Messages in this thread | | | Date | Fri, 19 Nov 2021 13:20:48 +0300 | From | "Kirill A. Shutemov" <> | Subject | Re: [PATCH] x86/paravirt: Fix build PARAVIRT_XXL=y without XEN_PV |
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On Fri, Nov 19, 2021 at 03:51:44PM +0800, Lai Jiangshan wrote: > 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.
That's very vague statement.
Could you elaborate on what is wrong with proposed fix?
> 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
It pollutes namespace for no particular reason. I don't see it justified.
-- Kirill A. Shutemov
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