[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Qemu-devel] [RFC v3 PATCH 14/14] target-i386: Generate fences for x

From: Richard Henderson
Subject: Re: [Qemu-devel] [RFC v3 PATCH 14/14] target-i386: Generate fences for x86
Date: Tue, 21 Jun 2016 09:23:32 -0700
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.1.1

On 06/21/2016 09:12 AM, Paolo Bonzini wrote:

On 21/06/2016 17:57, Richard Henderson wrote:

                 || (prefixes & PREFIX_LOCK)) {
                 goto illegal_op;
+            tcg_gen_mb(TCG_MO_ST_ST | TCG_BAR_SC);
         case 0xe8 ... 0xef: /* lfence */
+            tcg_gen_mb(TCG_MO_LD_LD | TCG_BAR_SC);
+            break;

These are unnecessary.  On the other hand, _each and every load_ must be
followed by a LD_LD | LD_ST barrier, and each and every store must be
preceded by a LD_ST | ST_ST barrier.

They're not unnecessary if we (1) add those barriers for normal loads
and stores and (2) omit them from the non-temporal loads and stores.

When does TCG generate non-temporal loads and stores?

I was talking about the guest non-temporal loads and stores.


reply via email to

[Prev in Thread] Current Thread [Next in Thread]