alignment may overlap the TLB flags

Hi,
In QEMU-4.2.0, or git-9b26a610936deaf436af9b7e39e4b7f0a35e4409, alignment may overlap the TLB flags. 
For example, the alignment: MO_ALIGN_32,
    MO_ALIGN_32 = 5 << MO_ASHIFT,
and the TLB flag: TLB_DISCARD_WRITE
#define TLB_DISCARD_WRITE   (1 << (TARGET_PAGE_BITS_MIN - 6))

then, in the function "get_alignment_bits", the assert may fail:

#if defined(CONFIG_SOFTMMU)
    /* The requested alignment cannot overlap the TLB flags.  */
    tcg_debug_assert((TLB_FLAGS_MASK & ((1 << a) - 1)) == 0);
#endif

However, the alignment of MO_ALIGN_32 is not used for now, so the assert cannot be triggered in current version. Anyway it seems like a potential conflict.

That is of course completely dependent on the target page size.  So, yes, a target with a very small page size cannot use large alignments.  The assert makes sure.

Is this comment simply by inspection, or did you have an actual bug to report?

This is an inspection yet.
For ARM SMMU simulation, TARGET_PAGE_BITS_MIN is 10. All low bits of the TLB virtual address are used up by TLB flags and alignment flags. It's a little crowded.
/*
 * ARMv7 and later CPUs have 4K pages minimum, but ARMv5 and v6
 * have to support 1K tiny pages.
 */
# define TARGET_PAGE_BITS_VARY
# define TARGET_PAGE_BITS_MIN  10