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[Qemu-devel] [Bug 1587535] [NEW] Incorrect MAS1_TSIZE_SHIFT in ppce500_s
From: |
Aaron Larson |
Subject: |
[Qemu-devel] [Bug 1587535] [NEW] Incorrect MAS1_TSIZE_SHIFT in ppce500_spin.c causes incorrectly sized TLB. |
Date: |
Tue, 31 May 2016 15:32:17 -0000 |
Public bug reported:
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);
** Affects: qemu
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/1587535
Title:
Incorrect MAS1_TSIZE_SHIFT in ppce500_spin.c causes incorrectly sized
TLB.
Status in QEMU:
New
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);
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Aaron Larson <=