Re: [PATCH] x86, paravirt, xen: Remove the 64-bit irq_enable_sysexit pvop

[Andy Lutomirski]

On Fri, Apr 3, 2015 at 3:51 PM, Andy Lutomirski <luto@xxxxxxxxxx> wrote:
> We don't use irq_enable_sysexit on 64-bit kernels any more.  Remove
> all the paravirt and Xen machinery to support it on 64-bit kernels.
>
> Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx>

Hi, Ingo,

Can you pick this up in -tip?  It cleans up code that would otherwise
be unreachable in 4.1, but it doesn't fix any bugs, so waiting for 4.2
would be fine as well.

--Andy

> ---
>
> I haven't actually tested this on Xen, but it builds for me.
>
>  arch/x86/ia32/ia32entry.S             |  6 ------
>  arch/x86/include/asm/paravirt_types.h |  7 ++++---
>  arch/x86/kernel/asm-offsets.c         |  2 ++
>  arch/x86/kernel/paravirt.c            |  4 +++-
>  arch/x86/kernel/paravirt_patch_64.c   |  1 -
>  arch/x86/xen/enlighten.c              |  3 ++-
>  arch/x86/xen/xen-asm_64.S             | 16 ----------------
>  arch/x86/xen/xen-ops.h                |  2 ++
>  8 files changed, 13 insertions(+), 28 deletions(-)
>
> diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S
> index 5d8f987a340d..eb1eb7b70f4b 100644
> --- a/arch/x86/ia32/ia32entry.S
> +++ b/arch/x86/ia32/ia32entry.S
> @@ -77,12 +77,6 @@ ENTRY(native_usergs_sysret32)
>         swapgs
>         sysretl
>  ENDPROC(native_usergs_sysret32)
> -
> -ENTRY(native_irq_enable_sysexit)
> -       swapgs
> -       sti
> -       sysexit
> -ENDPROC(native_irq_enable_sysexit)
>  #endif
>
>  /*
> diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h
> index 7549b8b369e4..38a0ff9ef06e 100644
> --- a/arch/x86/include/asm/paravirt_types.h
> +++ b/arch/x86/include/asm/paravirt_types.h
> @@ -160,13 +160,14 @@ struct pv_cpu_ops {
>         u64 (*read_pmc)(int counter);
>         unsigned long long (*read_tscp)(unsigned int *aux);
>
> +#ifdef CONFIG_X86_32
>         /*
>          * Atomically enable interrupts and return to userspace.  This
> -        * is only ever used to return to 32-bit processes; in a
> -        * 64-bit kernel, it's used for 32-on-64 compat processes, but
> -        * never native 64-bit processes.  (Jump, not call.)
> +        * is only used in 32-bit kernels.  64-bit kernels use
> +        * usergs_sysret32 instead.
>          */
>         void (*irq_enable_sysexit)(void);
> +#endif
>
>         /*
>          * Switch to usermode gs and return to 64-bit usermode using
> diff --git a/arch/x86/kernel/asm-offsets.c b/arch/x86/kernel/asm-offsets.c
> index 9f6b9341950f..2d27ebf0aed8 100644
> --- a/arch/x86/kernel/asm-offsets.c
> +++ b/arch/x86/kernel/asm-offsets.c
> @@ -49,7 +49,9 @@ void common(void) {
>         OFFSET(PV_IRQ_irq_disable, pv_irq_ops, irq_disable);
>         OFFSET(PV_IRQ_irq_enable, pv_irq_ops, irq_enable);
>         OFFSET(PV_CPU_iret, pv_cpu_ops, iret);
> +#ifdef CONFIG_X86_32
>         OFFSET(PV_CPU_irq_enable_sysexit, pv_cpu_ops, irq_enable_sysexit);
> +#endif
>         OFFSET(PV_CPU_read_cr0, pv_cpu_ops, read_cr0);
>         OFFSET(PV_MMU_read_cr2, pv_mmu_ops, read_cr2);
>  #endif
> diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
> index 548d25f00c90..7563114d9c3a 100644
> --- a/arch/x86/kernel/paravirt.c
> +++ b/arch/x86/kernel/paravirt.c
> @@ -154,7 +154,9 @@ unsigned paravirt_patch_default(u8 type, u16 clobbers, void *insnbuf,
>                 ret = paravirt_patch_ident_64(insnbuf, len);
