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arm/ptw: Handle atomic updates of page tables entries in MMIO during PTW.

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I'm far from confident this handling here is correct. Hence
RFC.  In particular not sure on what locks I should hold for this
to be even moderately safe.

The function already appears to be inconsistent in what it returns
as the CONFIG_ATOMIC64 block returns the endian converted 'eventual'
value of the cmpxchg whereas the TCG_OVERSIZED_GUEST case returns
the previous value.

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Message-id: 20240219161229.11776-1-Jonathan.Cameron@huawei.com
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
This commit is contained in:
Jonathan Cameron 2024-02-19 16:12:29 +00:00 committed by Peter Maydell
parent 06005459dc
commit 7421ddc4dc
1 changed files with 62 additions and 2 deletions
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64
target/arm/ptw.c
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@ -711,8 +711,68 @@ static uint64_t arm_casq_ptw(CPUARMState *env, uint64_t old_val,
void *host = ptw->out_host;
if (unlikely(!host)) {
fi->type = ARMFault_UnsuppAtomicUpdate;
return 0;
/* Page table in MMIO Memory Region */
CPUState *cs = env_cpu(env);
MemTxAttrs attrs = {
.space = ptw->out_space,
.secure = arm_space_is_secure(ptw->out_space),
};
AddressSpace *as = arm_addressspace(cs, attrs);
MemTxResult result = MEMTX_OK;
bool need_lock = !bql_locked();
if (need_lock) {
bql_lock();
}
if (ptw->out_be) {
cur_val = address_space_ldq_be(as, ptw->out_phys, attrs, &result);
if (unlikely(result != MEMTX_OK)) {
fi->type = ARMFault_SyncExternalOnWalk;
fi->ea = arm_extabort_type(result);
if (need_lock) {
bql_unlock();
}
return old_val;
}
if (cur_val == old_val) {
address_space_stq_be(as, ptw->out_phys, new_val, attrs, &result);
if (unlikely(result != MEMTX_OK)) {
fi->type = ARMFault_SyncExternalOnWalk;
fi->ea = arm_extabort_type(result);
if (need_lock) {
bql_unlock();
}
return old_val;
}
cur_val = new_val;
}
} else {
cur_val = address_space_ldq_le(as, ptw->out_phys, attrs, &result);
if (unlikely(result != MEMTX_OK)) {
fi->type = ARMFault_SyncExternalOnWalk;
fi->ea = arm_extabort_type(result);
if (need_lock) {
bql_unlock();
}
return old_val;
}
if (cur_val == old_val) {
address_space_stq_le(as, ptw->out_phys, new_val, attrs, &result);
if (unlikely(result != MEMTX_OK)) {
fi->type = ARMFault_SyncExternalOnWalk;
fi->ea = arm_extabort_type(result);
if (need_lock) {
bql_unlock();
}
return old_val;
}
cur_val = new_val;
}
}
if (need_lock) {
bql_unlock();
}
return cur_val;
}
/*