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accel/tcg: Avoid reading too much in load_atom_{2,4}

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When load_atom_extract_al16_or_al8 is inexpensive, we want to use
it early, in order to avoid the overhead of required_atomicity.
However, we must not read past the end of the page.

If there are more than 8 bytes remaining, then both the "aligned 16"
and "aligned 8" paths align down so that the read has at least
16 bytes remaining on the page.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
This commit is contained in:
Richard Henderson 2023-08-10 08:37:14 -07:00
parent 64d3be986f
commit 6a2c23ddeb
3 changed files with 47 additions and 3 deletions
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10
accel/tcg/ldst_atomicity.c.inc
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@ -404,7 +404,10 @@ static uint16_t load_atom_2(CPUArchState *env, uintptr_t ra,
return load_atomic2(pv);
}
if (HAVE_ATOMIC128_RO) {
return load_atom_extract_al16_or_al8(pv, 2);
intptr_t left_in_page = -(pi | TARGET_PAGE_MASK);
if (likely(left_in_page > 8)) {
return load_atom_extract_al16_or_al8(pv, 2);
}
}
atmax = required_atomicity(env, pi, memop);
@ -443,7 +446,10 @@ static uint32_t load_atom_4(CPUArchState *env, uintptr_t ra,
return load_atomic4(pv);
}
if (HAVE_ATOMIC128_RO) {
return load_atom_extract_al16_or_al8(pv, 4);
intptr_t left_in_page = -(pi | TARGET_PAGE_MASK);
if (likely(left_in_page > 8)) {
return load_atom_extract_al16_or_al8(pv, 4);
}
}
atmax = required_atomicity(env, pi, memop);