Hi all, I''m trying ot figure out what that''s all about? I see in 64 PV domU, it''s being checked prior to returning from syscall. On the xen side, I see it tied to supervisor_mode_kernel, but the only info I find is changelog comment which suggests it''s purpose is to allow dom0 run in ring 0... So why the check in a domU kernel? Thanks, Mukesh | | | | <= Invisible ribbon campain against overuse of macros :). | | _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
On 20/11/08 22:42, "Mukesh Rathor" <mukesh.rathor@oracle.com> wrote:> I''m trying ot figure out what that''s all about? I see in 64 PV domU, it''s > being checked prior to returning from syscall. On the xen side, I see it tied > to supervisor_mode_kernel, but the only info I find is changelog comment which > suggests it''s purpose is to allow dom0 run in ring 0... So why the check in a > domU kernel?It''s useful if the hypervisor runs the guest kernel in ring 0. Current Xen doesn''t do that, but in future we may run 64-bit PV guests in HVM context as that may actually be faster. -- Keir _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Oh, cool. I was looking at syscalls on PV x86_64 guests, and one of my thoughts was running in HVM mode but do all MMU stuff using hypercalls like PV. Other than having to change the hyp domain create portions, setting things up, is there a technical reason it can''t be done today... thanks, Mukesh Keir Fraser wrote:> On 20/11/08 22:42, "Mukesh Rathor" <mukesh.rathor@oracle.com> wrote: > >> I''m trying ot figure out what that''s all about? I see in 64 PV domU, it''s >> being checked prior to returning from syscall. On the xen side, I see it tied >> to supervisor_mode_kernel, but the only info I find is changelog comment which >> suggests it''s purpose is to allow dom0 run in ring 0... So why the check in a >> domU kernel? > > It''s useful if the hypervisor runs the guest kernel in ring 0. Current Xen > doesn''t do that, but in future we may run 64-bit PV guests in HVM context as > that may actually be faster. > > -- Keir >_______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
No, not really. The hypervisor changes could likely not be that large. -- Keir On 20/11/08 23:03, "Mukesh Rathor" <mukesh.rathor@oracle.com> wrote:> Oh, cool. I was looking at syscalls on PV x86_64 guests, and one of my > thoughts was running in HVM mode but do all MMU stuff using hypercalls like > PV. Other than having to change the hyp domain create portions, setting things > up, is there a technical reason it can''t be done today... thanks, Mukesh > > Keir Fraser wrote: >> On 20/11/08 22:42, "Mukesh Rathor" <mukesh.rathor@oracle.com> wrote: >> >>> I''m trying ot figure out what that''s all about? I see in 64 PV domU, it''s >>> being checked prior to returning from syscall. On the xen side, I see it >>> tied >>> to supervisor_mode_kernel, but the only info I find is changelog comment >>> which >>> suggests it''s purpose is to allow dom0 run in ring 0... So why the check in >>> a >>> domU kernel? >> >> It''s useful if the hypervisor runs the guest kernel in ring 0. Current Xen >> doesn''t do that, but in future we may run 64-bit PV guests in HVM context as >> that may actually be faster. >> >> -- Keir >>_______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Jeremy Fitzhardinge
2008-Nov-24 01:11 UTC
Re: [Xen-devel] XENFEAT_supervisor_mode_kernel ???
Mukesh Rathor wrote:> Oh, cool. I was looking at syscalls on PV x86_64 guests, and one of my > thoughts was running in HVM mode but do all MMU stuff using hypercalls > like PV. Other than having to change the hyp domain create portions, > setting things up, is there a technical reason it can''t be done > today... thanks, MukeshIt''s sort of on my list of things to look at. But I''m still rather tied up in the dom0 work, so if you want to have a stab at it, go ahead! J _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Yup, I started looking into it, but significant progress after holidays/vacation late January. Thanks, mukesh Jeremy Fitzhardinge wrote:> Mukesh Rathor wrote: >> Oh, cool. I was looking at syscalls on PV x86_64 guests, and one of my >> thoughts was running in HVM mode but do all MMU stuff using hypercalls >> like PV. Other than having to change the hyp domain create portions, >> setting things up, is there a technical reason it can''t be done >> today... thanks, Mukesh > > It''s sort of on my list of things to look at. But I''m still rather tied > up in the dom0 work, so if you want to have a stab at it, go ahead! > > J_______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel