Stupid Xen vs KVM question
This code in arch/x86/kernel/entry_32.S is wrong: #ifdef CONFIG_PARAVIRT /* * The kernel can't run on a non-flat stack if paravirt mode * is active. Rather than try to fixup the high bits of * ESP, bypass this code entirely. This may break DOSemu * and/or Wine support in a paravirt VM, although the option * is still available to implement the setting of the high * 16-bits in the INTERRUPT_RETURN paravirt-op. */ cmpl $0, pv_info+PARAVIRT_enabled jne restore_nocheck #endif On KVM guests, it notices that paravirt is enabled and bails. It should work fine on KVM -- the condition it should be checking is whether we have native segmentation. Do you know the right way to ask that? Thanks, Andy -- Andy Lutomirski AMA Capital Management, LLC -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: Stupid Xen vs KVM question
On Thu, Dec 04, 2014 at 02:59:48PM -0800, Andy Lutomirski wrote: > This code in arch/x86/kernel/entry_32.S is wrong: > > #ifdef CONFIG_PARAVIRT > /* > * The kernel can't run on a non-flat stack if paravirt mode > * is active. Rather than try to fixup the high bits of > * ESP, bypass this code entirely. This may break DOSemu > * and/or Wine support in a paravirt VM, although the option > * is still available to implement the setting of the high > * 16-bits in the INTERRUPT_RETURN paravirt-op. > */ > cmpl $0, pv_info+PARAVIRT_enabled > jne restore_nocheck > #endif > > On KVM guests, it notices that paravirt is enabled and bails. It > should work fine on KVM -- the condition it should be checking is > whether we have native segmentation. > > Do you know the right way to ask that? We could do a simple thing - which is that the paravirt_enabled could have the value 1 for Xen and 2 for KVM. The assembler logic would be inverted and just check for 1. I am not going to attempt to write the assembler code :-) > > Thanks, > Andy > > -- > Andy Lutomirski > AMA Capital Management, LLC -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: Stupid Xen vs KVM question
On 05/12/2014 03:24, Konrad Rzeszutek Wilk wrote: > We could do a simple thing - which is that the paravirt_enabled > could have the value 1 for Xen and 2 for KVM. The assembler logic > would be inverted and just check for 1. I am not going to attempt > to write the assembler code :-) Wouldn't Xen HVM also want to be 2? Paolo -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: Stupid Xen vs KVM question
On Fri, Dec 05, 2014 at 08:29:54AM +0100, Paolo Bonzini wrote: > > > On 05/12/2014 03:24, Konrad Rzeszutek Wilk wrote: > > We could do a simple thing - which is that the paravirt_enabled > > could have the value 1 for Xen and 2 for KVM. The assembler logic > > would be inverted and just check for 1. I am not going to attempt > > to write the assembler code :-) > > Wouldn't Xen HVM also want to be 2? Oddly enough it was never set! Looking at where the paravit_enabled() macro is used, on KVM it could be just set to zero. > > Paolo -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: Stupid Xen vs KVM question
On Dec 5, 2014 8:09 AM, "Konrad Rzeszutek Wilk" wrote: > > On Fri, Dec 05, 2014 at 08:29:54AM +0100, Paolo Bonzini wrote: > > > > > > On 05/12/2014 03:24, Konrad Rzeszutek Wilk wrote: > > > We could do a simple thing - which is that the paravirt_enabled > > > could have the value 1 for Xen and 2 for KVM. The assembler logic > > > would be inverted and just check for 1. I am not going to attempt > > > to write the assembler code :-) > > > > Wouldn't Xen HVM also want to be 2? > > Oddly enough it was never set! > > Looking at where the paravit_enabled() macro is used, on KVM it could > be just set to zero. I noticed that KVM is setting paravirt_enabled = 1 twice, once the main kvm guest code and once in kvmclock. Will the EBDA code in head.c care? That would also increase sanity a little IMO. We currently have "paravirt" meaning that the normal HW architecture isn't present (Den, lguest) and "paravirt" meaning that there are extra optional-to-use hypervisor features (KVM, etc). --Andy -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
