search for: crosshvpara

On Thu, Sep 18, 2014 at 2:57 PM, H. Peter Anvin <hpa at zytor.com> wrote: > On 09/18/2014 02:46 PM, David Hepkin wrote: >> I'm not sure what you mean by "this mechanism?" Are you suggesting that each hypervisor put "CrossHVPara\0" somewhere in the 0x40000000 - 0x400fffff CPUID range, and an OS has to do a full scan of this CPUID range on boot to find it? That seems pretty inefficient. An OS will take 1000's of hypervisor intercepts on every boot just to search this CPUID range. >> >> I suggest we co...

On Thu, Sep 18, 2014 at 2:57 PM, H. Peter Anvin <hpa at zytor.com> wrote: > On 09/18/2014 02:46 PM, David Hepkin wrote: >> I'm not sure what you mean by "this mechanism?" Are you suggesting that each hypervisor put "CrossHVPara\0" somewhere in the 0x40000000 - 0x400fffff CPUID range, and an OS has to do a full scan of this CPUID range on boot to find it? That seems pretty inefficient. An OS will take 1000's of hypervisor intercepts on every boot just to search this CPUID range. >> >> I suggest we co...

...UID leaves 0x400xyz00 for >> "KVMKVMKVM\0\0\0", so at least Linux can handle the KVM leaves being >> in a somewhat variable location. >> >> Do we consider this mechanism to work across all hypervisors and >> guests? That is, could we put something like "CrossHVPara\0" >> somewhere in that range, where each hypervisor would be free to decide >> exactly where it ends up? > > That's also possible, but extending the hypervisor CPUID range > beywond 400000FFH is not officially sanctioned by Intel. > > Xen started doing that in o...

...UID leaves 0x400xyz00 for >> "KVMKVMKVM\0\0\0", so at least Linux can handle the KVM leaves being >> in a somewhat variable location. >> >> Do we consider this mechanism to work across all hypervisors and >> guests? That is, could we put something like "CrossHVPara\0" >> somewhere in that range, where each hypervisor would be free to decide >> exactly where it ends up? > > That's also possible, but extending the hypervisor CPUID range > beywond 400000FFH is not officially sanctioned by Intel. > > Xen started doing that in o...

I'm not sure what you mean by "this mechanism?" Are you suggesting that each hypervisor put "CrossHVPara\0" somewhere in the 0x40000000 - 0x400fffff CPUID range, and an OS has to do a full scan of this CPUID range on boot to find it? That seems pretty inefficient. An OS will take 1000's of hypervisor intercepts on every boot just to search this CPUID range. I suggest we come to consensus o...

I'm not sure what you mean by "this mechanism?" Are you suggesting that each hypervisor put "CrossHVPara\0" somewhere in the 0x40000000 - 0x400fffff CPUID range, and an OS has to do a full scan of this CPUID range on boot to find it? That seems pretty inefficient. An OS will take 1000's of hypervisor intercepts on every boot just to search this CPUID range. I suggest we come to consensus o...

...tries to detect a hypervisor by searching CPUID leaves 0x400xyz00 for "KVMKVMKVM\0\0\0", so at least Linux can handle the KVM leaves being in a somewhat variable location. Do we consider this mechanism to work across all hypervisors and guests? That is, could we put something like "CrossHVPara\0" somewhere in that range, where each hypervisor would be free to decide exactly where it ends up? --Andy

...tries to detect a hypervisor by searching CPUID leaves 0x400xyz00 for "KVMKVMKVM\0\0\0", so at least Linux can handle the KVM leaves being in a somewhat variable location. Do we consider this mechanism to work across all hypervisors and guests? That is, could we put something like "CrossHVPara\0" somewhere in that range, where each hypervisor would be free to decide exactly where it ends up? --Andy

...com> wrote: > On Thu, Sep 18, 2014 at 3:07 PM, Andy Lutomirski <luto at amacapital.net> wrote: > >> So, as a concrete straw-man: >> >> CPUID leaf 0x48000000 would return a maximum leaf number in EAX (e.g. >> 0x48000001) along with a signature value (e.g. "CrossHVPara\0") in >> EBX, ECX, and EDX. >> >> CPUID 0x48000001.EAX would contain an MSR number to read to get a >> random number if supported and zero if not supported. >> >> Questions: >> >> 1. Can we use a fixed MSR number? This would be a little bit sim...

...com> wrote: > On Thu, Sep 18, 2014 at 3:07 PM, Andy Lutomirski <luto at amacapital.net> wrote: > >> So, as a concrete straw-man: >> >> CPUID leaf 0x48000000 would return a maximum leaf number in EAX (e.g. >> 0x48000001) along with a signature value (e.g. "CrossHVPara\0") in >> EBX, ECX, and EDX. >> >> CPUID 0x48000001.EAX would contain an MSR number to read to get a >> random number if supported and zero if not supported. >> >> Questions: >> >> 1. Can we use a fixed MSR number? This would be a little bit sim...

