Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754725AbbKWQ3s (ORCPT ); Mon, 23 Nov 2015 11:29:48 -0500 Received: from terminus.zytor.com ([198.137.202.10]:44762 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753090AbbKWQ3p (ORCPT ); Mon, 23 Nov 2015 11:29:45 -0500 Date: Mon, 23 Nov 2015 08:28:35 -0800 From: tip-bot for Boris Ostrovsky Message-ID: Cc: dvlasenk@redhat.com, linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, hpa@zytor.com, mingo@kernel.org, bp@alien8.de, luto@kernel.org, tglx@linutronix.de, akpm@linux-foundation.org, brgerst@gmail.com, bp@suse.de, boris.ostrovsky@oracle.com, peterz@infradead.org, luto@amacapital.net Reply-To: bp@suse.de, brgerst@gmail.com, boris.ostrovsky@oracle.com, luto@amacapital.net, peterz@infradead.org, akpm@linux-foundation.org, tglx@linutronix.de, hpa@zytor.com, torvalds@linux-foundation.org, mingo@kernel.org, luto@kernel.org, bp@alien8.de, linux-kernel@vger.kernel.org, dvlasenk@redhat.com In-Reply-To: <1447970147-1733-2-git-send-email-boris.ostrovsky@oracle.com> References: <1447970147-1733-2-git-send-email-boris.ostrovsky@oracle.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/asm] x86/xen: Avoid fast syscall path for Xen PV guests Git-Commit-ID: 5fdf5d37f40a3b18c0d613463867f71c017b75ef X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4685 Lines: 126 Commit-ID: 5fdf5d37f40a3b18c0d613463867f71c017b75ef Gitweb: http://git.kernel.org/tip/5fdf5d37f40a3b18c0d613463867f71c017b75ef Author: Boris Ostrovsky AuthorDate: Thu, 19 Nov 2015 16:55:45 -0500 Committer: Ingo Molnar CommitDate: Mon, 23 Nov 2015 10:48:16 +0100 x86/xen: Avoid fast syscall path for Xen PV guests After 32-bit syscall rewrite, and specifically after commit: 5f310f739b4c ("x86/entry/32: Re-implement SYSENTER using the new C path") ... the stack frame that is passed to xen_sysexit is no longer a "standard" one (i.e. it's not pt_regs). Since we end up calling xen_iret from xen_sysexit we don't need to fix up the stack and instead follow entry_SYSENTER_32's IRET path directly to xen_iret. We can do the same thing for compat mode even though stack does not need to be fixed. This will allow us to drop usergs_sysret32 paravirt op (in the subsequent patch) Suggested-by: Andy Lutomirski Signed-off-by: Boris Ostrovsky Reviewed-by: Borislav Petkov Acked-by: Andy Lutomirski Cc: Andrew Morton Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: david.vrabel@citrix.com Cc: konrad.wilk@oracle.com Cc: virtualization@lists.linux-foundation.org Cc: xen-devel@lists.xenproject.org Link: http://lkml.kernel.org/r/1447970147-1733-2-git-send-email-boris.ostrovsky@oracle.com Signed-off-by: Ingo Molnar --- arch/x86/entry/entry_32.S | 5 +++-- arch/x86/entry/entry_64_compat.S | 10 ++++++---- arch/x86/include/asm/cpufeature.h | 1 + arch/x86/xen/enlighten.c | 4 +++- 4 files changed, 13 insertions(+), 7 deletions(-) diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S index 3eb572e..0870825 100644 --- a/arch/x86/entry/entry_32.S +++ b/arch/x86/entry/entry_32.S @@ -308,8 +308,9 @@ sysenter_past_esp: movl %esp, %eax call do_fast_syscall_32 - testl %eax, %eax - jz .Lsyscall_32_done + /* XEN PV guests always use IRET path */ + ALTERNATIVE "testl %eax, %eax; jz .Lsyscall_32_done", \ + "jmp .Lsyscall_32_done", X86_FEATURE_XENPV /* Opportunistic SYSEXIT */ TRACE_IRQS_ON /* User mode traces as IRQs on. */ diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S index c320183..402e34a 100644 --- a/arch/x86/entry/entry_64_compat.S +++ b/arch/x86/entry/entry_64_compat.S @@ -121,8 +121,9 @@ sysenter_flags_fixed: movq %rsp, %rdi call do_fast_syscall_32 - testl %eax, %eax - jz .Lsyscall_32_done + /* XEN PV guests always use IRET path */ + ALTERNATIVE "testl %eax, %eax; jz .Lsyscall_32_done", \ + "jmp .Lsyscall_32_done", X86_FEATURE_XENPV jmp sysret32_from_system_call sysenter_fix_flags: @@ -200,8 +201,9 @@ ENTRY(entry_SYSCALL_compat) movq %rsp, %rdi call do_fast_syscall_32 - testl %eax, %eax - jz .Lsyscall_32_done + /* XEN PV guests always use IRET path */ + ALTERNATIVE "testl %eax, %eax; jz .Lsyscall_32_done", \ + "jmp .Lsyscall_32_done", X86_FEATURE_XENPV /* Opportunistic SYSRET */ sysret32_from_system_call: diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h index e4f8010..f7ba9fb 100644 --- a/arch/x86/include/asm/cpufeature.h +++ b/arch/x86/include/asm/cpufeature.h @@ -216,6 +216,7 @@ #define X86_FEATURE_PAUSEFILTER ( 8*32+13) /* AMD filtered pause intercept */ #define X86_FEATURE_PFTHRESHOLD ( 8*32+14) /* AMD pause filter threshold */ #define X86_FEATURE_VMMCALL ( 8*32+15) /* Prefer vmmcall to vmcall */ +#define X86_FEATURE_XENPV ( 8*32+16) /* "" Xen paravirtual guest */ /* Intel-defined CPU features, CPUID level 0x00000007:0 (ebx), word 9 */ diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c index 5774800..d315151 100644 --- a/arch/x86/xen/enlighten.c +++ b/arch/x86/xen/enlighten.c @@ -1886,8 +1886,10 @@ EXPORT_SYMBOL_GPL(xen_hvm_need_lapic); static void xen_set_cpu_features(struct cpuinfo_x86 *c) { - if (xen_pv_domain()) + if (xen_pv_domain()) { clear_cpu_bug(c, X86_BUG_SYSRET_SS_ATTRS); + set_cpu_cap(c, X86_FEATURE_XENPV); + } } const struct hypervisor_x86 x86_hyper_xen = { -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/