Re: [PATCH v2 3/3] softmmu: Introduce cpu_address_space_sync

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

On 15/9/23 18:32, Richard Henderson wrote:
> Synchronously check and update the address space for the
> current cpu for any slow path access.
> 
> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1866
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>   include/exec/memory.h |  6 ++++++
>   accel/tcg/cputlb.c    |  2 ++
>   softmmu/physmem.c     | 20 ++++++++++++++++++++
>   3 files changed, 28 insertions(+)
> 
> diff --git a/include/exec/memory.h b/include/exec/memory.h
> index 68284428f8..7ec842076f 100644
> --- a/include/exec/memory.h
> +++ b/include/exec/memory.h
> @@ -2780,6 +2780,12 @@ void address_space_cache_destroy(MemoryRegionCache *cache);
>   IOMMUTLBEntry address_space_get_iotlb_entry(AddressSpace *as, hwaddr addr,
>                                               bool is_write, MemTxAttrs attrs);
>   
> +/*
> + * Ensure all cpu address spaces are up-to-date.
> + * Return true if changes made and tlb flushed.

No return value, stale comment?

> + */
> +void cpu_address_space_sync(CPUState *cpu);
> +
>   /* address_space_translate: translate an address range into an address space
>    * into a MemoryRegion and an address range into that section.  Should be
>    * called from an RCU critical section, to avoid that the last reference
> diff --git a/accel/tcg/cputlb.c b/accel/tcg/cputlb.c
> index 3270f65c20..91be3f3064 100644
> --- a/accel/tcg/cputlb.c
> +++ b/accel/tcg/cputlb.c
> @@ -1827,6 +1827,8 @@ static bool mmu_lookup(CPUArchState *env, vaddr addr, MemOpIdx oi,
>       l->page[1].size = 0;
>       crosspage = (addr ^ l->page[1].addr) & TARGET_PAGE_MASK;
>   
> +    cpu_address_space_sync(env_cpu(env));
> +
>       if (likely(!crosspage)) {
>           mmu_lookup1(env, &l->page[0], l->mmu_idx, type, ra);
>   
> diff --git a/softmmu/physmem.c b/softmmu/physmem.c
> index e1c535380a..5a89caa257 100644
> --- a/softmmu/physmem.c
> +++ b/softmmu/physmem.c
> @@ -2536,6 +2536,26 @@ static void tcg_commit(MemoryListener *listener)
>       }
>   }
>   
> +void cpu_address_space_sync(CPUState *cpu)
> +{
> +    int i, n = cpu->num_ases;
> +    bool need_flush = false;
> +
> +    for (i = 0; i < n; ++i) {
> +        CPUAddressSpace *cpuas = &cpu->cpu_ases[i];
> +        uint32_t gen = qatomic_load_acquire(&cpuas->layout_gen);
> +
> +        if (cpuas->commit_gen != gen) {
> +            cpuas->commit_gen = gen;
> +            cpuas->memory_dispatch = address_space_to_dispatch(cpuas->as);
> +            need_flush = true;
> +        }
> +    }
> +    if (need_flush) {
> +        tlb_flush(cpu);
> +    }
> +}
> +
>   static void memory_map_init(void)
>   {
>       system_memory = g_malloc(sizeof(*system_memory));