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From: "Thomas Hellström (VMware)" <thomas_os@shipmail.org>
To: Dave Hansen <dave.hansen@intel.com>,
	dri-devel@lists.freedesktop.org, pv-drivers@vmware.com,
	linux-graphics-maintainer@vmware.com,
	linux-kernel@vger.kernel.org
Cc: "Thomas Hellstrom" <thellstrom@vmware.com>,
	"Dave Hansen" <dave.hansen@linux.intel.com>,
	"Andy Lutomirski" <luto@kernel.org>,
	"Peter Zijlstra" <peterz@infradead.org>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"Ingo Molnar" <mingo@redhat.com>,
	"Borislav Petkov" <bp@alien8.de>,
	"H. Peter Anvin" <hpa@zytor.com>,
	"Heiko Carstens" <heiko.carstens@de.ibm.com>,
	"Christian Borntraeger" <borntraeger@de.ibm.com>,
	"Tom Lendacky" <thomas.lendacky@amd.com>,
	"Christian König" <christian.koenig@amd.com>
Subject: Re: [PATCH v2 1/4] x86/mm: Export force_dma_unencrypted
Date: Tue, 3 Sep 2019 20:50:20 +0200	[thread overview]
Message-ID: <1bec048b-8633-4f65-0657-41f65271bcce@shipmail.org> (raw)
In-Reply-To: <10077630-7081-1e57-adc1-222a8d8044a9@intel.com>

On 9/3/19 5:14 PM, Dave Hansen wrote:
> On 9/3/19 6:15 AM, Thomas Hellström (VMware) wrote:
>> The force_dma_unencrypted symbol is needed by TTM to set up the correct
>> page protection when memory encryption is active. Export it.
> It would be great if this had enough background that I didn't have to
> look at patch 4 to figure out what TTM might be.
>
> Why is TTM special?  How many other drivers would have to be modified in
> a one-off fashion if we go this way?  What's the logic behind this being
> a non-GPL export?

TTM tries to abstract mapping of graphics buffer objects regardless 
where they live. Be it in pci memory or system memory. As such it needs 
to figure out the proper page protection. For example if a buffer object 
is moved from pci memory to system memory transparently to a user-space 
application, all user-space mappings need to be killed and then 
reinstated pointing to the new location, sometimes with a new page 
protection.

I try to keep away as much as possible from the non-GPL vs GPL export 
discussions. I have no strong opinion on the subject. Although since 
sev_active() is a non-GPL export, I decided to mimic that.

Thanks
Thomas




WARNING: multiple messages have this Message-ID (diff)
From: "Thomas Hellström (VMware)" <thomas_os@shipmail.org>
To: Dave Hansen <dave.hansen@intel.com>,
	dri-devel@lists.freedesktop.org, pv-drivers@vmware.com,
	linux-graphics-maintainer@vmware.com,
	linux-kernel@vger.kernel.org
Cc: "Tom Lendacky" <thomas.lendacky@amd.com>,
	"Thomas Hellstrom" <thellstrom@vmware.com>,
	"Peter Zijlstra" <peterz@infradead.org>,
	"Dave Hansen" <dave.hansen@linux.intel.com>,
	"Heiko Carstens" <heiko.carstens@de.ibm.com>,
	"Christian Borntraeger" <borntraeger@de.ibm.com>,
	"Ingo Molnar" <mingo@redhat.com>,
	"Borislav Petkov" <bp@alien8.de>,
	"Andy Lutomirski" <luto@kernel.org>,
	"H. Peter Anvin" <hpa@zytor.com>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"Christian König" <christian.koenig@amd.com>
Subject: Re: [PATCH v2 1/4] x86/mm: Export force_dma_unencrypted
Date: Tue, 3 Sep 2019 20:50:20 +0200	[thread overview]
Message-ID: <1bec048b-8633-4f65-0657-41f65271bcce@shipmail.org> (raw)
In-Reply-To: <10077630-7081-1e57-adc1-222a8d8044a9@intel.com>

On 9/3/19 5:14 PM, Dave Hansen wrote:
> On 9/3/19 6:15 AM, Thomas Hellström (VMware) wrote:
>> The force_dma_unencrypted symbol is needed by TTM to set up the correct
>> page protection when memory encryption is active. Export it.
> It would be great if this had enough background that I didn't have to
> look at patch 4 to figure out what TTM might be.
>
> Why is TTM special?  How many other drivers would have to be modified in
> a one-off fashion if we go this way?  What's the logic behind this being
> a non-GPL export?

