linux-kernel - Re: [PATCH] KVM x86: Handle hypercalls for assigned PCI devices

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Message-Id: <200805011848.29363.amit.shah@qumranet.com>
Date:	Thu, 1 May 2008 18:48:28 +0530
From:	Amit Shah <amit.shah@...ranet.com>
To:	Glauber Costa <gcosta@...hat.com>
Cc:	kvm-devel@...ts.sourceforge.net,
	virtualization@...ts.linux-foundation.org, muli@...ibm.com,
	BENAMI@...ibm.com, chrisw@...hat.com, dor.laor@...ranet.com,
	allen.m.kay@...el.com, avi@...ranet.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KVM x86: Handle hypercalls for assigned PCI devices

On Tuesday 29 April 2008 21:28:51 Amit Shah wrote:
> On Tuesday 29 April 2008 20:14:16 Glauber Costa wrote:
> > Amit Shah wrote:

> > > +	if (find_pci_pt_dev(&vcpu->kvm->arch.pci_pt_dev_head,
> > > +			    &pci_pt_info, 0, KVM_PT_SOURCE_ASSIGN))
> > > +		r++; /* We have assigned the device */
> > > +
> > > +	kunmap(host_page);
> >
> > better use atomic mappings here.
>
> We can't use atomic mappings for guest pages. They can be swapped out.

Actually you were right: there's no sleeping call here after doing the 
mapping. I've updated this call with kmap_atomic.

The other function that uses kmap can't be converted since we continue to map 
several pages in a loop (depending on the length of the DMA region) and hence 
can't use kmap_atomic there.
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