lkml.org 
[lkml]   [2020]   [Jun]   [23]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 2/3] nvme-pci: Add controller memory buffer supported macro
On Tue, Jun 23, 2020 at 06:27:51PM +0200, Christoph Hellwig wrote:
> On Tue, Jun 23, 2020 at 09:24:33PM +0800, Baolin Wang wrote:
> > Introduce a new capability macro to indicate if the controller
> > supports the memory buffer or not, instead of reading the
> > NVME_REG_CMBSZ register.
>
> This is a complex issue. The CMBS bit was only added in NVMe 1.4 as
> a backwards incompatible change, as the CMB addressing scheme can lead
> to data corruption. The CMBS was added as part of the horribe hack
> that also involves the CBA field, which we'll need to see before
> using it to work around the addressing issue. At the same time we
> should also continue supporting the legacy pre-1.4 CMB with a warning
> (and may reject it if we know we run in a VM).

Well, a CMB from an emulated controller (like qemu's) can be used within
a VM. It's only if you direct assign a PCI function that CMB usage
breaks.

\
 
 \ /
  Last update: 2020-06-24 04:59    [W:1.258 / U:0.004 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site