Messages in this thread | | | Date | Wed, 24 Jun 2020 10:07:16 +0800 | From | Baolin Wang <> | Subject | Re: [PATCH 2/3] nvme-pci: Add controller memory buffer supported macro |
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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
Ah, right, I think I should add another version condition: if ((ctrl->vs >= NVME_VS(1, 4, 0) && !NVME_CAP_CMBS(dev->ctrl.cap)) || dev->cmb_size) return;
> 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).
Thanks for your explanation. I saw we've added an CMB sysfs attribute to get the CMB location and size if we enabled CMB, so should we still add some information in nvme_map_cmb() let user know explicitly?
dev_info(dev->ctrl.device, "Registered the CMB, bar=0x%x, size=%lld\n", bar, size);
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