linux-kernel - Re: [PATCH] x86: enable x2apic early at the first point

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Date:	Thu, 19 Feb 2009 14:13:32 -0800
From:	Suresh Siddha <suresh.b.siddha@...el.com>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86: enable x2apic early at the first point

On Thu, 2009-02-19 at 13:50 -0800, Yinghai Lu wrote:
> Impact: fix bug.
> 
> otherwise will get panic from early_acpi_boot_init()
> also make disable_x2apic global, so could use it it x2_apic_xxx.c
> and can get warning if preenabled system using nox2apic.
> 
> Signed-off-by: Yinghai Lu <yinghai@...nel.org>
> 
> ---
>  arch/x86/kernel/apic/apic.c           |    3 +--
>  arch/x86/kernel/apic/x2apic_cluster.c |    5 ++++-
>  arch/x86/kernel/apic/x2apic_phys.c    |    5 ++++-
>  arch/x86/kernel/apic/x2apic_uv_x.c    |    4 +++-
>  drivers/pci/dmar.c                    |    3 ++-
>  5 files changed, 14 insertions(+), 6 deletions(-)
> 
> Index: linux-2.6/arch/x86/kernel/apic/x2apic_cluster.c
> ===================================================================
> --- linux-2.6.orig/arch/x86/kernel/apic/x2apic_cluster.c
> +++ linux-2.6/arch/x86/kernel/apic/x2apic_cluster.c
> @@ -14,8 +14,11 @@ DEFINE_PER_CPU(u32, x86_cpu_to_logical_a
> 
>  static int x2apic_acpi_madt_oem_check(char *oem_id, char *oem_table_id)
>  {
> -       if (cpu_has_x2apic)
> +       if (cpu_has_x2apic && !disable_x2apic) {
> +               x2apic = 1;
> +               enable_x2apic();

Yinghai, I also ran into couple of x2apic issues on the latest tip and
this issue is one of them. I don't like this patch mainly because we are
enabling x2apic mode in the cpu, with out checking the intr-remapping
support. We should fall back to xapic mode (in a clean fashion) if there
is any issue with intr-remapping. So I am planning to post another patch
to fix this early hang issue that we both encountered.

thanks,
suresh

>                 return 1;
> +       }
> 
>         return 0;
>  }
> Index: linux-2.6/arch/x86/kernel/apic/x2apic_phys.c
> ===================================================================
> --- linux-2.6.orig/arch/x86/kernel/apic/x2apic_phys.c
> +++ linux-2.6/arch/x86/kernel/apic/x2apic_phys.c
> @@ -21,8 +21,11 @@ early_param("x2apic_phys", set_x2apic_ph
> 
>  static int x2apic_acpi_madt_oem_check(char *oem_id, char *oem_table_id)
>  {
> -       if (cpu_has_x2apic && x2apic_phys)
> +       if (cpu_has_x2apic && !disable_x2apic && x2apic_phys) {
> +               x2apic = 1;
> +               enable_x2apic();
>                 return 1;
> +       }
> 
>         return 0;
>  }
> Index: linux-2.6/arch/x86/kernel/apic/x2apic_uv_x.c
> ===================================================================
> --- linux-2.6.orig/arch/x86/kernel/apic/x2apic_uv_x.c
> +++ linux-2.6/arch/x86/kernel/apic/x2apic_uv_x.c
> @@ -41,8 +41,10 @@ static int uv_acpi_madt_oem_check(char *
>                         uv_system_type = UV_LEGACY_APIC;
>                 else if (!strcmp(oem_table_id, "UVX"))
>                         uv_system_type = UV_X2APIC;
> -               else if (!strcmp(oem_table_id, "UVH")) {
> +               else if (!strcmp(oem_table_id, "UVH") && !disable_x2apic) {
>                         uv_system_type = UV_NON_UNIQUE_APIC;
> +                       x2apic = 1;
> +                       enable_x2apic();
>                         return 1;
>                 }
>         }
> Index: linux-2.6/arch/x86/kernel/apic/apic.c
> ===================================================================
> --- linux-2.6.orig/arch/x86/kernel/apic/apic.c
> +++ linux-2.6/arch/x86/kernel/apic/apic.c
> @@ -116,11 +116,10 @@ __setup("apicpmtimer", setup_apicpmtimer
>  int x2apic;
>  /* x2apic enabled before OS handover */
>  static int x2apic_preenabled;
> -static int disable_x2apic;
> +int disable_x2apic;
>  static __init int setup_nox2apic(char *str)
>  {
>         disable_x2apic = 1;
> -       setup_clear_cpu_cap(X86_FEATURE_X2APIC);
>         return 0;
>  }
>  early_param("nox2apic", setup_nox2apic);
> Index: linux-2.6/drivers/pci/dmar.c
> ===================================================================
> --- linux-2.6.orig/drivers/pci/dmar.c
> +++ linux-2.6/drivers/pci/dmar.c
> @@ -472,7 +472,8 @@ void __init detect_intel_iommu(void)
>                  * is added, we will not need this any more.
>                  */
>                 dmar = (struct acpi_table_dmar *) dmar_tbl;
> -               if (ret && cpu_has_x2apic && dmar->flags & 0x1)
> +               if (ret && cpu_has_x2apic && !disable_x2apic &&
> +                        dmar->flags & 0x1)
>                         printk(KERN_INFO
>                                "Queued invalidation will be enabled to support "
>                                "x2apic and Intr-remapping.\n");

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