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accel/tcg: Set can_do_io at at start of lookup_tb_ptr helper 

If a page table is in IO memory and lookup_tb_ptr probes
the TLB it can result in a page table walk for the instruction
fetch.  If this hits IO memory and io_prepare falsely assumes
it needs to do a TLB recompile.

Avoid that by setting can_do_io at the start of lookup_tb_ptr.

Link: https://lore.kernel.org/qemu-devel/CAFEAcA_a_AyQ=Epz3_+CheAT8Crsk9mOu894wbNW_FywamkZiw@mail.gmail.com/#t

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Message-Id: <20240219173153.12114-2-Jonathan.Cameron@huawei.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
This commit is contained in:
Peter Maydell 2024-02-19 17:31:51 +00:00 committed by Richard Henderson
parent 7f89fdf8eb
commit 62bcba836c
1 changed files with 8 additions and 0 deletions
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8
accel/tcg/cpu-exec.c
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@ -396,6 +396,14 @@ const void *HELPER(lookup_tb_ptr)(CPUArchState *env)
uint64_t cs_base;
uint32_t flags, cflags;
/*
* By definition we've just finished a TB, so I/O is OK.
* Avoid the possibility of calling cpu_io_recompile() if
* a page table walk triggered by tb_lookup() calling
* probe_access_internal() happens to touch an MMIO device.
* The next TB, if we chain to it, will clear the flag again.
*/
cpu->neg.can_do_io = true;
cpu_get_tb_cpu_state(env, &pc, &cs_base, &flags);
cflags = curr_cflags(cpu);