linux-kernel - Re: [PATCH 1/2] dma-direct: set_memory_{en,de}crypted() take number of pages

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Date:   Tue, 22 Jan 2019 20:38:46 -0200
From:   Thiago Jung Bauermann <bauerman@...ux.ibm.com>
To:     "Lendacky\, Thomas" <Thomas.Lendacky@....com>
Cc:     "x86\@kernel.org" <x86@...nel.org>,
        "kvm\@vger.kernel.org" <kvm@...r.kernel.org>,
        "iommu\@lists.linux-foundation.org" 
        <iommu@...ts.linux-foundation.org>,
        "linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>,
        Christoph Hellwig <hch@....de>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Robin Murphy <robin.murphy@....com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, Ram Pai <linuxram@...ibm.com>
Subject: Re: [PATCH 1/2] dma-direct: set_memory_{en,de}crypted() take number of pages


Lendacky, Thomas <Thomas.Lendacky@....com> writes:

> On 1/22/19 3:17 PM, Thiago Jung Bauermann wrote:
>> diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
>> index 355d16acee6d..bc78c37220ba 100644
>> --- a/kernel/dma/direct.c
>> +++ b/kernel/dma/direct.c
>> @@ -166,7 +166,7 @@ void *dma_direct_alloc_pages(struct device *dev, size_t size,
>>  
>>  	ret = page_address(page);
>>  	if (force_dma_unencrypted()) {
>> -		set_memory_decrypted((unsigned long)ret, 1 << get_order(size));
>> +		set_memory_decrypted((unsigned long)ret, 1);
>
> The get_order() function will return the order for the specified size. To
> then get the number of pages you perform the shift as is being done. The
> change is definitely wrong since you are now hardcoding the page count to
> 1. The call to __dma_direct_alloc_pages() will allocate more than one page
> if the size is greater than a page.

<facepalm>

You are correct, of course. Sorry for the noise and thanks for explaining.

-- 
Thiago Jung Bauermann
IBM Linux Technology Center