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.
