On 17.06.2024 16:03, Marek Marczykowski-Górecki wrote: > On Mon, Jun 17, 2024 at 01:22:37PM +0200, Jan Beulich wrote: >> Hello, >> >> while it feels like we had a similar situation before, I can't seem to be >> able to find traces thereof, or associated (Linux) commits. > > Is it some AMD Threadripper system by a chance?
It's an AMD system in any event, yes. I don't have all the details on it. > Previous thread on this issue: > https://lore.kernel.org/xen-devel/CAOCpoWdOH=xgxiqsc1c5ueb1thxajh4wizbczq-qt+d_kak...@mail.gmail.com/ Ah yes, that's probably the one I was vaguely remembering. There it was the kernel image E820 conflicted with. Yet ... >> With >> >> (XEN) Dom0 kernel: 64-bit, PAE, lsb, paddr 0x1000000 -> 0x4000000 >> ... >> (XEN) Dom0 alloc.: 0000000440000000->0000000448000000 (619175 pages to be >> allocated) >> ... >> (XEN) Loaded kernel: ffffffff81000000->ffffffff84000000 >> >> the kernel occupies the space from 16Mb to 64Mb in the initial allocation. >> Page tables come (almost) directly above: >> >> (XEN) Page tables: ffffffff84001000->ffffffff84026000 >> >> I.e. they're just above the 64Mb boundary. Yet sadly in the host E820 map >> there is >> >> (XEN) [0000000004000000, 0000000004009fff] (ACPI NVS) >> >> i.e. a non-RAM range starting at 64Mb. The kernel (currently) won't tolerate >> such an overlap (also if it was overlapping the kernel image, e.g. if on the >> machine in question s sufficiently much larger kernel was used). Yet with its >> fundamental goal of making its E820 match the host one I'm also in trouble >> thinking of possible solutions / workarounds. I certainly do not see Xen >> trying to cover for this, as the E820 map re-arrangement is purely a kernel >> side decision (forward ported kernels got away without, and what e.g. the >> BSDs do is entirely unknown to me). > > In Qubes we have worked around the issue by moving the kernel lower > (CONFIG_PHYSICAL_START=0x200000): > https://github.com/QubesOS/qubes-linux-kernel/commit/3e8be4ac1682370977d4d0dc1d782c428d860282 > > Far from ideal, but gets it bootable... ... as you say, it's a workaround for particular systems, but not generally dealing with the underlying issue. This explains why I couldn't find any patch(es), though. Jan
