This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
Home Products Support Community News


[Xen-devel] Re: Accessing PCI BAR space directly from XEN hypervisor

To: xen-devel@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-devel] Re: Accessing PCI BAR space directly from XEN hypervisor
From: veerasena reddy <veeruyours@xxxxxxxxx>
Date: Tue, 14 Jun 2011 08:55:15 +0530
Delivery-date: Mon, 13 Jun 2011 20:26:05 -0700
Dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:in-reply-to:references:date :message-id:subject:from:to:content-type; bh=DW3VXbd1IKpgsbt6Ywu6j1t1AHchPBvqyzft7f+FOvA=; b=d4JHNxIkELorCs3IOVGait4C/grFE9QXVA6LoQJdmcOkxJ7DhDXATQnlPhM6DUQ4AL FgT7zBMtbzlPkYNE9deixGrsaSjTuZfhrwL6ICssRn9LXCaacpNy38YjYXpOC/Zf8VEQ wQ3Icx0ILJMtqw3dDKKZeBD9I10vIYV3bTmvw=
Domainkey-signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; b=CDAs9LytrMFGa16OQMuW7cMdLPN8beAiVunux71ldLbISWhj+/oOh6OrcoScdpKLjT 7EOQuep4lm8X4TC1ceYwwQyOy7fcKfUyAfoBJam9IX1N4DpgVWGXsSN8e+uC3G7aZrbN wRDHO2xFS2eWtTig12uAZCflvnc891njYiV7c=
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to: <BANLkTim_htK=MnD+iShPPNKO4iOkY6gf3A@xxxxxxxxxxxxxx>
List-help: <mailto:xen-devel-request@lists.xensource.com?subject=help>
List-id: Xen developer discussion <xen-devel.lists.xensource.com>
List-post: <mailto:xen-devel@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
References: <BANLkTim_htK=MnD+iShPPNKO4iOkY6gf3A@xxxxxxxxxxxxxx>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx

Can someone please throw some light on this

Thanks in advance.

On Mon, Jun 13, 2011 at 2:24 PM, veerasena reddy <veeruyours@xxxxxxxxx> wrote:

I am doing an experiment to see if I can get more throughput by moving the Tx ring update and doorbell ring mechanism to hypervisor and provide a hypercall to HVM Guest. When there is a Tx packet ready, the HVM guest invokes the hypercall along with the packet address as argument. The hypercall function will write the packet address to the Tx ring and rings the doorbell directly without involving dom0.

AS part of this, i need to access IO Memory BAR region of the PCI network device from XEN hypervisor (hypercall handler). For this, i tried converting the BAR Physical address (captured from lspci as shown below) of the PCI device to MFN, but got all F's (invalid entry). Even pfn_valid(0xf0904000) failed on this address. Where as I could successfully map a dom0 page (allocated using vmalloc()) and access in hypervisor using map_domain_page(mfn).

Could any one please suggest how to access the BAR regions of a PCI device from hypervisor? how to do mapping and read/write operations?

Also, Could you please explain the difference between mapping locally allocated pages and PCI BAR memory of dom0 in hypervisor?

Thanks in advance.

[root@fc13 xen]# lspci -vvs 09:00.0
09:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168B PCI Express Gigabit Ethernet controller (rev 03)
    Subsystem: Lenovo Device 2131
    Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR+ FastB2B- DisINTx+
    Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
    Latency: 0, Cache Line Size: 64 bytes
    Interrupt: pin A routed to IRQ 1247
    Region 0: I/O ports at 4000 [size=256]
    Region 2: Memory at f0904000 (64-bit, prefetchable) [size=4K]
    Region 4: Memory at f0900000 (64-bit, prefetchable) [size=16K]
    [virtual] Expansion ROM at f0920000 [disabled] [size=128K]

Xen-devel mailing list
<Prev in Thread] Current Thread [Next in Thread>