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RE: [Xen-devel] [PATCH 0/5] Add MSI support to XEN

To: "Neil Turton" <nturton@xxxxxxxxxxxxxx>
Subject: RE: [Xen-devel] [PATCH 0/5] Add MSI support to XEN
From: "Shan, Haitao" <haitao.shan@xxxxxxxxx>
Date: Thu, 3 Apr 2008 20:11:55 +0800
Cc: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>, xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, "Li, Xin B" <xin.b.li@xxxxxxxxx>, "Tian, Kevin" <kevin.tian@xxxxxxxxx>, "Jiang, Yunhong" <yunhong.jiang@xxxxxxxxx>
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Thread-topic: [Xen-devel] [PATCH 0/5] Add MSI support to XEN
Hi, Neil

Thanks for trying the patches. The problem is caused by incompatibility between 
Xen and Dom0 kernel.
Pci_vector_resources is to calculate available vectors. Xen assigns vector by 
start with vector 0x20 and offset = 0. This will confuse the code in 
Maybe we should replace the function with a hypercall to acquire the number of 
available vectors. 
How do you think about it, Keir?

Shan Haitao

-----Original Message-----
From: Neil Turton [mailto:nturton@xxxxxxxxxxxxxx] 
Sent: 2008年4月2日 22:56
To: Shan, Haitao
Cc: Keir Fraser; xen-devel; Tian, Kevin; Jiang, Yunhong; Li, Xin B
Subject: Re: [Xen-devel] [PATCH 0/5] Add MSI support to XEN

I tried this patch and MSI seems to work fine with a driver in DOM0.  It
didn't work with MSI-X though because pci_vector_resources returned 8
and I have 10 MSI capable devices in the machine.  I've only got 6
Phys-irq interrupts listed in /proc/interrupts so I'd expect there to be
more vectors free.  I applied the debugging patch below and got the
following output.

diff -r 9bb373519b68 arch/i386/pci/irq-xen.c
--- a/arch/i386/pci/irq-xen.c   Tue Apr 01 14:15:23 2008 +0100
+++ b/arch/i386/pci/irq-xen.c   Wed Apr 02 13:19:05 2008 +0100
@@ -1192,6 +1192,7 @@ int pci_vector_resources(int last, int n
        int offset = (last % 8);

        while (next < FIRST_SYSTEM_VECTOR) {
+               printk("next=%d count=%d\n", next, count);
                next += 8;
 #ifdef CONFIG_X86_64
                if (next == IA32_SYSCALL_VECTOR)

[pci_vector_resources(176, 1) called]
next=176 count=1
next=184 count=2
next=192 count=3
next=200 count=4
next=208 count=5
next=216 count=6
next=224 count=7
next=232 count=8
[pci_vector_resources returned 8]

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