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accel/tcg: keep requested insn count for mmio code fetch #109

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accel/tcg: keep requested insn count for mmio code fetch #109

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17 changes: 11 additions & 6 deletions accel/tcg/translate-all.c
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Original file line number Diff line number Diff line change
Expand Up @@ -303,12 +303,17 @@ TranslationBlock *tb_gen_code(CPUState *cpu,

phys_pc = get_page_addr_code_hostp(env, pc, &host_pc);

if (phys_pc == -1) {
/* XILINX. Allow prefetching more than 1 inst from MMIO */
/* Generate a one-shot TB with 1 insn in it */
cflags = (cflags & ~CF_COUNT_MASK);
}

/*
* XILINX: mainline QEMU generates a one-shot TB with a single
* insn when the code page is not directly addressable
* (phys_pc == -1); this fork instead allows translating more
* than one instruction from MMIO. An explicitly requested
* instruction count (for example an icount budget refill
* asking for exactly N insns) must be preserved in both
* cases: clearing it regenerates an oversized TB that can
* never fit the remaining budget, livelocking the machine
* with the virtual clock frozen.
*/
max_insns = cflags & CF_COUNT_MASK;
if (max_insns == 0) {
max_insns = TCG_MAX_INSNS;
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