linux-kernel - Re: [RFC Part1 PATCH v3 15/17] x86: Add support for changing memory encryption attribute in early boot

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Date:   Mon, 28 Aug 2017 06:49:19 -0500
From:   Brijesh Singh <brijesh.singh@....com>
To:     Borislav Petkov <bp@...e.de>,
        Tom Lendacky <thomas.lendacky@....com>
Cc:     brijesh.singh@....com, linux-kernel@...r.kernel.org,
        x86@...nel.org, linux-efi@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, kvm@...r.kernel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>,
        Andy Lutomirski <luto@...nel.org>,
        Tony Luck <tony.luck@...el.com>,
        Piotr Luc <piotr.luc@...el.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Reza Arbab <arbab@...ux.vnet.ibm.com>,
        David Howells <dhowells@...hat.com>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Laura Abbott <labbott@...hat.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Eric Biederman <ebiederm@...ssion.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Jonathan Corbet <corbet@....net>,
        Dave Airlie <airlied@...hat.com>,
        Kees Cook <keescook@...omium.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Arnd Bergmann <arnd@...db.de>, Tejun Heo <tj@...nel.org>,
        Christoph Lameter <cl@...ux.com>
Subject: Re: [RFC Part1 PATCH v3 15/17] x86: Add support for changing memory
 encryption attribute in early boot

Hi Boris,


On 8/28/17 5:51 AM, Borislav Petkov wrote:

[..]

> +static int __init early_set_memory_enc_dec(resource_size_t paddr,
>> +					   unsigned long size, bool enc)
>> +{
>> +	unsigned long vaddr, vaddr_end, vaddr_next;
>> +	unsigned long psize, pmask;
>> +	int split_page_size_mask;
>> +	pte_t *kpte;
>> +	int level;
>> +
>> +	vaddr = (unsigned long)__va(paddr);
>> +	vaddr_next = vaddr;
>> +	vaddr_end = vaddr + size;
>> +
>> +	/*
>> +	 * We are going to change the physical page attribute from C=1 to C=0
>> +	 * or vice versa. Flush the caches to ensure that data is written into
>> +	 * memory with correct C-bit before we change attribute.
>> +	 */
>> +	clflush_cache_range(__va(paddr), size);
>> +
>> +	for (; vaddr < vaddr_end; vaddr = vaddr_next) {
>> +		kpte = lookup_address(vaddr, &level);
>> +		if (!kpte || pte_none(*kpte))
>> +			return 1;
> Return before flushing TLBs? Perhaps you mean
>
> 			ret = 1;
> 			goto out;
>
> here and out does
>
> 	__flush_tlb_all();
> 	return ret;

thanks, good catch. I will fix in next rev.

-Brijesh