linux-kernel - Re: [PATCH 2/3] x86/amd-iommu: Work around S3 BIOS bug

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Message-ID: <20100930202104.GA20495@srcf.ucam.org>
Date:	Thu, 30 Sep 2010 21:21:04 +0100
From:	Matthew Garrett <mjg59@...f.ucam.org>
To:	Joerg Roedel <joerg.roedel@....com>
Cc:	Ingo Molnar <mingo@...e.hu>, iommu@...ts.linux-foundation.org,
	linux-kernel@...r.kernel.org, stable@...nel.org
Subject: Re: [PATCH 2/3] x86/amd-iommu: Work around S3 BIOS bug

On Thu, Sep 23, 2010 at 04:44:48PM +0200, Joerg Roedel wrote:
> +static void iommu_apply_quirks(struct amd_iommu *iommu)
> +{
> +	if (is_rd890_iommu(iommu->dev)) {
> +		pci_write_config_dword(iommu->dev, 0xf0, iommu->cache_cfg[0]);
> +		pci_write_config_dword(iommu->dev, 0xf4, iommu->cache_cfg[1]);
> +		pci_write_config_dword(iommu->dev, 0xf8, iommu->cache_cfg[2]);
> +		pci_write_config_dword(iommu->dev, 0xfc, iommu->cache_cfg[3]);
> +	}
> +}
> +

This doesn't look right. 0xf0-0xff are for indexed register access, so 
what you're doing here is just restoring the last of each of those 
registers that the BIOS programmed - and if the BIOS cleared the 
writable flag afterwards, you're not even doing that.

-- 
Matthew Garrett | mjg59@...f.ucam.org
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