>
>         else if (type == PARAVIRT_PATCH(pv_cpu_ops.iret) ||
> +#ifdef CONFIG_X86_32
>                  type == PARAVIRT_PATCH(pv_cpu_ops.irq_enable_sysexit) ||
> +#endif
>                  type == PARAVIRT_PATCH(pv_cpu_ops.usergs_sysret32) ||
>                  type == PARAVIRT_PATCH(pv_cpu_ops.usergs_sysret64))
>                 /* If operation requires a jmp, then jmp */
> @@ -371,7 +373,7 @@ __visible struct pv_cpu_ops pv_cpu_ops = {
>
>         .load_sp0 = native_load_sp0,
>
> -#if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION)
> +#if defined(CONFIG_X86_32)
>         .irq_enable_sysexit = native_irq_enable_sysexit,
>  #endif
>  #ifdef CONFIG_X86_64
> diff --git a/arch/x86/kernel/paravirt_patch_64.c b/arch/x86/kernel/paravirt_patch_64.c
> index a1da6737ba5b..0de21c62c348 100644
> --- a/arch/x86/kernel/paravirt_patch_64.c
> +++ b/arch/x86/kernel/paravirt_patch_64.c
> @@ -49,7 +49,6 @@ unsigned native_patch(u8 type, u16 clobbers, void *ibuf,
>                 PATCH_SITE(pv_irq_ops, save_fl);
>                 PATCH_SITE(pv_irq_ops, irq_enable);
>                 PATCH_SITE(pv_irq_ops, irq_disable);
> -               PATCH_SITE(pv_cpu_ops, irq_enable_sysexit);
>                 PATCH_SITE(pv_cpu_ops, usergs_sysret32);
>                 PATCH_SITE(pv_cpu_ops, usergs_sysret64);
>                 PATCH_SITE(pv_cpu_ops, swapgs);
> diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
> index 81665c9f2132..3797b6b31f95 100644
> --- a/arch/x86/xen/enlighten.c
> +++ b/arch/x86/xen/enlighten.c
> @@ -1267,10 +1267,11 @@ static const struct pv_cpu_ops xen_cpu_ops __initconst = {
>         .read_tscp = native_read_tscp,
>
>         .iret = xen_iret,
> -       .irq_enable_sysexit = xen_sysexit,
>  #ifdef CONFIG_X86_64
>         .usergs_sysret32 = xen_sysret32,
>         .usergs_sysret64 = xen_sysret64,
> +#else
> +       .irq_enable_sysexit = xen_sysexit,
>  #endif
>
>         .load_tr_desc = paravirt_nop,
> diff --git a/arch/x86/xen/xen-asm_64.S b/arch/x86/xen/xen-asm_64.S
> index 985fc3ee0973..a2cabb8bd6bf 100644
> --- a/arch/x86/xen/xen-asm_64.S
> +++ b/arch/x86/xen/xen-asm_64.S
> @@ -47,22 +47,6 @@ ENTRY(xen_iret)
>  ENDPATCH(xen_iret)
>  RELOC(xen_iret, 1b+1)
>
> -/*
> - * sysexit is not used for 64-bit processes, so it's only ever used to
> - * return to 32-bit compat userspace.
> - */
> -ENTRY(xen_sysexit)
> -       pushq $__USER32_DS
> -       pushq %rcx
> -       pushq $X86_EFLAGS_IF
> -       pushq $__USER32_CS
> -       pushq %rdx
> -
> -       pushq $0
> -1:     jmp hypercall_iret
> -ENDPATCH(xen_sysexit)
> -RELOC(xen_sysexit, 1b+1)
> -
>  ENTRY(xen_sysret64)
>         /*
>          * We're already on the usermode stack at this point, but
> diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h
> index 9e195c683549..c20fe29e65f4 100644
> --- a/arch/x86/xen/xen-ops.h
> +++ b/arch/x86/xen/xen-ops.h
> @@ -134,7 +134,9 @@ DECL_ASM(void, xen_restore_fl_direct, unsigned long);
>
>  /* These are not functions, and cannot be called normally */
>  __visible void xen_iret(void);
> +#ifdef CONFIG_X86_32
>  __visible void xen_sysexit(void);
> +#endif
>  __visible void xen_sysret32(void);
>  __visible void xen_sysret64(void);
>  __visible void xen_adjust_exception_frame(void);
> --
> 2.3.0
>



-- 
Andy Lutomirski
AMA Capital Management, LLC
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