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d="scan'208";a="14585883" To: Jan Beulich References: <78b62646-6fd4-e5b3-bc09-783bb017eaaa@suse.com> <9af3c1bb-5b8f-4ff5-c9ce-2f34af652814@citrix.com> <6fe56e73-6d6c-9f8a-136d-ace39e9c8b09@suse.com> From: Andrew Cooper Message-ID: <0eba5bb2-90f4-12ab-be51-71d22bd04cd7@citrix.com> Date: Wed, 25 Mar 2020 12:25:27 +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: <6fe56e73-6d6c-9f8a-136d-ace39e9c8b09@suse.com> Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit Content-Language: en-GB X-ClientProxiedBy: AMSPEX02CAS01.citrite.net (10.69.22.112) To AMSPEX02CL02.citrite.net (10.69.22.126) Subject: Re: [Xen-devel] [PATCH 7/7] x86emul: support SYSRET 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: "xen-devel@lists.xenproject.org" , Wei Liu , =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" On 25/03/2020 11:55, Jan Beulich wrote: > On 25.03.2020 11:00, Andrew Cooper wrote: >> On 24/03/2020 16:29, Jan Beulich wrote: >>> --- a/xen/arch/x86/x86_emulate/x86_emulate.c >>> +++ b/xen/arch/x86/x86_emulate/x86_emulate.c >>> @@ -5975,6 +5975,60 @@ x86_emulate( >>> goto done; >>> break; >>> >>> + case X86EMUL_OPC(0x0f, 0x07): /* sysret */ >>> + vcpu_must_have(syscall); >>> + /* Inject #UD if syscall/sysret are disabled. */ >>> + fail_if(!ops->read_msr); >>> + if ( (rc = ops->read_msr(MSR_EFER, &msr_val, ctxt)) != X86EMUL_OKAY ) >>> + goto done; >>> + generate_exception_if((msr_val & EFER_SCE) == 0, EXC_UD); >> (as with the SYSCALL side), no need for the vcpu_must_have(syscall) as >> well as this check. > Upon re-reading I'm now confused - are you suggesting to also drop > the EFER.SCE check? No.  The SCE check is critical and needs to remain. The exact delta I had put together was: diff --git a/xen/arch/x86/x86_emulate/x86_emulate.c b/xen/arch/x86/x86_emulate/x86_emulate.c index c730511ebe..57ce7e00be 100644 --- a/xen/arch/x86/x86_emulate/x86_emulate.c +++ b/xen/arch/x86/x86_emulate/x86_emulate.c @@ -5883,9 +5883,11 @@ x86_emulate(    #ifdef __XEN__      case X86EMUL_OPC(0x0f, 0x05): /* syscall */ -        generate_exception_if(!in_protmode(ctxt, ops), EXC_UD); +        if ( !in_protmode(ctxt, ops) || +             ((ctxt->cpuid->x86_vendor & X86_VENDOR_INTEL) && !mode_64bit()) ) +            generate_exception(EXC_UD);   -        /* Inject #UD if syscall/sysret are disabled. */ +        /* Inject #UD if SCE is disabled.  Subsumes the SYSCALL CPUID check. */          fail_if(ops->read_msr == NULL);          if ( (rc = ops->read_msr(MSR_EFER, &msr_val, ctxt)) != X86EMUL_OKAY )              goto done; (Looking at the commit date, Mon Dec 19 13:32:11 2016 is quite a long time ago...) ~Andrew