linux-kernel - Re: [PATCH] IR: Fix kernel hang if interrupt remapping disable in BIOS

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Date:	Wed, 9 Sep 2009 12:42:22 +0400
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	Youquan Song <youquan.song@...el.com>
Cc:	mingo@...e.hu, hpa@...or.com, tglx@...utronix.de,
	linux-kernel@...r.kernel.org, dwmw2@...radead.org,
	Suresh Siddha <suresh.b.siddha@...el.com>
Subject: Re: [PATCH] IR: Fix kernel hang if interrupt remapping disable in 
	BIOS

On 9/9/09, Youquan Song <youquan.song@...el.com> wrote:
> BIOS clear DMAR table INTR_REMAP flag to disable interrupt remapping.
> Current
> kernel only check interrupt remapping(IR) flag in DRHD's extended capability
> register to decide interrupt remapping support or not. But IR flag will not
> change when BIOS disable/enable interrupt remapping.
>
> When user disable interrupt remapping in BIOS or BIOS often defaultly
> disable
> interrupt remapping feature when BIOS is not mature.Though BIOS disable
> interrupt remapping but intr_remapping_supported function will always report
> to OS support interrupt remapping if VT-d2 chipset populated. On this
> cases, kernel will continue enable interrupt remapping and result kernel
> panic.
> This bug exist on almost all platforms with interrupt remapping support.
>
>
> This patch add DMAR table INTR_REMAP flag check before enable interrup
> remapping
>
> Signed-off-by: Youquan Song <youquan.song@...el.com>
> ---
>

thanks, Youquan!

> diff --git a/drivers/pci/dmar.c b/drivers/pci/dmar.c
> index a8a4383..d943e95 100644
> --- a/drivers/pci/dmar.c
> +++ b/drivers/pci/dmar.c
> @@ -1302,3 +1302,13 @@ int dmar_reenable_qi(struct intel_iommu *iommu)
>
>  	return 0;
>  }
> +
> +/*
> + * Check interrupt remapping support in DMAR table description.
> + */
> +int dmar_ir_support(void)
> +{
> +	struct acpi_table_dmar *dmar;
> +	dmar = (struct acpi_table_dmar *)dmar_tbl;
> +	return dmar->flags & 0x1;
> +}
> diff --git a/drivers/pci/intr_remapping.c b/drivers/pci/intr_remapping.c
> index ebfa47b..ac06514 100644
> --- a/drivers/pci/intr_remapping.c
> +++ b/drivers/pci/intr_remapping.c
> @@ -611,6 +611,9 @@ int __init intr_remapping_supported(void)
>  	if (disable_intremap)
>  		return 0;
>
> +	if (!dmar_ir_support())
> +		return 0;
> +
>  	for_each_drhd_unit(drhd) {
>  		struct intel_iommu *iommu = drhd->iommu;
>
> diff --git a/include/linux/intel-iommu.h b/include/linux/intel-iommu.h
> index 482dc91..4f0a72a 100644
> --- a/include/linux/intel-iommu.h
> +++ b/include/linux/intel-iommu.h
> @@ -360,4 +360,6 @@ extern void qi_flush_dev_iotlb(struct intel_iommu
> *iommu, u16 sid, u16 qdep,
>
>  extern int qi_submit_sync(struct qi_desc *desc, struct intel_iommu *iommu);
>
> +extern int dmar_ir_support(void);
> +
>  #endif
>
--
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