From: Christoph Hellwig <hch@lst.de>
To: Yan Zhao <yan.y.zhao@intel.com>
Cc: Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>,
Felipe Balbi <balbi@kernel.org>,
"Michael S. Tsirkin" <mst@redhat.com>,
Jason Wang <jasowang@redhat.com>,
intel-gvt-dev@lists.freedesktop.org,
Felix Kuehling <Felix.Kuehling@amd.com>,
linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org,
amd-gfx@lists.freedesktop.org, io-uring@vger.kernel.org,
linux-mm@kvack.org, Zhenyu Wang <zhenyuw@linux.intel.com>,
intel-gfx@lists.freedesktop.org, linux-fsdevel@vger.kernel.org,
Alex Deucher <alexander.deucher@amd.com>,
Andrew Morton <akpm@linux-foundation.org>,
virtualization@lists.linux-foundation.org,
Linus Torvalds <torvalds@linux-foundation.org>,
Zhi Wang <zhi.a.wang@intel.com>,
Al Viro <viro@zeniv.linux.org.uk>
Subject: Re: [PATCH 2/6] i915/gvt/kvm: a NULL ->mm does not mean a thread is a kthread
Date: Tue, 14 Apr 2020 09:00:13 +0200 [thread overview]
Message-ID: <20200414070013.GA23680@lst.de> (raw)
In-Reply-To: <20200414000410.GE10586@joy-OptiPlex-7040>
On Mon, Apr 13, 2020 at 08:04:10PM -0400, Yan Zhao wrote:
> > I can't think of another way for a kernel thread to have a mm indeed.
> for example, before calling to vfio_dma_rw(), a kernel thread has already
> called use_mm(), then its current->mm is not null, and it has flag
> PF_KTHREAD.
> in this case, we just want to allow the copy_to_user() directly if
> current->mm == mm, rather than call another use_mm() again.
>
> do you think it makes sense?
I mean no other way than using use_mm. That being said nesting
potentional use_mm callers sounds like a rather bad idea, and we
should avoid that.
next prev parent reply other threads:[~2020-04-14 7:00 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-04 9:40 improve use_mm / unuse_mm Christoph Hellwig
2020-04-04 9:40 ` [PATCH 1/6] amdgpu: a NULL ->mm does not mean a thread is a kthread Christoph Hellwig
2020-04-06 16:07 ` Felix Kuehling
2020-04-04 9:40 ` [PATCH 2/6] i915/gvt/kvm: " Christoph Hellwig
2020-04-04 10:05 ` Sergei Shtylyov
2020-04-07 3:08 ` Yan Zhao
2020-04-13 13:27 ` Christoph Hellwig
2020-04-14 0:04 ` Yan Zhao
2020-04-14 7:00 ` Christoph Hellwig [this message]
2020-04-14 7:03 ` Yan Zhao
2020-04-04 9:40 ` [PATCH 3/6] i915/gvt: remove unused xen bits Christoph Hellwig
2020-04-08 1:44 ` Zhenyu Wang
2020-04-13 13:08 ` Christoph Hellwig
2020-04-14 3:04 ` Zhenyu Wang
2020-04-04 9:40 ` [PATCH 4/6] kernel: move use_mm/unuse_mm to kthread.c Christoph Hellwig
2020-04-06 16:09 ` Felix Kuehling
2020-04-04 9:41 ` [PATCH 5/6] kernel: better document the use_mm/unuse_mm API contract Christoph Hellwig
2020-04-04 13:07 ` [Intel-gfx] " Pavel Begunkov
2020-04-06 16:10 ` Felix Kuehling
2020-04-04 9:41 ` [PATCH 6/6] kernel: set USER_DS in kthread_use_mm Christoph Hellwig
2020-04-06 21:49 ` Michael S. Tsirkin
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