[Qemu-devel] "accel/tcg: demacro cputlb" break qemu-system-x86_64

[Andrew Randrianasulu]

Hello!

I was compiling latest qemu git, and was surprized to find qemu-system-x86_64
(compiled for 32-bit x86 machine) can't boot any 64-bit kernel anymore.

32-bit kernels and kvm were fine.
So, I run git bisect

./configure --target-list=x86_64-softmmu --disable-werror 

make -j 5

x86_64-softmmu/qemu-system-x86_64 -kernel /boot/bzImage-4.12.0-x64 -accel tcg

git bisect log
git bisect start
# bad: [60905286cb5150de854e08279bca7dfc4b549e91] Merge remote-tracking branch 
'remotes/dgibson/tags/ppc-for-4.1-20190529' into staging
git bisect bad 60905286cb5150de854e08279bca7dfc4b549e91
# good: [32a1a94dd324d33578dca1dc96d7896a0244d768] Update version for v3.1.0 
release
git bisect good 32a1a94dd324d33578dca1dc96d7896a0244d768
# good: [32a1a94dd324d33578dca1dc96d7896a0244d768] Update version for v3.1.0 
release
git bisect good 32a1a94dd324d33578dca1dc96d7896a0244d768
# good: [9403bccfe3e271f04e12c8c64d306e0cff589009] Merge remote-tracking branch 
'remotes/pmaydell/tags/pull-target-arm-20190228-1' into staging
git bisect good 9403bccfe3e271f04e12c8c64d306e0cff589009
# good: [9403bccfe3e271f04e12c8c64d306e0cff589009] Merge remote-tracking branch 
'remotes/pmaydell/tags/pull-target-arm-20190228-1' into staging
git bisect good 9403bccfe3e271f04e12c8c64d306e0cff589009
# good: [a39286dd61e455014694cb6aa44cfa9e5c86d101] nbd: Tolerate some server 
non-compliance in NBD_CMD_BLOCK_STATUS
git bisect good a39286dd61e455014694cb6aa44cfa9e5c86d101
# bad: [bab1671f0fa928fd678a22f934739f06fd5fd035] tcg: Manually expand 
INDEX_op_dup_vec
git bisect bad bab1671f0fa928fd678a22f934739f06fd5fd035
# bad: [bab1671f0fa928fd678a22f934739f06fd5fd035] tcg: Manually expand 
INDEX_op_dup_vec
git bisect bad bab1671f0fa928fd678a22f934739f06fd5fd035
# good: [956fe143b4f254356496a0a1c479fa632376dfec] target/arm: Implement VLLDM 
for v7M CPUs with an FPU
git bisect good 956fe143b4f254356496a0a1c479fa632376dfec
# good: [df06df4f412a67341de0fbb075e74c4dde3c8972] Merge remote-tracking branch 
'remotes/ericb/tags/pull-nbd-2019-05-07' into staging
git bisect good df06df4f412a67341de0fbb075e74c4dde3c8972
# good: [e5a0a6784a63a15d5b1221326fe5c258be6b5561] vvfat: Replace 
bdrv_{read,write}() with bdrv_{pread,pwrite}()
git bisect good e5a0a6784a63a15d5b1221326fe5c258be6b5561
# bad: [01807c8b0e9f5da6981c2e62a3c1d8f661fb178e] Merge remote-tracking branch 
'remotes/armbru/tags/pull-misc-2019-05-13' into staging
git bisect bad 01807c8b0e9f5da6981c2e62a3c1d8f661fb178e
# bad: [04d6556c5c91d6b00c70df7b85e1715a7c7870df] Merge remote-tracking branch 
'remotes/stsquad/tags/pull-demacro-softmmu-100519-1' into staging
git bisect bad 04d6556c5c91d6b00c70df7b85e1715a7c7870df
# good: [c9ba36ff2f56a95dec0ee47f4dab0b22a0a01f86] Merge remote-tracking branch 
'remotes/kevin/tags/for-upstream' into staging
git bisect good c9ba36ff2f56a95dec0ee47f4dab0b22a0a01f86
# bad: [fc1bc777910dc14a3db4e2ad66f3e536effc297d] cputlb: Drop attribute flatten
git bisect bad fc1bc777910dc14a3db4e2ad66f3e536effc297d
# bad: [f1be36969de2fb9b6b64397db1098f115210fcd9] cputlb: Move TLB_RECHECK 
handling into load/store_helper
git bisect bad f1be36969de2fb9b6b64397db1098f115210fcd9
# bad: [eed5664238ea5317689cf32426d9318686b2b75c] accel/tcg: demacro cputlb
git bisect bad eed5664238ea5317689cf32426d9318686b2b75c
# first bad commit: [eed5664238ea5317689cf32426d9318686b2b75c] accel/tcg: 
demacro cputlb

Not sure how many people test qemu-system-x86_64 on 32-bit x86 hosts....

 gcc --version
gcc (GCC) 5.5.0

commit log says

-------------
accel/tcg: demacro cputlb

    Instead of expanding a series of macros to generate the load/store
    helpers we move stuff into common functions and rely on the compiler
    to eliminate the dead code for each variant.
--------------

May be gcc 5.5.0 was not really good in this case ...