Re: [Xen-devel] [PATCH V2] x86/altp2m: Hypercall to set altp2m view visibility

From: Alexandru Stefan ISAILA <aisaila@bitdefender.com>
To: Jan Beulich <jbeulich@suse.com>
Cc: "Kevin Tian" <kevin.tian@intel.com>,
	"Stefano Stabellini" <sstabellini@kernel.org>,
	"Julien Grall" <julien@xen.org>, "Wei Liu" <wl@xen.org>,
	"Konrad Rzeszutek Wilk" <konrad.wilk@oracle.com>,
	"George Dunlap" <George.Dunlap@eu.citrix.com>,
	"Andrew Cooper" <andrew.cooper3@citrix.com>,
	"Ian Jackson" <ian.jackson@eu.citrix.com>,
	"Jun Nakajima" <jun.nakajima@intel.com>,
	"xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>,
	"Roger Pau Monné" <roger.pau@citrix.com>
Subject: Re: [Xen-devel] [PATCH V2] x86/altp2m: Hypercall to set altp2m view visibility
Date: Tue, 18 Feb 2020 14:42:30 +0000	[thread overview]
Message-ID: <1fd4b6fc-f380-ac8e-4b3d-394d48885fb7@bitdefender.com> (raw)
In-Reply-To: <695f304c-2968-66fe-5a33-14c81d980d18@bitdefender.com>

>>> --- a/xen/arch/x86/mm/hap/hap.c
>>> +++ b/xen/arch/x86/mm/hap/hap.c
>>> @@ -488,8 +488,17 @@ int hap_enable(struct domain *d, u32 mode)
>>>                goto out;
>>>            }
>>>    
>>> +        if ( (d->arch.altp2m_working_eptp = alloc_xenheap_page()) == NULL )
>>> +        {
>>> +            rv = -ENOMEM;
>>> +            goto out;
>>> +        }
>>
>> Isn't there a pre-existing error handling issue here which you
>> widen, in that later encountered errors don't cause clean up
>> of what had already succeeded before?
> 
> It seems non of the errors perform a cleanup. It might be better to have
> a general cleanup done at "out:" if ( !rv ) and then check what should
> be "p2m_teardown()" or "free_xenheap_page()".
> 

I've looked around for this and it is handled in arch_domain_create().
If hvm_domain_initialise() fails then paging_final_teardown() is called 
and in the end hap_final_teardown() takes care of cleaning up.

Alex
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