linux-kernel - Re: [PATCH v6 2/5] x86/mm: fix sme_populate

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Date:   Mon, 10 Sep 2018 07:28:08 -0500
From:   Brijesh Singh <brijesh.singh@....com>
To:     Borislav Petkov <bp@...e.de>
Cc:     brijesh.singh@....com, x86@...nel.org,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        Tom Lendacky <thomas.lendacky@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Radim Krčmář <rkrcmar@...hat.com>
Subject: Re: [PATCH v6 2/5] x86/mm: fix sme_populate_pgd() to update page
 flags



On 9/10/18 6:36 AM, Borislav Petkov wrote:
> On Fri, Sep 07, 2018 at 12:57:27PM -0500, Brijesh Singh wrote:
>> Fix sme_populate_pgd() to update page flags if the PMD/PTE entry
>> already exists.
>>
>> Signed-off-by: Brijesh Singh <brijesh.singh@....com>
>> Reviewed-by: Tom Lendacky <thomas.lendacky@....com>
>> Cc: Tom Lendacky <thomas.lendacky@....com>
>> Cc: kvm@...r.kernel.org
>> Cc: Thomas Gleixner <tglx@...utronix.de>
>> Cc: Borislav Petkov <bp@...e.de>
>> Cc: "H. Peter Anvin" <hpa@...or.com>
>> Cc: linux-kernel@...r.kernel.org
>> Cc: Paolo Bonzini <pbonzini@...hat.com>
>> Cc: Sean Christopherson <sean.j.christopherson@...el.com>
>> Cc: kvm@...r.kernel.org
>> Cc: "Radim Krčmář" <rkrcmar@...hat.com>
>> ---
>>  arch/x86/mm/mem_encrypt_identity.c | 6 +-----
>>  1 file changed, 1 insertion(+), 5 deletions(-)
>>
>> diff --git a/arch/x86/mm/mem_encrypt_identity.c b/arch/x86/mm/mem_encrypt_identity.c
>> index 92265d3..7659e65 100644
>> --- a/arch/x86/mm/mem_encrypt_identity.c
>> +++ b/arch/x86/mm/mem_encrypt_identity.c
>> @@ -154,9 +154,6 @@ static void __init sme_populate_pgd_large(struct sme_populate_pgd_data *ppd)
>>  		return;
>>  
>>  	pmd = pmd_offset(pud, ppd->vaddr);
>> -	if (pmd_large(*pmd))
>> -		return;
>> -
>>  	set_pmd(pmd, __pmd(ppd->paddr | ppd->pmd_flags));
>>  }
>>  
>> @@ -182,8 +179,7 @@ static void __init sme_populate_pgd(struct sme_populate_pgd_data *ppd)
>>  		return;
>>  
>>  	pte = pte_offset_map(pmd, ppd->vaddr);
>> -	if (pte_none(*pte))
>> -		set_pte(pte, __pte(ppd->paddr | ppd->pte_flags));
>> +	set_pte(pte, __pte(ppd->paddr | ppd->pte_flags));
>>  }
>>  
>>  static void __init __sme_map_range_pmd(struct sme_populate_pgd_data *ppd)
>> -- 
> This looks like a bugfix to me and as such should be:
>
> * at the beginning of the series
> * contain a Fixes: tag
> * contain Cc: <stable@...r.kernel.org>
>
> Right?

Based on your advice I  was going to submit this series to stable
separately. This particular issue is not affecting anyone right now. The
only user to this function is sme_kernel_encrypt() which never updates
the PTE/PMD entries.  I can update the commit message like this this to
clarify it.

Enhance the sme_populate_pgd() to update page flags if the PMD/PTE entry
already exists.



> With that addressed:
>
> Reviewed-by: Borislav Petkov <bp@...e.de>
>