Messages in this thread Patch in this message | | | Date | Thu, 24 Feb 2022 15:52:05 +0100 | From | Peter Zijlstra <> | Subject | [PATCH v2 27/39] x86/entry,xen: Early rewrite of restore_regs_and_return_to_kernel() |
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By doing an early rewrite of 'jmp native_iret` in restore_regs_and_return_to_kernel() we can get rid of the last INTERRUPT_RETURN user and paravirt_iret.
Suggested-by: Andrew Cooper <Andrew.Cooper3@citrix.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> --- arch/x86/entry/entry_64.S | 12 ++++++++---- arch/x86/include/asm/irqflags.h | 5 ----- arch/x86/include/asm/paravirt_types.h | 1 - arch/x86/kernel/head_64.S | 3 ++- arch/x86/kernel/paravirt.c | 4 ---- arch/x86/xen/enlighten_pv.c | 7 ++++++- arch/x86/xen/xen-asm.S | 1 + 7 files changed, 17 insertions(+), 16 deletions(-)
--- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -620,7 +620,7 @@ SYM_INNER_LABEL(swapgs_restore_regs_and_ /* Restore RDI. */ popq %rdi swapgs - jmp native_iret + jmp .Lnative_iret SYM_INNER_LABEL(restore_regs_and_return_to_kernel, SYM_L_GLOBAL) @@ -637,11 +637,15 @@ SYM_INNER_LABEL(restore_regs_and_return_ * ARCH_HAS_MEMBARRIER_SYNC_CORE rely on IRET core serialization * when returning from IPI handler. */ - INTERRUPT_RETURN +#ifdef CONFIG_XEN_PV +SYM_INNER_LABEL(early_xen_iret_patch, SYM_L_GLOBAL) + ANNOTATE_NOENDBR + .byte 0xe9 + .long .Lnative_iret - (. + 4) +#endif -SYM_INNER_LABEL_ALIGN(native_iret, SYM_L_GLOBAL) +.Lnative_iret: UNWIND_HINT_IRET_REGS - ENDBR // paravirt_iret /* * Are we returning to a stack segment from the LDT? Note: in * 64-bit mode SS:RSP on the exception stack is always valid. --- a/arch/x86/include/asm/irqflags.h +++ b/arch/x86/include/asm/irqflags.h @@ -141,13 +141,8 @@ static __always_inline void arch_local_i #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;") #else #define SWAPGS swapgs -#define INTERRUPT_RETURN jmp native_iret #endif #endif #endif /* !__ASSEMBLY__ */ --- a/arch/x86/include/asm/paravirt_types.h +++ b/arch/x86/include/asm/paravirt_types.h @@ -272,7 +272,6 @@ struct paravirt_patch_template { extern struct pv_info pv_info; extern struct paravirt_patch_template pv_ops; -extern void (*paravirt_iret)(void); #define PARAVIRT_PATCH(x) \ (offsetof(struct paravirt_patch_template, x) / sizeof(void *)) --- a/arch/x86/kernel/head_64.S +++ b/arch/x86/kernel/head_64.S @@ -350,7 +350,6 @@ SYM_CODE_START_NOALIGN(vc_boot_ghcb) /* Remove Error Code */ addq $8, %rsp - /* Pure iret required here - don't use INTERRUPT_RETURN */ iretq SYM_CODE_END(vc_boot_ghcb) #endif @@ -434,6 +433,8 @@ SYM_CODE_END(early_idt_handler_common) * early_idt_handler_array can't be used because it returns via the * paravirtualized INTERRUPT_RETURN and pv-ops don't work that early. * + * XXX it does, fix this. + * * This handler will end up in the .init.text section and not be * available to boot secondary CPUs. */ --- a/arch/x86/kernel/paravirt.c +++ b/arch/x86/kernel/paravirt.c @@ -134,8 +134,6 @@ void paravirt_set_sched_clock(u64 (*func } /* These are in entry.S */ -extern void native_iret(void); - static struct resource reserve_ioports = { .start = 0, .end = IO_SPACE_LIMIT, @@ -399,8 +397,6 @@ struct paravirt_patch_template pv_ops = #ifdef CONFIG_PARAVIRT_XXL NOKPROBE_SYMBOL(native_load_idt); - -void (*paravirt_iret)(void) = native_iret; #endif EXPORT_SYMBOL(pv_ops); --- a/arch/x86/xen/enlighten_pv.c +++ b/arch/x86/xen/enlighten_pv.c @@ -1177,6 +1177,8 @@ static void __init xen_domu_set_legacy_f x86_platform.legacy.rtc = 0; } +extern void early_xen_iret_patch(void); + /* First C function to be called on Xen boot */ asmlinkage __visible void __init xen_start_kernel(void) { @@ -1187,6 +1189,10 @@ asmlinkage __visible void __init xen_sta if (!xen_start_info) return; + __text_gen_insn(&early_xen_iret_patch, + JMP32_INSN_OPCODE, &early_xen_iret_patch, &xen_iret, + JMP32_INSN_SIZE); + xen_domain_type = XEN_PV_DOMAIN; xen_start_flags = xen_start_info->flags; @@ -1195,7 +1201,6 @@ asmlinkage __visible void __init xen_sta /* Install Xen paravirt ops */ pv_info = xen_info; pv_ops.cpu = xen_cpu_ops.cpu; - paravirt_iret = xen_iret; xen_init_irq_ops(); /* --- a/arch/x86/xen/xen-asm.S +++ b/arch/x86/xen/xen-asm.S @@ -189,6 +189,7 @@ hypercall_iret = hypercall_page + __HYPE */ SYM_CODE_START(xen_iret) UNWIND_HINT_EMPTY + ANNOTATE_NOENDBR pushq $0 jmp hypercall_iret SYM_CODE_END(xen_iret)
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