2016 23:17, Boris Ostrovsky wrote: >> Hypervisor may choose which features to emulate for HVMlite guests. >> Guest will query the HVM CPUID leaf to find out what is available. >> >> Signed-off-by: Boris Ostrovsky > Roger also submitted a patch to do this. However, it is not > appropriate, so was dropped. > > An HVMLite domain should assume there are no emulated devices. The very > old legacy devices will never be implemented, and any others we care > about possibly implementing in the future have APCI-based ways of > indicating support. OK, so I wasn't the first one to come up with this ;-) I think for now I mostly care about APIC and for that I can use HW CPUID bit (which I believe is cleared for HVMlite guests). The trouble is that I need to present Linux as having APIC (boot code doesn't feel good if !cpu_has_apic) so I'll need to keep no-APIC emulation private to Xen-related code. Which is doable. -boris