linux-kernel - Re: [PATCH v7 14/45] x86/compressed: Add helper for validating pages in the decompression stage

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Date:   Tue, 7 Dec 2021 13:21:05 -0600
From:   Brijesh Singh <brijesh.singh@....com>
To:     Borislav Petkov <bp@...en8.de>
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>,
        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 v7 14/45] x86/compressed: Add helper for validating pages
 in the decompression stage



On 12/7/21 5:48 AM, Borislav Petkov wrote:
> On Wed, Nov 10, 2021 at 04:07:00PM -0600, Brijesh Singh wrote:
>> diff --git a/arch/x86/boot/compressed/ident_map_64.c b/arch/x86/boot/compressed/ident_map_64.c
>> index f7213d0943b8..3cf7a7575f5c 100644
>> --- a/arch/x86/boot/compressed/ident_map_64.c
>> +++ b/arch/x86/boot/compressed/ident_map_64.c
>> @@ -275,15 +275,31 @@ static int set_clr_page_flags(struct x86_mapping_info *info,
>>   	 * Changing encryption attributes of a page requires to flush it from
>>   	 * the caches.
>>   	 */
>> -	if ((set | clr) & _PAGE_ENC)
>> +	if ((set | clr) & _PAGE_ENC) {
>>   		clflush_page(address);
>>   
>> +		/*
>> +		 * If the encryption attribute is being cleared, then change
>> +		 * the page state to shared in the RMP table.
>> +		 */
>> +		if (clr)
>> +			snp_set_page_shared(pte_pfn(*ptep) << PAGE_SHIFT);
> 
> So I'm wondering: __page_state_change() wants a physical address and
> you're reading it out from the PTE here.
> 
> Why not do
> 
> 	__pa(address & PAGE_MASK);
> 
> like it is usually done?

I am okay to use __pa().

thanks