linux-kernel - Re: [PATCH v5 5/8] iommu/amd: copy old trans table from old kernel

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Message-ID: <20160928130136.GA9185@x1.redhat.com>
Date:   Wed, 28 Sep 2016 21:01:36 +0800
From:   Baoquan He <bhe@...hat.com>
To:     Joerg Roedel <joro@...tes.org>
Cc:     iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        kexec@...ts.infradead.org, dyoung@...hat.com, xlpang@...hat.com,
        Vincent.Wan@....com
Subject: Re: [PATCH v5 5/8] iommu/amd: copy old trans table from old kernel

On 09/28/16 at 09:37am, Baoquan He wrote:
> Hi Joerg,
> 
> On 09/20/16 at 02:40pm, Joerg Roedel wrote:
> > > +	if ( !is_pre_enabled) {
> > > +		for_each_iommu(iommu)
> > > +			early_enable_iommu(iommu);
> > > +	} else {
> > > +		if (copy_dev_tables()) {
> > > +			pr_err("Failed to copy DEV table from previous kernel.\n");
> > > +			/*
> > > +			 * If failed to copy dev tables from old kernel, continue to proceed
> > > +			 * as it does in normal kernel.
> > > +			 */
> > > +			for_each_iommu(iommu) {
> > > +				clear_translation_pre_enabled(iommu);
> > > +				early_enable_iommu(iommu);
> > > +			}
> > > +		} else {
> > > +			pr_info("Copied DEV table from previous kernel.\n");
> > > +			for_each_iommu(iommu) {
> > > +				iommu_feature_disable(iommu, CONTROL_CMDBUF_EN);
> > > +		                iommu_feature_disable(iommu, CONTROL_EVT_LOG_EN);
> > 
> > Could you move that into new helpers (iommu_disable_command_buffer...)?
> 
> Did you mean wraping iommu_feature_disable(iommu, CONTROL_CMDBUF_EN) into a
> helper function like iommu_disable_command_buffer(), and wraping
> iommu_feature_disable(iommu, CONTROL_EVT_LOG_EN) into
> iommu_disable_event_buffer()?
> 
> I retest with not disabling command buffer and event log here, it works
> on amd iommu v1 and v2 systems. So if I understand your comment
> correctly, there's no need to add "iommu_feature_disable(iommu,
> CONTROL_CMDBUF_EN)"  and "iommu_feature_disable(iommu,
> CONTROL_EVT_LOG_EN)" here. I remember I added them here because more
> IO_PAGE_FAULT messages are printed without them. But now it seems not to
> related to them. So I will remove above two lines of code.

Oh, sorry, please ignore this. It will print many lines of below message
if do not disable cmd buffer and event log here.

[    0.455642] AMD-Vi: Completion-Wait loop timed out