[Skiboot] [PATCH 1/2] hw/phb3: Fix potential race in EOI

[Stewart Smith]

Michael Neuling <mikey at neuling.org> writes:
> When we EOI we need to clear the present (P) bit in the Interrupt
> Vector Cache (IVC).  We must clear P ensuring that any additional
> interrupts that come in aren't lost while also maintaining coherency
> with the Interrupt Vector Table (IVT).
>
> To do this, the hardware provides a conditional update bit in the
> IVC. This bit ensures that generation counts between the IVT and the
> IVC updates are synchronised.
>
> Unfortunately we never set this the bit to conditionally update the P
> bit in the IVC based on the generation count.  Also, we didn't set
> what we wanted the new generation count to be if the update was
> successful.
>
> This patch fixes sets both of these.  It also reworks and documents
> the code so that mortals may eventually be able to understand this
> process.
>
> Signed-off-by: Michael Neuling <mikey at neuling.org>
> ---
>  hw/phb3.c | 34 +++++++++++++++++++++++++++++-----
>  1 file changed, 29 insertions(+), 5 deletions(-)

Thanks to everybody who solidly tested this patch series.

Now merged to 5.1.x as of c8bea6e01608f77550ef686bb7359094311de810
merged to 5.2.x as of d729ddbfd8cb7b5dc60f336bf7208214c96a3233
and master as of 2fd158b58a8a38a07cde5f0ac354bd127823a0c9

-- 
Stewart Smith
OPAL Architect, IBM.