linux-kernel - Re: [PATCH 2/2] KVM, Fix QEMU-KVM is killed by guest SRAO MCE

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Message-ID: <4BD6AEC7.5020609@redhat.com>
Date:	Tue, 27 Apr 2010 12:30:47 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Huang Ying <ying.huang@...el.com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Andi Kleen <andi@...stfloor.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"masbock@...ux.vnet.ibm.com" <masbock@...ux.vnet.ibm.com>,
	kvm@...r.kernel.org
Subject: Re: [PATCH 2/2] KVM, Fix QEMU-KVM is killed by guest SRAO MCE

On 04/27/2010 12:25 PM, Huang Ying wrote:
>
>
>> On 04/27/2010 10:04 AM, Huang Ying wrote:
>>      
>>> +static void kvm_send_hwpoison_signal(struct kvm *kvm, gfn_t gfn)
>>> +{
>>> +	char buf[1];
>>> +	void __user *hva;
>>> +	int r;
>>> +
>>> +	/* Touch the page, so send SIGBUS */
>>> +	hva = (void __user *)gfn_to_hva(kvm, gfn);
>>> +	r = copy_from_user(buf, hva, 1);
>>>
>>>        
>> No error check?  What will a copy_from_user() of poisoned page expected
>> to return?
>>
>> Best to return -EFAULT on failure for consistency.
>>      
> Just want to use the side effect of copy_from_user, SIGBUS will be sent
> to current process because the page touched is marked as poisoned. That
> is, failure is expected, so the return value is not checked.
>    

What if the failure doesn't happen?  Say, someone mmap()ed over the page.

btw, better to use (void)copy_from_user(...) instead to avoid the 
initialized but not used warning the compiler may generate.


-- 
error compiling committee.c: too many arguments to function

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