From: "Tan, Jianfeng" <jianfeng.tan@intel.com>
To: Jim Murphy <jmurphy@arista.com>, "dev@dpdk.org" <dev@dpdk.org>
Subject: Re: [dpdk-dev] [PATCH v2] net/virtio-user: fix not working on 32-bit system
Date: Wed, 20 Sep 2017 02:17:24 +0000 [thread overview]
Message-ID: <ED26CBA2FAD1BF48A8719AEF02201E36512EB0C4@SHSMSX103.ccr.corp.intel.com> (raw)
In-Reply-To: <CAJC5fi0em1nssBTROzqkG1QCSc20vUybBodKUuspaFOBsxLTyQ@mail.gmail.com>
Hi Jim,
> -----Original Message-----
> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Jim Murphy
> Sent: Wednesday, September 20, 2017 6:24 AM
> To: dev@dpdk.org
> Subject: [dpdk-dev] [PATCH v2] net/virtio-user: fix not working on 32-bit
> system
>
> Hi,
>
> The fix contained in this patch breaks under the following scenario:
>
> 1. A 64 bit host and virtual machine. Therefore all physical addresses are
> 64 bits.
Host, VM and application are 64bit, then I suppose there's no problem?
> 2. A 32 bit user mode DPDK process running on a 64 bit virtual machine (64
> bit kernel).
Ah, this is a case we fail to cover.
>
> In this case, the physical address is 64bits but the virtual address of the
> user process is 32 bits so uintptr_t is only 32 bits. As a result when:
>
> (uintptr_t)(mb) + (vq)->offset)
>
> is referenced, only 32 bits are copied into the descriptor but 64 bits are
> required because in this scenario that is the size of a physical address.
>
> So it seems like we need a way to determine the size of the physical
> address and then VIRTIO_MBUF_ADDR should be written to copy that many
> bytes
> into the uint64_t. Does anyone know how to determine the size of the
> physical address?
It's easy to find a way to decide the length (similar to _offset_), but copying variable length of bytes seems not an efficient way.
Thanks,
Jianfeng
next prev parent reply other threads:[~2017-09-20 2:17 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-19 22:24 Jim Murphy
2017-09-20 2:17 ` Tan, Jianfeng [this message]
2017-09-20 2:55 ` Jim Murphy
-- strict thread matches above, loose matches on Subject: below --
2017-04-13 14:12 [dpdk-dev] [PATCH] " Jianfeng Tan
2017-04-19 2:30 ` [dpdk-dev] [PATCH v2] " Jianfeng Tan
2017-04-19 5:53 ` Yuanhan Liu
2017-04-19 6:21 ` Tan, Jianfeng
2017-04-19 6:24 ` Yuanhan Liu
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