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tcg: Support MMU protection regions smaller than TARGET_PAGE_SIZE

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Add support for MMU protection regions that are smaller than
TARGET_PAGE_SIZE. We do this by marking the TLB entry for those
pages with a flag TLB_RECHECK. This flag causes us to always
take the slow-path for accesses. In the slow path we can then
special case them to always call tlb_fill() again, so we have
the correct information for the exact address being accessed.

This change allows us to handle reading and writing from small
regions; we cannot deal with execution from the small region.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20180620130619.11362-2-peter.maydell@linaro.org
This commit is contained in:
Peter Maydell 2018-06-26 17:50:41 +01:00
parent d29183d3c0
commit 55df6fcf54
3 changed files with 130 additions and 30 deletions
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5
include/exec/cpu-all.h
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@ -330,11 +330,14 @@ CPUArchState *cpu_copy(CPUArchState *env);
#define TLB_NOTDIRTY (1 << (TARGET_PAGE_BITS - 2))
/* Set if TLB entry is an IO callback. */
#define TLB_MMIO (1 << (TARGET_PAGE_BITS - 3))
/* Set if TLB entry must have MMU lookup repeated for every access */
#define TLB_RECHECK (1 << (TARGET_PAGE_BITS - 4))
/* Use this mask to check interception with an alignment mask
* in a TCG backend.
*/
#define TLB_FLAGS_MASK (TLB_INVALID_MASK | TLB_NOTDIRTY | TLB_MMIO)
#define TLB_FLAGS_MASK (TLB_INVALID_MASK | TLB_NOTDIRTY | TLB_MMIO \
| TLB_RECHECK)
void dump_exec_info(FILE *f, fprintf_function cpu_fprintf);
void dump_opcount_info(FILE *f, fprintf_function cpu_fprintf);