On 10.05.22 13:31, Christophe Leroy wrote:
Le 10/05/2022 à 13:18, Alexander Graf a écrit :Commit 863771a28e27 ("powerpc/32s: Convert switch_mmu_context() to C") moved the switch_mmu_context() to C. While in principle a good idea, it meant that the function now uses the stack. The stack is not accessible from real mode though. So to keep calling the function, let's turn on MSR_DR while we call it. That way, all pointer references to the stack are handled virtually.Is the system ready to handle a DSI in case the stack is not mapped ?
A DSI itself will be an interrupt again which will in turn destroy the SPRG that we're saving. Guess I was trying to be too smart :). I'll use Matt's original suggestion and just put it on the stack.
In addition, make sure to save/restore r12 in an SPRG, as it may get clobbered by the C function. Reported-by: Matt Evans <matt@xxxxxxxxxx> Fixes: 863771a28e27 ("powerpc/32s: Convert switch_mmu_context() to C")Oops, sorry for that. I didn't realise that there was other callers to switch_mmu_context() than switch_mm_irqs_off().
No worries, the compiled C version looks a lot nicer than the previous asm one - and it was a good way to identify whether there still are users of KVM on Book3S 32bit out there :)
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