Incorrect MAS1_TSIZE_SHIFT in ppce500_spin.c causes incorrectly sized TLB.

Bug #1587535 reported by Aaron Larson on 2016-05-31
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This bug affects 1 person
Affects Status Importance Assigned to Milestone
QEMU
Undecided
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Bug Description

When e500 PPC is booted multi-core, the non-boot cores are started via
the spin table. ppce500_spin.c:spin_kick() calls
mmubooke_create_initial_mapping() to allocate a 64MB TLB entry, but
the created TLB entry is only 256KB.

The root cause is that the function computing the size of the TLB
entry, namely booke206_page_size_to_tlb assumes MAS1.TSIZE as defined
by latter PPC cores, specifically n to the power of FOUR * 1KB. The
result is then used by mmubooke_create_initial_mapping using
MAS1_TSIZE_SHIFT, but MAS1_TSIZE_SHIFT is defined assuming TLB entries
are n to the power of TWO * 1KB. I.e., a difference of shift=7 or
shift=8.

Simply changing MAS1_TSIZE_SHIFT from 7 to 8 is not appropriate since
the macro is used elsewhere.

Removing the ">>1" from:

> static inline hwaddr booke206_page_size_to_tlb(uint64_t size)
> {
> return ctz32(size >> 10) >> 1;

and adding an appropriate comment is what I used as a work around:

> static inline hwaddr booke206_page_size_to_tlb(uint64_t size)
> {
> // resulting size is based on MAS1_TSIZE_SHIFT=7 TLB size.
> return ctz32(size >> 10);

Aaron Larson (aaronpublic) wrote :

Patch accepted.

Commit title is:

Eliminate redundant and incorrect function booke206_page_size_to_tlb

Changed in qemu:
status: New → Fix Committed
Thomas Huth (th-huth) wrote :

Patch had been released with QEMU 2.7

Changed in qemu:
status: Fix Committed → Fix Released
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