Re: [edk2-devel] [PATCH 2/2] MdeModulePkg/DxeCore: Fix stack overflow issue due to nested interrupts

["Michael Brown" <mcb30@ipxe.org>]

On 29/02/2024 13:02, Ni, Ray wrote:
> A ideal solution is to not keep the interrupt disabled when
> RestoreTPL(TPL_HIGH -> not TPL_HIGH) is executed in the timer interrupt
> context because the interrupt handler will re-enable the interrupt with
> arch specific instructions (e.g.: IRET for x86).
> 
> The patch introduces mInterruptedTplMask which tells RestoreTPL() if
> it's called in the interrupt context and whether it should defer enabling
> the interrupt.

NACK.  This breaks the specification-defined behaviour for RestoreTPL().

What guarantees do we have that there is no code anywhere in the world 
that relies upon RestoreTPL() unconditionally re-enabling interrupts.

I also find this code substantially harder to follow than 
NestedInterruptTplLib (which does not break any specified behaviour).

Thanks,

Michael



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