Re: [Qemu-devel] [PATCH v3] RISC-V: Fix riscv_isa_string memory size bug

["Richard W.M. Jones" <rjones@redhat.com>]

On Mon, Mar 19, 2018 at 11:35:51AM -0700, Michael Clark wrote:
> The RISC-V post-merge spec conformance and cleanup series has had a lot of
> testing. I've been using it to compile QEMU inside of QEMU using the RISC-V
> Fedora Image and its native RISC-V GCC toolchain running inside SMP Linux
> 4.16-rc2. It appears to be pretty rock-solid. The rcu lock fix would likely
> only affect users who are ballooning memory while a guest is under load.
> The page walker changes have also been tested under load (including
> performance tests).

Did you see the problem with restoring floating point registers on
context switch?  The test case is quite simple:

  http://oirase.annexia.org/tmp/sched.c

Note you must compile it with gcc -O2 to manifest the bug.  (We
originally thought it was a problem with gcc's optimization, but it
isn't.)

In Fedora's qemu tree are carrying the following patch which is just a
workaround:

  https://github.com/rwmjones/fedora-riscv-bootstrap/blob/master/stage1-riscv-qemu/force-float-save.patch

Rich.

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