...sor by searching CPUID leaves 0x400xyz00 for > "KVMKVMKVM\0\0\0", so at least Linux can handle the KVM leaves being > in a somewhat variable location. > > Do we consider this mechanism to work across all hypervisors and > guests? That is, could we put something like "CrossHVPara\0" > somewhere in that range, where each hypervisor would be free to decide > exactly where it ends up? That's also possible, but extending the hypervisor CPUID range beywond 400000FFH is not officially sanctioned by Intel. Xen started doing that in order to expose both Hyper-V and...

On 09/18/2014 02:46 PM, David Hepkin wrote: > I'm not sure what you mean by "this mechanism?" Are you suggesting that each hypervisor put "CrossHVPara\0" somewhere in the 0x40000000 - 0x400fffff CPUID range, and an OS has to do a full scan of this CPUID range on boot to find it? That seems pretty inefficient. An OS will take 1000's of hypervisor intercepts on every boot just to search this CPUID range. > > I suggest we come to c...

On Thu, Sep 18, 2014 at 2:46 PM, David Hepkin <davidhep at microsoft.com> wrote: > I'm not sure what you mean by "this mechanism?" Are you suggesting that each hypervisor put "CrossHVPara\0" somewhere in the 0x40000000 - 0x400fffff CPUID range, and an OS has to do a full scan of this CPUID range on boot to find it? That seems pretty inefficient. An OS will take 1000's of hypervisor intercepts on every boot just to search this CPUID range. Linux already does this, which i...

On Thu, Sep 18, 2014 at 3:07 PM, Andy Lutomirski <luto at amacapital.net> wrote: > So, as a concrete straw-man: > > CPUID leaf 0x48000000 would return a maximum leaf number in EAX (e.g. > 0x48000001) along with a signature value (e.g. "CrossHVPara\0") in > EBX, ECX, and EDX. > > CPUID 0x48000001.EAX would contain an MSR number to read to get a > random number if supported and zero if not supported. > > Questions: > > 1. Can we use a fixed MSR number? This would be a little bit simpler, > but it would depend o...

...On Thu, Sep 18, 2014 at 3:07 PM, Andy Lutomirski <luto at amacapital.net> wrote: >> >>> So, as a concrete straw-man: >>> >>> CPUID leaf 0x48000000 would return a maximum leaf number in EAX (e.g. >>> 0x48000001) along with a signature value (e.g. "CrossHVPara\0") in >>> EBX, ECX, and EDX. >>> >>> CPUID 0x48000001.EAX would contain an MSR number to read to get a >>> random number if supported and zero if not supported. >>> >>> Questions: >>> >>> 1. Can we use a fixed MSR number?...

...pervisor by searching CPUID leaves 0x400xyz00 for >"KVMKVMKVM\0\0\0", so at least Linux can handle the KVM leaves being >in a somewhat variable location. > >Do we consider this mechanism to work across all hypervisors and >guests? That is, could we put something like "CrossHVPara\0" >somewhere in that range, where each hypervisor would be free to decide >exactly where it ends up? > >--Andy -- Sent from my mobile phone. Please pardon brevity and lack of formatting.

> -----Original Message----- > From: Paolo Bonzini [mailto:paolo.bonzini at gmail.com] On Behalf Of Paolo > Bonzini > Sent: Thursday, September 18, 2014 10:18 AM > To: Nakajima, Jun; KY Srinivasan > Cc: Mathew John; Theodore Ts'o; John Starks; kvm list; Gleb Natapov; Niels > Ferguson; Andy Lutomirski; David Hepkin; H. Peter Anvin; Jake Oshins; Linux > Virtualization

> -----Original Message----- > From: Paolo Bonzini [mailto:paolo.bonzini at gmail.com] On Behalf Of Paolo > Bonzini > Sent: Thursday, September 18, 2014 10:18 AM > To: Nakajima, Jun; KY Srinivasan > Cc: Mathew John; Theodore Ts'o; John Starks; kvm list; Gleb Natapov; Niels > Ferguson; Andy Lutomirski; David Hepkin; H. Peter Anvin; Jake Oshins; Linux > Virtualization

...at 3:07 PM, Andy Lutomirski <luto at amacapital.net> wrote: >>> >>>> So, as a concrete straw-man: >>>> >>>> CPUID leaf 0x48000000 would return a maximum leaf number in EAX (e.g. >>>> 0x48000001) along with a signature value (e.g. "CrossHVPara\0") in >>>> EBX, ECX, and EDX. >>>> >>>> CPUID 0x48000001.EAX would contain an MSR number to read to get a >>>> random number if supported and zero if not supported. >>>> >>>> Questions: >>>> >>>> 1...

...at 3:07 PM, Andy Lutomirski <luto at amacapital.net> wrote: >>> >>>> So, as a concrete straw-man: >>>> >>>> CPUID leaf 0x48000000 would return a maximum leaf number in EAX (e.g. >>>> 0x48000001) along with a signature value (e.g. "CrossHVPara\0") in >>>> EBX, ECX, and EDX. >>>> >>>> CPUID 0x48000001.EAX would contain an MSR number to read to get a >>>> random number if supported and zero if not supported. >>>> >>>> Questions: >>>> >>>> 1...