On Mon, Jun 10, 2024 at 03:40:20PM +0200, Borislav Petkov wrote:
> On Fri, Jun 07, 2024 at 06:14:28PM +0300, Kirill A. Shutemov wrote:
> > I was able to address this issue by switching cpa_lock to a mutex.
> > However, this solution will only work if the callers for set_memory
> > interfaces are not called from an atomic context. I need to verify if
> > this is the case.
>
> Dunno, I'd be nervous about this. Althouth from looking at
>
> ad5ca55f6bdb ("x86, cpa: srlz cpa(), global flush tlb after splitting big page and before doing cpa")
>
> I don't see how "So that we don't allow any other cpu" can't be done
> with a mutex. Perhaps the set_memory* interfaces should be usable in as
> many contexts as possible.
>
> Have you run this with lockdep enabled?
Yes, it booted to the shell just fine. However, that doesn't prove
anything. The set_memory_* function has many obscured cases.
> > - The function __flush_tlb_all() in kernel_(un)map_pages_in_pgd() must be
> > called with preemption disabled. Once again, I am unsure why this has
> > not caused issues in the EFI case.
>
> It could be because EFI does all that setup on the BSP only before the
> others have arrived but I don't remember anymore... It is more than
> a decade ago when I did this...
Are you okay with this? Disabling preemption looks strange, but I don't
see a better option.
--
Kiryl Shutsemau / Kirill A. Shutemov
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