Messages in this thread Patch in this message | | | From | Lai Jiangshan <> | Date | Fri, 19 Nov 2021 15:51:44 +0800 | Subject | Re: [PATCH] x86/paravirt: Fix build PARAVIRT_XXL=y without XEN_PV |
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On Thu, Nov 18, 2021 at 7:14 AM Kirill A. Shutemov <kirill@shutemov.name> wrote: > > TDX is going to use CONFIG_PARAVIRT_XXL, but kernel fails to compile if > XEN_PV is not enabled: > > ld.lld: error: undefined symbol: xen_iret > > It happens because INTERRUPT_RETURN defined to use xen_iret if > CONFIG_PARAVIRT_XXL enabled regardless of CONFIG_XEN_PV. > > The issue is not visible in the current kernel because CONFIG_XEN_PV is > the only user of CONFIG_PARAVIRT_XXL and there's no way to enable them > separately. > > Rework code to define INTERRUPT_RETURN based on CONFIG_XEN_PV, not > CONFIG_PARAVIRT_XXL. > > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> > Cc: Juergen Gross <jgross@suse.com> > Cc: Deep Shah <sdeep@vmware.com> > Cc: "VMware, Inc." <pv-drivers@vmware.com> > --- > arch/x86/include/asm/irqflags.h | 7 +++++-- > arch/x86/include/asm/paravirt.h | 5 ----- > 2 files changed, 5 insertions(+), 7 deletions(-) > > diff --git a/arch/x86/include/asm/irqflags.h b/arch/x86/include/asm/irqflags.h > index b794b6da3214..3b8ddcb7be76 100644 > --- a/arch/x86/include/asm/irqflags.h > +++ b/arch/x86/include/asm/irqflags.h > @@ -118,8 +118,6 @@ static __always_inline unsigned long arch_local_irq_save(void) > #define SAVE_FLAGS pushfq; popq %rax > #endif > > -#define INTERRUPT_RETURN jmp native_iret > - > #endif > > #endif /* __ASSEMBLY__ */ > @@ -147,8 +145,13 @@ static __always_inline void arch_local_irq_restore(unsigned long flags) > #ifdef CONFIG_X86_64 > #ifdef CONFIG_XEN_PV > #define SWAPGS ALTERNATIVE "swapgs", "", X86_FEATURE_XENPV > +#define INTERRUPT_RETURN \ > + ANNOTATE_RETPOLINE_SAFE; \ > + ALTERNATIVE_TERNARY("jmp *paravirt_iret(%rip);", \ > + X86_FEATURE_XENPV, "jmp xen_iret;", "jmp native_iret;")
It is part of what CONFIG_PARAVIRT_XXL was designed for to enable pv-aware INTERRUPT_RETURN.
I would prefer xen_iret is defined as a weak symbol unconditionally. Like:
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index e38a4cf795d9..c0953f1b4559 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -635,6 +635,7 @@ SYM_INNER_LABEL_ALIGN(native_iret, SYM_L_GLOBAL) jnz native_irq_return_ldt #endif
+SYM_INNER_LABEL(xen_iret, SYM_L_WEAK) /* placeholder */ SYM_INNER_LABEL(native_irq_return_iret, SYM_L_GLOBAL) /* * This may fault. Non-paranoid faults on return to userspace are It will work when !CONFIG_XEN_PV
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