netdev - RE: [PATCH 6/8] iommu/intel: Add a gfp parameter to alloc_pgtable

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Date:   Wed, 18 Jan 2023 01:18:18 +0000
From:   "Tian, Kevin" <kevin.tian@...el.com>
To:     Jason Gunthorpe <jgg@...dia.com>
CC:     Lu Baolu <baolu.lu@...ux.intel.com>,
        Joerg Roedel <joro@...tes.org>,
        Matthew Rosato <mjrosato@...ux.ibm.com>,
        Robin Murphy <robin.murphy@....com>,
        Alex Williamson <alex.williamson@...hat.com>,
        "ath10k@...ts.infradead.org" <ath10k@...ts.infradead.org>,
        "ath11k@...ts.infradead.org" <ath11k@...ts.infradead.org>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>,
        "linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
        "linux-remoteproc@...r.kernel.org" <linux-remoteproc@...r.kernel.org>,
        "linux-s390@...r.kernel.org" <linux-s390@...r.kernel.org>,
        "linux-stm32@...md-mailman.stormreply.com" 
        <linux-stm32@...md-mailman.stormreply.com>,
        "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
        "linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "nouveau@...ts.freedesktop.org" <nouveau@...ts.freedesktop.org>,
        Niklas Schnelle <schnelle@...ux.ibm.com>,
        "virtualization@...ts.linux-foundation.org" 
        <virtualization@...ts.linux-foundation.org>
Subject: RE: [PATCH 6/8] iommu/intel: Add a gfp parameter to
 alloc_pgtable_page()

> From: Jason Gunthorpe <jgg@...dia.com>
> Sent: Tuesday, January 17, 2023 9:30 PM
> 
> On Tue, Jan 17, 2023 at 03:35:08AM +0000, Tian, Kevin wrote:
> > > From: Jason Gunthorpe <jgg@...dia.com>
> > > Sent: Saturday, January 7, 2023 12:43 AM
> > >
> > > @@ -2676,7 +2676,7 @@ static int copy_context_table(struct
> intel_iommu
> > > *iommu,
> > >  			if (!old_ce)
> > >  				goto out;
> > >
> > > -			new_ce = alloc_pgtable_page(iommu->node);
> > > +			new_ce = alloc_pgtable_page(iommu->node,
> > > GFP_KERNEL);
> >
> > GFP_ATOMIC
> 
> Can't be:
> 
> 			old_ce = memremap(old_ce_phys, PAGE_SIZE,
> 					MEMREMAP_WB);
> 			if (!old_ce)
> 				goto out;
> 
> 			new_ce = alloc_pgtable_page(iommu->node,
> GFP_KERNEL);
> 			if (!new_ce)
> 
> memremap() is sleeping.
> 
> And the only caller is:
> 
> 	ctxt_tbls = kcalloc(ctxt_table_entries, sizeof(void *), GFP_KERNEL);
> 	if (!ctxt_tbls)
> 		goto out_unmap;
> 
> 	for (bus = 0; bus < 256; bus++) {
> 		ret = copy_context_table(iommu, &old_rt[bus],
> 					 ctxt_tbls, bus, ext);
> 

Yes, but the patch description says "Push the GFP_ATOMIC to all
callers." implying it's purely a refactoring w/o changing those
semantics.

I'm fine with doing this change in this patch, but it should worth
a clarification in the patch description.