From: Jason Gunthorpe <jgg@nvidia.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: Tom Lendacky <thomas.lendacky@amd.com>, <x86@kernel.org>,
<linux-kernel@vger.kernel.org>, <linux-arch@vger.kernel.org>,
<linux-mm@kvack.org>, <kvm@vger.kernel.org>,
Radim Kr??m???? <rkrcmar@redhat.com>,
Arnd Bergmann <arnd@arndb.de>,
Matt Fleming <matt@codeblueprint.co.uk>,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
Andrey Ryabinin <aryabinin@virtuozzo.com>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Andy Lutomirski <luto@kernel.org>,
"H. Peter Anvin" <hpa@zytor.com>,
Paolo Bonzini <pbonzini@redhat.com>,
"Alexander Potapenko" <glider@google.com>,
Thomas Gleixner <tglx@linutronix.de>,
"Dmitry Vyukov" <dvyukov@google.com>,
Rik van Riel <riel@redhat.com>,
Larry Woodman <lwoodman@redhat.com>,
Dave Young <dyoung@redhat.com>,
Toshimitsu Kani <toshi.kani@hpe.com>,
"Michael S. Tsirkin" <mst@redhat.com>,
Brijesh Singh <brijesh.singh@amd.com>
Subject: Re: AMD SME encrpytion and PCI BAR pages to user space
Date: Tue, 27 Oct 2020 08:58:10 -0300 [thread overview]
Message-ID: <20201027115810.GH1523783@nvidia.com> (raw)
In-Reply-To: <20201027084357.GA10053@infradead.org>
On Tue, Oct 27, 2020 at 08:43:57AM +0000, Christoph Hellwig wrote:
> On Wed, Oct 21, 2020 at 01:03:22PM -0300, Jason Gunthorpe wrote:
> > Oh, interesting.. Yes the issue is no userspace DMA stuff uses the DMA
> > API correctly (because it is in userspace)
> >
> > So SWIOTLB tricks don't work, I wish the dma_map could fail for these
> > situations
>
> Userspace DMA by definition also does not use dma_map..
? Sure it does, ib_dma_map_sg_attrs() is what RDMA uses
What all the userspace users skip is the dma_sync*() - that would
require a kernel call which defeats the point.
So, my desire is some flag to dma_map_sg() that says
'user space mapping no dma_sync_*'
ie dma_sync_* is a NOP
Then things like SWIOTLB on the SEV system can fail with an error code
instead of malfunctioning
If FOLL_LONGERM is some estimate of this pattern then we have these users:
- drivers/infiniband
- v4l
- vdpa
- xdp
- rds
- habana labs
Jason
prev parent reply other threads:[~2020-10-27 11:58 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-19 15:25 Jason Gunthorpe
2020-10-19 16:36 ` Tom Lendacky
2020-10-19 17:00 ` Jason Gunthorpe
2020-10-19 17:11 ` Tom Lendacky
2020-10-19 17:25 ` Jason Gunthorpe
2020-10-21 11:59 ` Jason Gunthorpe
2020-10-21 15:30 ` Tom Lendacky
2020-10-21 16:03 ` Jason Gunthorpe
2020-10-27 8:43 ` Christoph Hellwig
2020-10-27 11:58 ` Jason Gunthorpe [this message]
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