linux-kernel - Re: [PATCH v10 16/50] x86/sev: Introduce snp leaked pages list

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Message-ID: <f0dc32ea-3b77-1e9e-42fd-3f115c001f7c@amd.com>
Date:   Fri, 8 Dec 2023 14:54:14 -0600
From:   "Kalra, Ashish" <ashish.kalra@....com>
To:     Borislav Petkov <bp@...en8.de>, Michael Roth <michael.roth@....com>
Cc:     kvm@...r.kernel.org, linux-coco@...ts.linux.dev,
        linux-mm@...ck.org, linux-crypto@...r.kernel.org, x86@...nel.org,
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Subject: Re: [PATCH v10 16/50] x86/sev: Introduce snp leaked pages list

On 12/6/2023 2:42 PM, Borislav Petkov wrote:
> On Mon, Oct 16, 2023 at 08:27:45AM -0500, Michael Roth wrote:
>> +	spin_lock(&snp_leaked_pages_list_lock);
>> +	while (npages--) {
>> +		/*
>> +		 * Reuse the page's buddy list for chaining into the leaked
>> +		 * pages list. This page should not be on a free list currently
>> +		 * and is also unsafe to be added to a free list.
>> +		 */
>> +		list_add_tail(&page->buddy_list, &snp_leaked_pages_list);
>> +		sev_dump_rmpentry(pfn);
>> +		pfn++;
>> +	}
>> +	spin_unlock(&snp_leaked_pages_list_lock);
>> +	atomic_long_inc(&snp_nr_leaked_pages);
> 
> How is this supposed to count?
> 
> You're leaking @npages as the function's parameter but are incrementing
> snp_nr_leaked_pages only once?
> 
> Just make it a bog-normal unsigned long and increment it inside the
> locked section.
> 
> Or do at the beginning of the function:
> 
> 	atomic_long_add(npages, &snp_nr_leaked_pages);
> 

Yes will fix accordingly by incrementing it inside the locked section.

Thanks,
Ashish