Re: [PATCH v2] x86, vt-d: enable x2apic opt out

[Youquan Song]

The path has been verified from customer platform and it works well.
This patch is also desirable from Linux OSV distributions.
please take it and get it into 2.6.40 merge window.

Thanks
-Youquan


On Thu, Apr 14, 2011 at 03:06:23PM +0800, Youquan Song wrote:
> New version of VT-d2 specification (http://download.intel.com/technology
> /computing/vptech/Intel(r)_VT_for_Direct_IO.pdf) includes a new feature that 
> provide firmware a way to request system software to opt out of enable x2APIC
> mode. DMAR ACPI table newly define flags.1 bit: x2APIC_OPT_OUT which is set to
> request System software opt out xAPIC mode if flags.0 bit:INTR_REMAP is also
> set.
> 
> This patch enable the feature. Also re-define x2apic_supported() to address
> platform x2apic support needs 1)processor has x2apic capability 2)interrupt
> remapping support 3)firmware does not request opt-out.
> 
> Signed-off-by: Youquan Song <youquan.song@xxxxxxxxx>
> Reviewed-by: Kay, Allen M <allen.m.kay@xxxxxxxxx>
> ---
>  arch/x86/include/asm/apic.h |    2 --
>  arch/x86/kernel/apic/apic.c |   13 +++++++++----
>  drivers/pci/dmar.c          |   28 ++++++++++++++++++++++++++--
>  include/linux/dmar.h        |    3 +++
>  include/linux/intel-iommu.h |    4 ++++
>  5 files changed, 42 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h
> index 3c89694..aa3fc82 100644
> --- a/arch/x86/include/asm/apic.h
> +++ b/arch/x86/include/asm/apic.h
> @@ -192,7 +192,6 @@ static inline int x2apic_enabled(void)
>  	return 0;
>  }
>  
> -#define x2apic_supported()	(cpu_has_x2apic)
>  static inline void x2apic_force_phys(void)
>  {
>  	x2apic_phys = 1;
> @@ -213,7 +212,6 @@ static inline void x2apic_force_phys(void)
>  }
>  
>  #define	x2apic_preenabled 0
> -#define	x2apic_supported()	0
>  #endif
>  
>  extern void enable_IR_x2apic(void);
> diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
> index 76b96d7..6c96c45 100644
> --- a/arch/x86/kernel/apic/apic.c
> +++ b/arch/x86/kernel/apic/apic.c
> @@ -1449,11 +1449,11 @@ void __init enable_IR_x2apic(void)
>  {
>  	unsigned long flags;
>  	struct IO_APIC_route_entry **ioapic_entries = NULL;
> -	int ret, x2apic_enabled = 0;
> +	int ret = 0, x2apic_enabled = 0;
>  	int dmar_table_init_ret;
>  
>  	dmar_table_init_ret = dmar_table_init();
> -	if (dmar_table_init_ret && !x2apic_supported())
> +	if (dmar_table_init_ret && !cpu_has_x2apic)
>  		return;
>  
>  	ioapic_entries = alloc_ioapic_entries();
> @@ -1465,6 +1465,7 @@ void __init enable_IR_x2apic(void)
>  	ret = save_IO_APIC_setup(ioapic_entries);
>  	if (ret) {
>  		pr_info("Saving IO-APIC state failed: %d\n", ret);
> +		ret = 0;
>  		goto out;
>  	}
>  
> @@ -1491,7 +1492,8 @@ void __init enable_IR_x2apic(void)
>  		x2apic_force_phys();
>  	}
>  
> -	x2apic_enabled = 1;
> +	if (x2apic_supported())
> +		x2apic_enabled = 1;
>  
>  	if (x2apic_supported() && !x2apic_mode) {
>  		x2apic_mode = 1;
> @@ -1514,8 +1516,11 @@ out:
>  
>  	if (x2apic_preenabled)
>  		panic("x2apic: enabled by BIOS but kernel init failed.");
> -	else if (cpu_has_x2apic)
> +	else if (!ret && cpu_has_x2apic) /* IR enabling failed */
>  		pr_info("Not enabling x2apic, Intr-remapping init failed.\n");
> +	else if (!x2apic_supported() && cpu_has_x2apic)
> +		pr_info("Not enabling x2apic, firmware requests OS opt-out "
> +			  "x2apic.\n");
>  }
>  
>  #ifdef CONFIG_X86_64
> diff --git a/drivers/pci/dmar.c b/drivers/pci/dmar.c
> index 09933eb..a35dca9 100644
> --- a/drivers/pci/dmar.c
> +++ b/drivers/pci/dmar.c
> @@ -705,7 +705,7 @@ int __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 && x2apic_supported() && dmar->flags & DMAR_INTR_REMAP)
>  			printk(KERN_INFO
>  			       "Queued invalidation will be enabled to support "
>  			       "x2apic and Intr-remapping.\n");
> @@ -1461,6 +1461,30 @@ int __init dmar_ir_support(void)
>  	dmar = (struct acpi_table_dmar *)dmar_tbl;
>  	if (!dmar)
>  		return 0;
> -	return dmar->flags & 0x1;
> +	return dmar->flags & DMAR_INTR_REMAP;
>  }
> +
> +/*
> + * Check if the platform support x2apic
> + * three necessary conditions:
> + * a. processor support x2apic
> + * b. interrupt remapping support
> + * c. when interrupt reamapping support,bit of x2APIC_OPT_OUT at "DMAR flags"
> + *  is not set which means firmware does not tell OS opt out x2apic
> + */
> +int __init x2apic_supported(void)
> +{
> +	struct acpi_table_dmar *dmar;
> +	unsigned int flags = 0;
> +
> +	if (!cpu_has_x2apic)
> +		return 0;
> +
> +	dmar = (struct acpi_table_dmar *)dmar_tbl;
> +	if (!dmar)
> +		return 0;
> +	flags = DMAR_INTR_REMAP | DMAR_X2APIC_OPT_OUT;
> +	return ((dmar->flags & flags) == DMAR_INTR_REMAP);
> +}
> +
>  IOMMU_INIT_POST(detect_intel_iommu);
> diff --git a/include/linux/dmar.h b/include/linux/dmar.h
> index 7b776d7..73c9bff 100644
> --- a/include/linux/dmar.h
> +++ b/include/linux/dmar.h
> @@ -228,8 +228,11 @@ struct dmar_atsr_unit {
>  };
>  
>  extern int intel_iommu_init(void);
> +extern int x2apic_supported(void);
> +
>  #else /* !CONFIG_DMAR: */
>  static inline int intel_iommu_init(void) { return -ENODEV; }
> +static inline int x2apic_supported(void) { return 0; }
>  #endif /* CONFIG_DMAR */
>  
>  #endif /* __DMAR_H__ */
> diff --git a/include/linux/intel-iommu.h b/include/linux/intel-iommu.h
> index 9310c69..2d086e5 100644
> --- a/include/linux/intel-iommu.h
> +++ b/include/linux/intel-iommu.h
> @@ -29,6 +29,10 @@
>  #include <asm/cacheflush.h>
>  #include <asm/iommu.h>
>  
> +/* DMAR Flags bits */
> +#define DMAR_INTR_REMAP 0x1
> +#define DMAR_X2APIC_OPT_OUT 0x2
> +
>  /*
>   * Intel IOMMU register specification per version 1.0 public spec.
>   */
> -- 
> 1.6.4.2
> 
> 
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