search for: apply_pv_altern

...def CONFIG_PARAVIRT > > +/* > > + * Paravirt alternatives are applied much earlier than normal alternatives. > > + * They are only applied when running on a hypervisor. They replace some > > + * native instructions with calls to pv ops. > > + */ > > +void __init apply_pv_alternatives(void) > > +{ > > + setup_force_cpu_cap(X86_FEATURE_PV_OPS); > > Not for Xen HVM guests. >From what I can tell, HVM guests still use pv_time_ops and pv_mmu_ops.exit_mmap, right? > > + apply_alternatives(__pv_alt_instructions, __pv_alt_instructions_end); > >...

...def CONFIG_PARAVIRT > > +/* > > + * Paravirt alternatives are applied much earlier than normal alternatives. > > + * They are only applied when running on a hypervisor. They replace some > > + * native instructions with calls to pv ops. > > + */ > > +void __init apply_pv_alternatives(void) > > +{ > > + setup_force_cpu_cap(X86_FEATURE_PV_OPS); > > Not for Xen HVM guests. >From what I can tell, HVM guests still use pv_time_ops and pv_mmu_ops.exit_mmap, right? > > + apply_alternatives(__pv_alt_instructions, __pv_alt_instructions_end); > >...

...on a hypervisor, replace the native instructions with pv ops calls. The pv ops calls need to be available much earlier than when alternatives are normally applied. So put these alternatives in a dedicated ".pv_alternatives" section. So now these instructions may be patched twice: - in apply_pv_alternatives(), to allow the kernel to boot in the virtualized environment; - and again in apply_paravirt(), to enable performance improvements (e.g., replacing an indirect call with a direct call). That's a bit more complex, but overall this approach should cause less confusion than before beca...

...T >>> +/* >>> + * Paravirt alternatives are applied much earlier than normal alternatives. >>> + * They are only applied when running on a hypervisor. They replace some >>> + * native instructions with calls to pv ops. >>> + */ >>> +void __init apply_pv_alternatives(void) >>> +{ >>> + setup_force_cpu_cap(X86_FEATURE_PV_OPS); >> Not for Xen HVM guests. > From what I can tell, HVM guests still use pv_time_ops and > pv_mmu_ops.exit_mmap, right? Right, I forgot about that one. >>> + >>> void __init_or_modul...

> #ifdef CONFIG_PARAVIRT > +/* > + * Paravirt alternatives are applied much earlier than normal alternatives. > + * They are only applied when running on a hypervisor. They replace some > + * native instructions with calls to pv ops. > + */ > +void __init apply_pv_alternatives(void) > +{ > + setup_force_cpu_cap(X86_FEATURE_PV_OPS); Not for Xen HVM guests. > + apply_alternatives(__pv_alt_instructions, __pv_alt_instructions_end); > +} This is a problem (at least for Xen PV guests): apply_alternatives()->text_poke_early()->local_irq_save()->.....

...gt;>>> + * Paravirt alternatives are applied much earlier than normal alternatives. >>>> + * They are only applied when running on a hypervisor. They replace some >>>> + * native instructions with calls to pv ops. >>>> + */ >>>> +void __init apply_pv_alternatives(void) >>>> +{ >>>> + setup_force_cpu_cap(X86_FEATURE_PV_OPS); >>> Not for Xen HVM guests. >> From what I can tell, HVM guests still use pv_time_ops and >> pv_mmu_ops.exit_mmap, right? >> >>>> + apply_alternatives(__pv_alt_instruct...

...gt;>>> + * Paravirt alternatives are applied much earlier than normal alternatives. >>>> + * They are only applied when running on a hypervisor. They replace some >>>> + * native instructions with calls to pv ops. >>>> + */ >>>> +void __init apply_pv_alternatives(void) >>>> +{ >>>> + setup_force_cpu_cap(X86_FEATURE_PV_OPS); >>> Not for Xen HVM guests. >> From what I can tell, HVM guests still use pv_time_ops and >> pv_mmu_ops.exit_mmap, right? >> >>>> + apply_alternatives(__pv_alt_instruct...

...T >>> +/* >>> + * Paravirt alternatives are applied much earlier than normal alternatives. >>> + * They are only applied when running on a hypervisor. They replace some >>> + * native instructions with calls to pv ops. >>> + */ >>> +void __init apply_pv_alternatives(void) >>> +{ >>> + setup_force_cpu_cap(X86_FEATURE_PV_OPS); >> Not for Xen HVM guests. > From what I can tell, HVM guests still use pv_time_ops and > pv_mmu_ops.exit_mmap, right? > >>> + apply_alternatives(__pv_alt_instructions, __pv_alt_instructions_...

...+ * Paravirt alternatives are applied much earlier than normal alternatives. >>>>> + * They are only applied when running on a hypervisor. They replace some >>>>> + * native instructions with calls to pv ops. >>>>> + */ >>>>> +void __init apply_pv_alternatives(void) >>>>> +{ >>>>> + setup_force_cpu_cap(X86_FEATURE_PV_OPS); >>>> Not for Xen HVM guests. >>> From what I can tell, HVM guests still use pv_time_ops and >>> pv_mmu_ops.exit_mmap, right? >>> >>>>> + apply_al...

This changes the pv ops code generation to more closely match reality. For example, instead of: callq *0xffffffff81e3a400 (pv_irq_ops.save_fl) vmlinux will now show: pushfq pop %rax nop nop nop nop nop which is what the runtime version of the code will show in most cases. This idea was suggested by Andy Lutomirski. The benefits are: - For the most common runtime cases

This changes the pv ops code generation to more closely match reality. For example, instead of: callq *0xffffffff81e3a400 (pv_irq_ops.save_fl) vmlinux will now show: pushfq pop %rax nop nop nop nop nop which is what the runtime version of the code will show in most cases. This idea was suggested by Andy Lutomirski. The benefits are: - For the most common runtime cases