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target/riscv: fix endless translation loop on big endian systems

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On big endian systems, pte and updated_pte hold big endian host data
while pte_pa points to little endian target data. This means the branch
at cpu_helper.c:1669 will be always satisfied and restart translation,
causing an endless translation loop.

The correctness of this patch can be deduced by:

old_pte will hold value either from cpu_to_le32/64(pte) or
cpu_to_le32/64(updated_pte), both of wich is litte endian. After that,
an in-place conversion by le32/64_to_cpu(old_pte) ensures that old_pte
now is in native endian, same with pte. Therefore, the endianness of the
both side of if (old_pte != pte) is correct.

Signed-off-by: Ziqiao Kong <ziqiaokong@gmail.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-ID: <20250415080254.3667878-2-ziqiaokong@gmail.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
Cc: qemu-stable@nongnu.org
This commit is contained in:
Ziqiao Kong 2025-04-15 16:02:54 +08:00 • committed by Alistair Francis
parent 56cde18d04
commit ad63158bdb
1 changed files with 4 additions and 2 deletions
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6
target/riscv/cpu_helper.c
View file

@ -1566,9 +1566,11 @@ static int get_physical_address(CPURISCVState *env, hwaddr *physical,
target_ulong *pte_pa = qemu_map_ram_ptr(mr->ram_block, addr1);
target_ulong old_pte;
if (riscv_cpu_sxl(env) == MXL_RV32) {
old_pte = qatomic_cmpxchg((uint32_t *)pte_pa, pte, updated_pte);
old_pte = qatomic_cmpxchg((uint32_t *)pte_pa, cpu_to_le32(pte), cpu_to_le32(updated_pte));
old_pte = le32_to_cpu(old_pte);
} else {
old_pte = qatomic_cmpxchg(pte_pa, pte, updated_pte);
old_pte = qatomic_cmpxchg(pte_pa, cpu_to_le64(pte), cpu_to_le64(updated_pte));
old_pte = le64_to_cpu(old_pte);
}
if (old_pte != pte) {
goto restart;