linux-kernel - Re: [PATCH] KVM PV Guest: Implement paravirtualized DMA

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Message-ID: <87od7shjnv.fsf@basil.nowhere.org>
Date:	Tue, 29 Apr 2008 15:31:32 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Amit Shah <amit.shah@...ranet.com>
Cc:	kvm-devel@...ts.sourceforge.net, chrisw@...hat.com,
	allen.m.kay@...el.com, linux-kernel@...r.kernel.org,
	gcosta@...hat.com, avi@...ranet.com,
	virtualization@...ts.linux-foundation.org, BENAMI@...ibm.com
Subject: Re: [PATCH] KVM PV Guest: Implement paravirtualized DMA

Amit Shah <amit.shah@...ranet.com> writes:
> +
> +static struct page *page;
> +static unsigned long page_gfn;
Bad variable names

> +
> +const struct dma_mapping_ops *orig_dma_ops;

I suspect real dma ops stacking will need some further thought than
your simple hacks
> +
> +	match = find_matching_pt_dev(&pt_devs_head, &pv_pci_info);
> +	if (match) {
> +		r = match->is_pv;
> +		goto out;
> +	}
> +
> +	memcpy(page_address(page), &pv_pci_info, sizeof(pv_pci_info));

Note that on 32bit page_address() might be not mapped.


> +
> +	npages = get_order(size) + 1;

Are you sure that's correct? It looks quite bogus. order is a 2 logarithm,
normally npages = 1 << order

if you want  npages from order the correct  need 1 << order

Haven't read further, but to be honest the code doesn't seem to be anywhere
near merging quality.

-Andi

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