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d="scan'208";a="14622382" To: Jan Beulich , "xen-devel@lists.xenproject.org" References: <6fa81b4d-528d-5c33-50c5-a18396b4383a@suse.com> <01414205-1157-9d50-8d45-3e833b430c8e@suse.com> From: Andrew Cooper Message-ID: Date: Wed, 25 Mar 2020 20:58:21 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: <01414205-1157-9d50-8d45-3e833b430c8e@suse.com> Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Content-Language: en-GB X-ClientProxiedBy: AMSPEX02CAS02.citrite.net (10.69.22.113) To AMSPEX02CL02.citrite.net (10.69.22.126) Subject: Re: [Xen-devel] [PATCH v5 02/10] x86emul: support MOVDIRI insn X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Cc: Paul Durrant , Wei Liu , Roger Pau Monne Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" On 24/03/2020 12:29, Jan Beulich wrote: > Note that SDM revision 070 doesn't specify exception behavior for > ModRM.mod == 0b11; assuming #UD here. Didn't I confirm this behaviour for you last time around? > @@ -10075,6 +10079,14 @@ x86_emulate( > : "0" ((uint32_t)src.val), "rm" (_regs.edx) ); > break; > > + case X86EMUL_OPC(0x0f38, 0xf9): /* movdiri mem,r */ > + vcpu_must_have(movdiri); > + generate_exception_if(dst.type != OP_MEM, EXC_UD); > + /* Ignore the non-temporal behavior for now. */ > + dst.val = src.val; > + sfence = true; Looking again at the SDM, I'm not entirely sure this is good enough. Even on top of WB/WP mappings, it needs to have WC properties, knock aliasing lines out of the cache, and ending up as a bus transaction. Also, I'm not convinced the current chunking algorithm for qemu which repeatedly subdivides down to 1, is compatible with the misaligned behaviour described, guaranteeing a split of two. ~Andrew