tcg: Always pass the full write size to notdirty_write()

[PATCH RFC 0/1] tcg: Always pass the full write size to notdirty_write()

Ilya Leoshkevich posted 1 patch 9 months, 2 weeks ago

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Maintainers: Richard Henderson <richard.henderson@linaro.org>, Paolo Bonzini <pbonzini@redhat.com>

accel/tcg/cputlb.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

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[PATCH RFC 0/1] tcg: Always pass the full write size to notdirty_write()

Posted by Ilya Leoshkevich 9 months, 2 weeks ago

Hi,

this is the fix for an issue I complained about a few days back on the
IRC. Unfortunately my reproducer [1] does not work anymore, so I'm
sending this separately and as an RFC.

The user-visible effect was that:

- If a TB writes to itself;
- The address of the write is before the TB start;
- The newly written instruction causes an exception;
- Then single-stepping the instruction that does a write gets you to
  an interrupt handler and not to the newly written "bad" instruction.

You can still see that something is wrong with the softmmu reproducer
in the debugger though. In helper_vstl(), probe_write_access() does not
lead to cpu_loop_exit_noexc() - which I think it should, but
cpu_stq_be_data_ra() still does, masking the issue.

Best regards,
Ilya

[1] https://lists.gnu.org/archive/html/qemu-devel/2023-08/msg01081.html

Ilya Leoshkevich (1):
  tcg: Always pass the full write size to notdirty_write()

 accel/tcg/cputlb.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

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2.41.0