On Fri, Apr 23, 2021 at 10:28:32AM -0700, Jianxiong Gao wrote:
How? Anything that installed 5.10 when it was released never had this working, they had to move to 5.12 to get that to work.
I wasn't clear. The bug is not specific to SEV virtualization. We simply encountered it while working on SEV virtualization. This is a pre-existing bug.
Briefly, the NVMe spec expects a page offset to be retained from the memory address space to the IO address space.
Before these patches, the SWIOTLB truncates any page offset.
Thus, all NVMe + SWIOTLB systems are broken due to this bug without these patches.
Ok, and what prevents you from adding this new feature do your "custom" kernel, or to use 5.12 instead?
This is a new feature that Linux has never supported, and these patches are not "trivial" at all. I also do not see the maintainer of the subsystem agreeing that these are needed to be backported, which is not a good sign.
So I recommend just using a newer kernel version, that way all will be good and no need to backport anything. What is preventing you from doing that today?
thanks,
greg k-h