TTM tries to abstract mapping of graphics buffer objects regardless 
where they live. Be it in pci memory or system memory. As such it needs 
to figure out the proper page protection. For example if a buffer object 
is moved from pci memory to system memory transparently to a user-space 
application, all user-space mappings need to be killed and then 
reinstated pointing to the new location, sometimes with a new page 
protection.

I try to keep away as much as possible from the non-GPL vs GPL export 
discussions. I have no strong opinion on the subject. Although since 
sev_active() is a non-GPL export, I decided to mimic that.

Thanks
Thomas



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  reply	other threads:[~2019-09-03 18:50 UTC|newest]

Thread overview: 53+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-03 13:15 [PATCH v2 0/4] Have TTM support SEV encryption with coherent memory Thomas Hellström (VMware)
2019-09-03 13:15 ` [PATCH v2 1/4] x86/mm: Export force_dma_unencrypted Thomas Hellström (VMware)
2019-09-03 13:46   ` Christoph Hellwig
2019-09-03 14:32     ` Thomas Hellström (VMware)
2019-09-03 16:22       ` Christoph Hellwig
2019-09-03 16:22         ` Christoph Hellwig
2019-09-03 20:46         ` Thomas Hellström (VMware)
2019-09-03 20:46           ` Thomas Hellström (VMware)
2019-09-03 21:41           ` Andy Lutomirski
2019-09-04  6:58           ` Christoph Hellwig
2019-09-04  7:32             ` Thomas Hellström (VMware)
2019-09-04 12:22               ` Christoph Hellwig
2019-09-04 17:28                 ` Thomas Hellström (VMware)
2019-09-03 15:14   ` Dave Hansen
2019-09-03 15:14     ` Dave Hansen
2019-09-03 18:50     ` Thomas Hellström (VMware) [this message]
2019-09-03 18:50       ` Thomas Hellström (VMware)
2019-09-03 13:15 ` [PATCH v2 2/4] s390/mm: " Thomas Hellström (VMware)
2019-09-03 13:46   ` Christoph Hellwig
2019-09-03 13:15 ` [PATCH v2 3/4] drm/ttm, drm/vmwgfx: Correctly support support AMD memory encryption Thomas Hellström (VMware)
2019-09-03 19:38   ` Dave Hansen
2019-09-03 19:51     ` Daniel Vetter
2019-09-03 19:51       ` Daniel Vetter
2019-09-03 19:55       ` Dave Hansen
2019-09-03 20:36         ` Thomas Hellström (VMware)
2019-09-03 20:51           ` Dave Hansen
2019-09-03 21:05             ` Thomas Hellström (VMware)
2019-09-03 21:46               ` Andy Lutomirski
2019-09-03 22:08                 ` Thomas Hellström (VMware)
2019-09-03 22:15                   ` Thomas Hellström (VMware)
2019-09-03 22:15                     ` Thomas Hellström (VMware)
2019-09-03 23:10                     ` Dave Hansen
2019-09-04  8:34                       ` Thomas Hellström (VMware)
2019-09-03 23:15                     ` Andy Lutomirski
2019-09-04  6:49                       ` Thomas Hellström (VMware)
2019-09-04  7:53                         ` Daniel Vetter
2019-09-04 10:37                           ` Thomas Hellström (VMware)
2019-09-04 10:37                             ` Thomas Hellström (VMware)
2019-09-04 11:43                             ` Daniel Vetter
2019-09-04 18:16                         ` Christoph Hellwig
2019-09-04 18:16                           ` Christoph Hellwig
2019-09-04  7:33               ` Koenig, Christian
2019-09-04  8:19                 ` Thomas Hellström (VMware)
2019-09-04  8:42                   ` Thomas Hellström (VMware)
2019-09-04  8:42                     ` Thomas Hellström (VMware)
2019-09-04 11:10                   ` Koenig, Christian
2019-09-04 11:10                     ` Koenig, Christian
2019-09-04 12:35                     ` Thomas Hellström (VMware)
2019-09-04 12:35                       ` Thomas Hellström (VMware)
2019-09-04 13:05                       ` Thomas Hellström (VMware)
2019-09-03 13:15 ` [PATCH v2 4/4] drm/ttm: Cache dma pool decrypted pages when AMD SEV is active Thomas Hellström (VMware)
2019-09-03 15:18 ` [PATCH v2 0/4] Have TTM support SEV encryption with coherent memory Daniel Vetter
2019-09-05 10:43 ` Thomas Hellström (VMware)

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