linux-kernel - Re: [PATCH v8 12/40] x86/sev: Add helper for validating pages in early enc attribute changes

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Message-ID: <7934f88f-8e2b-ea45-6110-202ea8c2ad64@amd.com>
Date:   Tue, 11 Jan 2022 15:22:01 -0600
From:   Brijesh Singh <brijesh.singh@....com>
To:     Venu Busireddy <venu.busireddy@...cle.com>
Cc:     brijesh.singh@....com, x86@...nel.org,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        linux-efi@...r.kernel.org, platform-driver-x86@...r.kernel.org,
        linux-coco@...ts.linux.dev, linux-mm@...ck.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Joerg Roedel <jroedel@...e.de>,
        Tom Lendacky <thomas.lendacky@....com>,
        "H. Peter Anvin" <hpa@...or.com>, Ard Biesheuvel <ardb@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Jim Mattson <jmattson@...gle.com>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Sergio Lopez <slp@...hat.com>, Peter Gonda <pgonda@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        David Rientjes <rientjes@...gle.com>,
        Dov Murik <dovmurik@...ux.ibm.com>,
        Tobin Feldman-Fitzthum <tobin@....com>,
        Borislav Petkov <bp@...en8.de>,
        Michael Roth <michael.roth@....com>,
        Vlastimil Babka <vbabka@...e.cz>,
        "Kirill A . Shutemov" <kirill@...temov.name>,
        Andi Kleen <ak@...ux.intel.com>,
        "Dr . David Alan Gilbert" <dgilbert@...hat.com>,
        tony.luck@...el.com, marcorr@...gle.com,
        sathyanarayanan.kuppuswamy@...ux.intel.com
Subject: Re: [PATCH v8 12/40] x86/sev: Add helper for validating pages in
 early enc attribute changes

Hi Venu,


On 1/3/22 5:28 PM, Venu Busireddy wrote:
...

>> +
>> +	 /*
>> +	  * Ask the hypervisor to mark the memory pages as private in the RMP
>> +	  * table.
>> +	  */
> 
> Indentation is off. While at it, you may want to collapse it into a one
> line comment.
> 

Based on previous review feedback I tried to keep the comment to 80 
character limit.

>> +	early_set_page_state(paddr, npages, SNP_PAGE_STATE_PRIVATE);
>> +
>> +	/* Validate the memory pages after they've been added in the RMP table. */
>> +	pvalidate_pages(vaddr, npages, 1);
>> +}
>> +
>> +void __init early_snp_set_memory_shared(unsigned long vaddr, unsigned long paddr,
>> +					unsigned int npages)
>> +{
>> +	if (!cc_platform_has(CC_ATTR_SEV_SNP))
>> +		return;
>> +
>> +	/*
>> +	 * Invalidate the memory pages before they are marked shared in the
>> +	 * RMP table.
>> +	 */
> 
> Collapse into one line?
> 

same as above.

...

>> +		/*
>> +		 * ON SNP, the page state in the RMP table must happen
>> +		 * before the page table updates.
>> +		 */
>> +		early_snp_set_memory_shared((unsigned long)__va(pa), pa, 1);
> 
> I know "1" implies "true", but to emphasize that the argument is
> actually a boolean, could you please change the "1" to "true?"
> 

I assume you mean the last argument to the 
early_snp_set_memory_{private,shared}. Please note that its a number of 
pages (unsigned int). The 'true' does not make sense to me.

>> +	}
>> +
>>   	/* Change the page encryption mask. */
>>   	new_pte = pfn_pte(pfn, new_prot);
>>   	set_pte_atomic(kpte, new_pte);
>> +
>> +	/*
>> +	 * If page is set encrypted in the page table, then update the RMP table to
>> +	 * add this page as private.
>> +	 */
>> +	if (enc)
>> +		early_snp_set_memory_private((unsigned long)__va(pa), pa, 1);
> 
> Here too, could you please change the "1" to "true?"
> 

same as above.

thanks