On Fri, Apr 23, 2021 at 3:11 PM Jianxiong Gao <jxgao@xxxxxxxxxx> wrote: > > +Marc, who can help filling the gaps. > -- > Jianxiong Gao Oops. Gao over-trimmed. From lkml, here's Gao's last reply. >> 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. > > I searched online and found what appeared to be a very similar bug > from a few years ago [1]. Ultimately, it was fixed in the device > firmware. However, it began with NVMe + SWIOTLB resulting in similar > issues to what we observed without these patches. > > [1] https://bugzilla.redhat.com/show_bug.cgi?id=1402533 The bug is not specific to SEV virtualization. We've repro'd the bug on vanilla NVMe + SWIOTLB kernels, and confirmed that these patches fix the issue. We simply first encountered it while working on SEV virtualization. The bug itself is that on an NVMe + SWIOTLB setup, `mkfs.xfs -f /dev/nvme2n1` triggers the following error "mkfs.xfs: pwrite failed: Input/output error". We observed this on a RHEL system. An example system where a user might encounter this bug is the following. On a system with NVMe + older 32-bit devices that has been configured with the `swiotlb=force` kernel command line flag to ensure that the 32-bit devices work properly.
