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From: | Richard Henderson |
Subject: | Re: [Qemu-devel] [PATCH v2 10/45] translate-all: guarantee that tb_hash only holds valid TBs |
Date: | Mon, 17 Jul 2017 12:55:03 -1000 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 |
On 07/16/2017 10:03 AM, Emilio G. Cota wrote:
@@ -1073,13 +1073,17 @@ void tb_phys_invalidate(TranslationBlock *tb, tb_page_addr_t page_addr)assert_tb_locked(); - atomic_set(&tb->invalid, true);- /* remove the TB from the hash list */ phys_pc = tb->page_addr[0] + (tb->pc & ~TARGET_PAGE_MASK); h = tb_hash_func(phys_pc, tb->pc, tb->flags, tb->trace_vcpu_dstate); qht_remove(&tcg_ctx.tb_ctx.htable, tb, h);+ /*+ * Mark the TB as invalid *after* it's been removed from tb_hash, which + * eliminates the need to check this bit on lookups. + */ + tb->invalid = true;
I believe you need atomic_store_release here. Previously we were relying on the lock acquisition in qht_remove to provide the required memory barrier.
We definitely need to make sure this reaches memory before we zap the TB in the CPU_FOREACH loop.
r~
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