Re: [PULL v2 05/13] accel/tcg: Relax va restrictions on 64-bit guests

[Alex Bennée]

Laurent Vivier <laurent@vivier.eu> writes:

> On 15/05/2020 16:43, Alex Bennée wrote:
>> From: Richard Henderson <richard.henderson@linaro.org>
>> 
>> We cannot at present limit a 64-bit guest to a virtual address
>> space smaller than the host.  It will mostly work to ignore this
>> limitation, except if the guest uses high bits of the address
>> space for tags.  But it will certainly work better, as presently
>> we can wind up failing to allocate the guest stack.
>> 
>> Widen our user-only page tree to the host or abi pointer width.
>> Remove the workaround for this problem from target/alpha.
>> Always validate guest addresses vs reserved_va, as there we
>> control allocation ourselves.
>> 
>> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
>> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
>> 
>> Message-Id: <20200513175134.19619-7-alex.bennee@linaro.org>
>> 
>
> This patch breaks a test case in LTP with 64bit targets on x86_64 host:
>
> sudo linux-user/mips64el-linux-user/qemu-mips64el \
> -L chroot/mips64el/stretch/ \
> chroot/mips64el/stretch/opt/ltp/testcases/bin/mmap15
>
> qemu-mips64el: accel/tcg/translate-all.c:2533: page_set_flags: Assertion
> `start < end' failed.
> qemu:handle_cpu_signal received signal outside vCPU context @
> pc=0x7f0015f6e7cb
>
> Could you have a look?

Can confirm I've replicated:

  18:30:20 [alex.bennee@hackbox2:~/l/q/b/user.static] next/various-fixes|✔ 32 +
  sudo ./mips64el-linux-user/qemu-mips64el -L 
~/lsrc/buildroot.git/builds/mips64el/target/ 
~/lsrc/buildroot.git/builds/mips64el/target/usr/lib/ltp-testsuite/testcases/bin/mmap
  15
  [sudo] password for alex.bennee:
  qemu-mips64el: 
/home/alex.bennee/lsrc/qemu.git/accel/tcg/translate-all.c:2533: page_set_flags: 
Assertion `start < end' failed.
  qemu:handle_cpu_signal received signal outside vCPU context @ pc=0x6c28c2

Also TIL you can use buildroot to build ltp ;-)

>
> Thanks,
> Laurent


-- 
Alex Bennée