The following commit has been merged into the x86/core branch of tip: Commit-ID: 5b96185120bf588023760ac5bc9a0c96faf671e1 Gitweb: https://git.kernel.org/tip/5b96185120bf588023760ac5bc9a0c96faf671e1 Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx> AuthorDate: Tue, 08 Mar 2022 16:30:22 +01:00 Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx> CommitterDate: Tue, 08 Mar 2022 23:53:29 +01:00 x86/entry,xen: Early rewrite of restore_regs_and_return_to_kernel() 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@xxxxxxxxxx> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Acked-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx> Link: https://lore.kernel.org/r/20220308154317.815039833@xxxxxxxxxxxxx --- arch/x86/entry/entry_64.S | 11 ++++++++--- 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(+), 15 deletions(-) diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index 22e4e9a..f731393 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -609,7 +609,7 @@ SYM_INNER_LABEL(swapgs_restore_regs_and_return_to_usermode, SYM_L_GLOBAL) /* Restore RDI. */ popq %rdi swapgs - jmp native_iret + jmp .Lnative_iret SYM_INNER_LABEL(restore_regs_and_return_to_kernel, SYM_L_GLOBAL) @@ -626,9 +626,14 @@ SYM_INNER_LABEL(restore_regs_and_return_to_kernel, SYM_L_GLOBAL) * 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 /* * Are we returning to a stack segment from the LDT? Note: in diff --git a/arch/x86/include/asm/irqflags.h b/arch/x86/include/asm/irqflags.h index 8776139..111104d 100644 --- a/arch/x86/include/asm/irqflags.h +++ b/arch/x86/include/asm/irqflags.h @@ -141,13 +141,8 @@ 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;") #else #define SWAPGS swapgs -#define INTERRUPT_RETURN jmp native_iret #endif #endif #endif /* !__ASSEMBLY__ */ diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h index a69012e..7cd2874 100644 --- 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 *)) diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S index 9c63fc5..023761c 100644 --- a/arch/x86/kernel/head_64.S +++ b/arch/x86/kernel/head_64.S @@ -345,7 +345,6 @@ 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 @@ -426,6 +425,8 @@ 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. */ diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c index 06af2cf..6ecbbb0 100644 --- a/arch/x86/kernel/paravirt.c +++ b/arch/x86/kernel/paravirt.c @@ -132,8 +132,6 @@ void paravirt_set_sched_clock(u64 (*func)(void)) } /* These are in entry.S */ -extern void native_iret(void); - static struct resource reserve_ioports = { .start = 0, .end = IO_SPACE_LIMIT, @@ -397,8 +395,6 @@ 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); diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c index d47c3d1..3c7a55c 100644 --- 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_features(void) 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_start_kernel(void) 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_start_kernel(void) /* Install Xen paravirt ops */ pv_info = xen_info; pv_ops.cpu = xen_cpu_ops.cpu; - paravirt_iret = xen_iret; xen_init_irq_ops(); /* diff --git a/arch/x86/xen/xen-asm.S b/arch/x86/xen/xen-asm.S index e730e62..ee17b94 100644 --- a/arch/x86/xen/xen-asm.S +++ b/arch/x86/xen/xen-asm.S @@ -189,6 +189,7 @@ hypercall_iret = hypercall_page + __HYPERVISOR_iret * 32 */ SYM_CODE_START(xen_iret) UNWIND_HINT_EMPTY + ANNOTATE_NOENDBR pushq $0 jmp hypercall_iret SYM_CODE_END(xen_iret)
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