diff options
authorPeter Maydell <peter.maydell@linaro.org>2018-04-13 13:02:36 +0100
committerPeter Maydell <peter.maydell@linaro.org>2018-04-13 13:02:36 +0100
commit27263ed5eff4414adb808d0cb732d2f692b98ee9 (patch)
parent38e83a71d02e026d4a6d0ab1ef9855c4924c2c68 (diff)
tcg/mips: Handle large offsets from target env to tlb_tablemips-fix
The MIPS TCG target makes the assumption that the offset from the target env pointer to the tlb_table is less than about 64K. This used to be true, but gradual addition of features to the Arm target means that it's no longer true there. This results in the build-time assertion failing: In file included from /home/pm215/qemu/include/qemu/osdep.h:36:0, from /home/pm215/qemu/tcg/tcg.c:28: /home/pm215/qemu/tcg/mips/tcg-target.inc.c: In function ‘tcg_out_tlb_load’: /home/pm215/qemu/include/qemu/compiler.h:90:36: error: static assertion failed: "not expecting: offsetof(CPUArchState, tlb_table[NB_MMU_MODES - 1][1]) > 0x7ff0 + 0x7fff" #define QEMU_BUILD_BUG_MSG(x, msg) _Static_assert(!(x), msg) ^ /home/pm215/qemu/include/qemu/compiler.h:98:30: note: in expansion of macro ‘QEMU_BUILD_BUG_MSG’ #define QEMU_BUILD_BUG_ON(x) QEMU_BUILD_BUG_MSG(x, "not expecting: " #x) ^ /home/pm215/qemu/tcg/mips/tcg-target.inc.c:1236:9: note: in expansion of macro ‘QEMU_BUILD_BUG_ON’ QEMU_BUILD_BUG_ON(offsetof(CPUArchState, ^ /home/pm215/qemu/rules.mak:66: recipe for target 'tcg/tcg.o' failed An ideal long term approach would be to rearrange the CPU state so that the tlb_table was not so far along it, but this is tricky because it would move it from the "not cleared on CPU reset" part of the struct to the "cleared on CPU reset" part. As a simple fix for the 2.12 release, make the MIPS TCG target handle an arbitrary offset by emitting more add instructions. This will mean an extra instruction in the fastpath for TCG loads and stores for the affected guests (currently just aarch64-softmmu). Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
1 files changed, 4 insertions, 7 deletions
diff --git a/tcg/mips/tcg-target.inc.c b/tcg/mips/tcg-target.inc.c
index 4b55ab8856..ca5f1d4894 100644
--- a/tcg/mips/tcg-target.inc.c
+++ b/tcg/mips/tcg-target.inc.c
@@ -1229,13 +1229,10 @@ static void tcg_out_tlb_load(TCGContext *s, TCGReg base, TCGReg addrl,
tcg_out_opc_reg(s, ALIAS_PADD, TCG_REG_A0, TCG_REG_A0, TCG_AREG0);
/* Compensate for very large offsets. */
- if (add_off >= 0x8000) {
- /* Most target env are smaller than 32k; none are larger than 64k.
- Simplify the logic here merely to offset by 0x7ff0, giving us a
- range just shy of 64k. Check this assumption. */
- QEMU_BUILD_BUG_ON(offsetof(CPUArchState,
- tlb_table[NB_MMU_MODES - 1][1])
- > 0x7ff0 + 0x7fff);
+ while (add_off >= 0x8000) {
+ /* Most target env are smaller than 32k, but a few are larger than 64k,
+ * so handle an arbitrarily large offset.
+ */
tcg_out_opc_imm(s, ALIAS_PADDI, TCG_REG_A0, TCG_REG_A0, 0x7ff0);
cmp_off -= 0x7ff0;
add_off -= 0x7ff0;