From mboxrd@z Thu Jan  1 00:00:00 1970
From: Anthony Liguori <anthony@codemonkey.ws>
Subject: Re: [PATCH 5/7] KVM/userspace: Device Assignment: Support for assigning
 PCI devices to guests
Date: Tue, 23 Sep 2008 14:18:51 -0500
Message-ID: <48D9411B.8040905@codemonkey.ws>
References: <1222181695-23418-1-git-send-email-amit.shah@redhat.com> <1222181695-23418-2-git-send-email-amit.shah@redhat.com> <1222181695-23418-3-git-send-email-amit.shah@redhat.com> <1222181695-23418-4-git-send-email-amit.shah@redhat.com> <1222181695-23418-5-git-send-email-amit.shah@redhat.com> <1222181695-23418-6-git-send-email-amit.shah@redhat.com> <48D919A8.8040409@codemonkey.ws> <20080923183207.GA6922@il.ibm.com>
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Cc: Amit Shah <amit.shah@redhat.com>, avi@redhat.com,
	kvm@vger.kernel.org, Ben-Ami Yassour1 <BENAMI@il.ibm.com>,
	weidong.han@intel.com, allen.m.kay@intel.com
To: Muli Ben-Yehuda <muli@il.ibm.com>
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Muli Ben-Yehuda wrote:
> On Tue, Sep 23, 2008 at 11:30:32AM -0500, Anthony Liguori wrote:
>   
>>> +		+ (addr - r_access->e_physbase);
>>> +
>>> +	if (r_access->debug & DEVICE_ASSIGNMENT_DEBUG_PIO) {
>>> +		fprintf(stderr, "%s: r_pio=%08x e_physbase=%08x"
>>> +			" r_virtbase=%08lx value=%08x\n",
>>> +			__func__, r_pio, (int)r_access->e_physbase,
>>> +			(unsigned long)r_access->r_virtbase, value);
>>> +	}
>>> +	iopl(3);
>>> +	outb(value, r_pio);
>>>   
>>>       
>> The formatting is wrong for this entire file.  Also, you shouldn't
>> have device specific debug.  Should probably error check iopl(3).
>> It's not necessary to call it every time you do an outb, just once
>> when initialized.
>>     
>
> We tried that at first, but ran into cases where even after iopl()
> ran, pio's from qemu still failed. Does qemu do anything to drop
> iopl() privileges? In any case calling iopl() unconditionally on every
> pio fixed it, but is obviously not the right long-term solution.
>   

Make sure you issue iopl() before any of the VCPU threads are spawned.  
Otherwise, you may be running into issues when something other than 
VCPU-0 is doing PIO/MMIO and you haven't iopl()'d for that thread.

Regards,

Anthony Liguori

> Cheers,
> Muli
>