From: Amit Pundir <amit.pundir@linaro.org>
To: Christoph Hellwig <hch@lst.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
jeremy.linton@arm.com, iommu@lists.linux-foundation.org,
linux-rpi-kernel@lists.infradead.org,
David Rientjes <rientjes@google.com>,
Robin Murphy <robin.murphy@arm.com>
Subject: Re: revert scope for 5.8, was Re: dma-pool fixes
Date: Sat, 1 Aug 2020 17:27:04 +0530 [thread overview]
Message-ID: <CAMi1Hd2tCfbDUuBP=OKoG8fPVCTpiARmqrkPadEJjJ52fgc_-Q@mail.gmail.com> (raw)
In-Reply-To: <20200801085706.GA2991@lst.de>
On Sat, 1 Aug 2020 at 14:27, Christoph Hellwig <hch@lst.de> wrote:
>
> On Sat, Aug 01, 2020 at 01:20:07AM -0700, David Rientjes wrote:
> > To follow-up on this, the introduction of the DMA atomic pools in 5.8
> > fixes an issue for any AMD SEV enabled guest that has a driver that
> > requires atomic DMA allocations (for us, nvme) because runtime decryption
> > of memory allocated through the DMA API may block. This manifests itself
> > as "sleeping in invalid context" BUGs for any confidential VM user in
> > cloud.
> >
> > I unfortunately don't have Amit's device to be able to independently debug
> > this issue and certainly could not have done a better job at working the
> > bug than Nicolas and Christoph have done so far. I'm as baffled by the
> > results as anybody else.
> >
> > I fully understand the no regressions policy. I'd also ask that we
> > consider that *all* SEV guests are currently broken if they use nvme or
> > any other driver that does atomic DMA allocations. It's an extremely
> > serious issue for cloud. If there is *anything* that I can do to make
> > forward progress on this issue for 5.8, including some of the workarounds
> > above that Amit requested, I'd be very happy to help. Christoph will make
> > the right decision for DMA in 5.8, but I simply wanted to state how
> > critical working SEV guests are to users.
>
> I'm between a rock and a hard place here. If we simply want to revert
> commits as-is to make sure both the Raspberry Pi 4 and thone phone do
> not regress we'll have to go all the way back and revert the whole SEV
> pool support. I could try to manual revert of the multiple pool
> support, but it is very late for that.
Hi, I found the problematic memory region. It was a memory
chunk reserved/removed in the downstream tree but was
seemingly reserved upstream for different drivers. I failed to
calculate the length of the total region reserved downstream
correctly. And there was still a portion of memory left unmarked,
which I should have marked as reserved in my testing earlier
today.
Sorry for all the noise and thanks Nicolas, Christoph and David
for your patience.
Regards,
Amit Pundir
>
> Or maybe Linus has decided to cut a -rc8 which would give us a little
> more time.
> -
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next prev parent reply other threads:[~2020-08-01 11:57 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-28 10:47 dma-pool fixes Christoph Hellwig
2020-07-28 10:47 ` [PATCH 1/2] dma-pool: fix coherent pool allocations for IOMMU mappings Christoph Hellwig
2020-07-28 14:56 ` Nicolas Saenz Julienne
2020-07-28 15:28 ` Christoph Hellwig
2020-07-28 10:47 ` [PATCH 2/2] dma-pool: Only allocate from CMA when in same memory zone Christoph Hellwig
2020-07-28 12:02 ` dma-pool fixes Amit Pundir
2020-07-28 12:07 ` Christoph Hellwig
2020-07-28 12:25 ` Amit Pundir
2020-07-28 12:41 ` Christoph Hellwig
2020-07-28 12:48 ` Amit Pundir
2020-07-28 15:30 ` Christoph Hellwig
2020-07-29 10:45 ` Nicolas Saenz Julienne
2020-07-29 12:22 ` Amit Pundir
2020-07-31 7:46 ` Amit Pundir
2020-07-31 13:09 ` Christoph Hellwig
2020-07-31 14:15 ` Amit Pundir
2020-07-31 19:04 ` David Rientjes via iommu
2020-08-01 8:20 ` David Rientjes via iommu
2020-08-01 8:57 ` revert scope for 5.8, was " Christoph Hellwig
2020-08-01 11:57 ` Amit Pundir [this message]
2020-08-01 16:59 ` Nicolas Saenz Julienne
2020-08-01 17:39 ` Christoph Hellwig
2020-08-02 4:46 ` Amit Pundir
2020-08-02 15:04 ` Amit Pundir
2020-08-03 4:14 ` David Rientjes via iommu
2020-08-03 6:44 ` Christoph Hellwig
2020-08-03 18:30 ` David Rientjes via iommu
2020-08-01 18:28 ` Linus Torvalds
2020-08-02 4:35 ` Amit Pundir
2020-08-01 8:29 ` Christoph Hellwig
2020-07-31 10:47 ` Nicolas Saenz Julienne
2020-07-31 11:17 ` Amit Pundir
2020-07-31 14:15 ` Nicolas Saenz Julienne
2020-07-31 14:20 ` Amit Pundir
2020-08-01 7:34 ` Amit Pundir
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