I''m working on passing vtsc=[0|1] (rdtsc emulation) from the vm.cfg file into xen. I was using the superpages vm.cfg implementation as a guide, but I see the domain builder interface for superpages changed in c/s 19963 to pass the value via a flag in a pad byte in struct xc_dom_image. Was this change due to some backward compatibility reason? This looks like a nicer interface, but is there another pad byte I can/should use? If not, what''s the best way then to pass the vtsc value from the tools to Xen? Also, will I be able to use the same interface for both HVM and PV, or should I use the HVM param interface for HVM domains (using the HPET parameter as a model)? Thanks, Dan _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
> Was this change due to some backward compatibility reason?I found the compatibility issue describe here: http://xen.markmail.org/message/usjxnjyp3csm3uct?q=superpages+date:200907 So it seems even more important that I somehow claim a field (or at least a bit) in struct xc_dom_image. Any help to get this right would be appreciated as getting it wrong clearly has some non-obvious consequences. Thanks, Dan> -----Original Message----- > From: Dan Magenheimer > Sent: Tuesday, September 15, 2009 3:58 PM > To: Xen-Devel (E-mail) > Subject: vtsc in domain builder > > > I''m working on passing vtsc=[0|1] (rdtsc emulation) from > the vm.cfg file into xen. > > I was using the superpages vm.cfg implementation as a guide, > but I see the domain builder interface for superpages changed > in c/s 19963 to pass the value via a flag in a pad byte in > struct xc_dom_image. Was this change due to some backward > compatibility reason? This looks like a nicer interface, > but is there another pad byte I can/should use? If not, > what''s the best way then to pass the vtsc value from the > tools to Xen? > > Also, will I be able to use the same interface for both > HVM and PV, or should I use the HVM param interface for > HVM domains (using the HPET parameter as a model)? > > Thanks, > Dan >_______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
On 16/09/2009 00:32, "Dan Magenheimer" <dan.magenheimer@oracle.com> wrote:>> Was this change due to some backward compatibility reason? > > I found the compatibility issue describe here: > > http://xen.markmail.org/message/usjxnjyp3csm3uct?q=superpages+date:200907 > > So it seems even more important that I somehow claim > a field (or at least a bit) in struct xc_dom_image. > Any help to get this right would be appreciated > as getting it wrong clearly has some non-obvious > consequences.Well, the main issue was the original patch broke API compatibility. Fixing ABI compatibility in the fixup patch was just gravy. I suggest you split the superpages int8_t into a bitfield, e.g: uint8_t superpages:1, vtsc:1; Putting superpages first should maintain compatibility as far as possible. The bitfield has to be switched to be unsigned - we got bit by that before. -- Keir _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel