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From: Yongji Xie <xieyongji@bytedance.com>
To: John Garry <john.garry@huawei.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>,
	"Jason Wang" <jasowang@redhat.com>,
	"Stefan Hajnoczi" <stefanha@redhat.com>,
	"Stefano Garzarella" <sgarzare@redhat.com>,
	"Parav Pandit" <parav@nvidia.com>,
	"Christoph Hellwig" <hch@infradead.org>,
	"Christian Brauner" <christian.brauner@canonical.com>,
	"Randy Dunlap" <rdunlap@infradead.org>,
	"Matthew Wilcox" <willy@infradead.org>,
	"Al Viro" <viro@zeniv.linux.org.uk>,
	"Jens Axboe" <axboe@kernel.dk>,
	bcrl@kvack.org, "Jonathan Corbet" <corbet@lwn.net>,
	"Mika Penttilä" <mika.penttila@nextfour.com>,
	"Dan Carpenter" <dan.carpenter@oracle.com>,
	joro@8bytes.org, "Greg KH" <gregkh@linuxfoundation.org>,
	"He Zhe" <zhe.he@windriver.com>,
	"Liu Xiaodong" <xiaodong.liu@intel.com>,
	"Joe Perches" <joe@perches.com>,
	"Robin Murphy" <robin.murphy@arm.com>, kvm <kvm@vger.kernel.org>,
	netdev@vger.kernel.org,
	linux-kernel <linux-kernel@vger.kernel.org>,
	virtualization <virtualization@lists.linux-foundation.org>,
	iommu@lists.linux-foundation.org, songmuchun@bytedance.com,
	linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH v11 10/12] vduse: Implement an MMU-based software IOTLB
Date: Fri, 27 Aug 2021 17:25:02 +0800	[thread overview]
Message-ID: <CACycT3uRvB2K7LeVpdv+DkGJGjdORMa2uk5T_PYswtddNOjV4A@mail.gmail.com> (raw)
In-Reply-To: <2d807de3-e245-c2fb-ae5d-7cacbe35dfcb@huawei.com>

On Fri, Aug 27, 2021 at 4:53 PM John Garry <john.garry@huawei.com> wrote:
>
> On 18/08/2021 13:06, Xie Yongji wrote:
> > +
> > +static dma_addr_t
> > +vduse_domain_alloc_iova(struct iova_domain *iovad,
> > +                     unsigned long size, unsigned long limit)
> > +{
> > +     unsigned long shift = iova_shift(iovad);
> > +     unsigned long iova_len = iova_align(iovad, size) >> shift;
> > +     unsigned long iova_pfn;
> > +
> > +     /*
> > +      * Freeing non-power-of-two-sized allocations back into the IOVA caches
> > +      * will come back to bite us badly, so we have to waste a bit of space
> > +      * rounding up anything cacheable to make sure that can't happen. The
> > +      * order of the unadjusted size will still match upon freeing.
> > +      */
> > +     if (iova_len < (1 << (IOVA_RANGE_CACHE_MAX_SIZE - 1)))
> > +             iova_len = roundup_pow_of_two(iova_len);
>
> Whether it's proper to use this "fast" API or not here, this seems to be
> copied verbatim from dma-iommu.c, which tells me that something should
> be factored out.
>

Agreed.

> Indeed, this rounding up seems a requirement of the rcache, so not sure
> why this is not done there.
>

Me too. I guess it is to let users know that space is wasted.

Thanks,
Yongji

  reply	other threads:[~2021-08-27  9:25 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-18 12:06 [PATCH v11 00/12] Introduce VDUSE - vDPA Device in Userspace Xie Yongji
2021-08-18 12:06 ` [PATCH v11 01/12] iova: Export alloc_iova_fast() and free_iova_fast() Xie Yongji
2021-08-23  6:24   ` Jason Wang
2021-08-24 18:08   ` Michael S. Tsirkin
2021-08-25  9:55     ` Will Deacon
2021-08-25 10:39       ` John Garry
2021-08-25 12:17         ` Yongji Xie
2021-08-27  9:03           ` John Garry
2021-08-18 12:06 ` [PATCH v11 02/12] file: Export receive_fd() to modules Xie Yongji
2021-08-18 12:06 ` [PATCH v11 03/12] vdpa: Fix some coding style issues Xie Yongji
2021-08-23  6:27   ` Jason Wang
2021-08-24 11:09   ` Stefano Garzarella
2021-08-18 12:06 ` [PATCH v11 04/12] vdpa: Add reset callback in vdpa_config_ops Xie Yongji
2021-08-23  6:31   ` Jason Wang
2021-08-23  7:44     ` Yongji Xie
2021-08-18 12:06 ` [PATCH v11 05/12] vhost-vdpa: Handle the failure of vdpa_reset() Xie Yongji
2021-08-23  6:32   ` Jason Wang
2021-08-24 11:12   ` Stefano Garzarella
2021-08-18 12:06 ` [PATCH v11 06/12] vhost-iotlb: Add an opaque pointer for vhost IOTLB Xie Yongji
2021-08-18 12:06 ` [PATCH v11 07/12] vdpa: Add an opaque pointer for vdpa_config_ops.dma_map() Xie Yongji
2021-08-18 12:06 ` [PATCH v11 08/12] vdpa: factor out vhost_vdpa_pa_map() and vhost_vdpa_pa_unmap() Xie Yongji
2021-08-18 12:06 ` [PATCH v11 09/12] vdpa: Support transferring virtual addressing during DMA mapping Xie Yongji
2021-08-18 12:06 ` [PATCH v11 10/12] vduse: Implement an MMU-based software IOTLB Xie Yongji
2021-08-27  8:57   ` John Garry
2021-08-27  9:25     ` Yongji Xie [this message]
2021-08-18 12:06 ` [PATCH v11 11/12] vduse: Introduce VDUSE - vDPA Device in Userspace Xie Yongji
2021-08-23  6:56   ` Jason Wang
2021-08-24 18:10   ` Michael S. Tsirkin
2021-08-25  5:37     ` Yongji Xie
2021-08-18 12:06 ` [PATCH v11 12/12] Documentation: Add documentation for VDUSE Xie Yongji
2021-08-23  6:57   ` Jason Wang
2021-08-23  7:54   ` Jason Wang

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