From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935393AbcCQJWh (ORCPT ); Thu, 17 Mar 2016 05:22:37 -0400 Received: from terminus.zytor.com ([198.137.202.10]:39004 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932853AbcCQJUj (ORCPT ); Thu, 17 Mar 2016 05:20:39 -0400 Date: Thu, 17 Mar 2016 02:19:12 -0700 From: tip-bot for Andy Lutomirski Message-ID: Cc: luto@kernel.org, peterz@infradead.org, dvlasenk@redhat.com, luto@amacapital.net, brgerst@gmail.com, andrew.cooper3@citrix.com, linux-kernel@vger.kernel.org, bp@alien8.de, david.vrabel@citrix.com, JBeulich@suse.com, torvalds@linux-foundation.org, hpa@zytor.com, tglx@linutronix.de, boris.ostrovsky@oracle.com, mingo@kernel.org Reply-To: bp@alien8.de, brgerst@gmail.com, luto@amacapital.net, andrew.cooper3@citrix.com, linux-kernel@vger.kernel.org, luto@kernel.org, dvlasenk@redhat.com, peterz@infradead.org, tglx@linutronix.de, boris.ostrovsky@oracle.com, mingo@kernel.org, hpa@zytor.com, david.vrabel@citrix.com, JBeulich@suse.com, torvalds@linux-foundation.org In-Reply-To: <693c3bd7aeb4d3c27c92c622b7d0f554a458173c.1458162709.git.luto@kernel.org> References: <693c3bd7aeb4d3c27c92c622b7d0f554a458173c.1458162709.git.luto@kernel.org> To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/urgent] x86/iopl/64: Properly context-switch IOPL on Xen PV Git-Commit-ID: b7a584598aea7ca73140cb87b40319944dd3393f 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 Commit-ID: b7a584598aea7ca73140cb87b40319944dd3393f Gitweb: http://git.kernel.org/tip/b7a584598aea7ca73140cb87b40319944dd3393f Author: Andy Lutomirski AuthorDate: Wed, 16 Mar 2016 14:14:21 -0700 Committer: Ingo Molnar CommitDate: Thu, 17 Mar 2016 09:49:26 +0100 x86/iopl/64: Properly context-switch IOPL on Xen PV On Xen PV, regs->flags doesn't reliably reflect IOPL and the exit-to-userspace code doesn't change IOPL. We need to context switch it manually. I'm doing this without going through paravirt because this is specific to Xen PV. After the dust settles, we can merge this with the 32-bit code, tidy up the iopl syscall implementation, and remove the set_iopl pvop entirely. Fixes XSA-171. Reviewewd-by: Jan Beulich Signed-off-by: Andy Lutomirski Cc: Andrew Cooper Cc: Andy Lutomirski Cc: Boris Ostrovsky Cc: Borislav Petkov Cc: Brian Gerst Cc: David Vrabel Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Jan Beulich Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: stable@vger.kernel.org Link: http://lkml.kernel.org/r/693c3bd7aeb4d3c27c92c622b7d0f554a458173c.1458162709.git.luto@kernel.org Signed-off-by: Ingo Molnar --- arch/x86/include/asm/xen/hypervisor.h | 2 ++ arch/x86/kernel/process_64.c | 12 ++++++++++++ arch/x86/xen/enlighten.c | 2 +- 3 files changed, 15 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/asm/xen/hypervisor.h b/arch/x86/include/asm/xen/hypervisor.h index 8b2d4be..39171b3 100644 --- a/arch/x86/include/asm/xen/hypervisor.h +++ b/arch/x86/include/asm/xen/hypervisor.h @@ -62,4 +62,6 @@ void xen_arch_register_cpu(int num); void xen_arch_unregister_cpu(int num); #endif +extern void xen_set_iopl_mask(unsigned mask); + #endif /* _ASM_X86_XEN_HYPERVISOR_H */ diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c index b9d99e0..9f75187 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -48,6 +48,7 @@ #include #include #include +#include asmlinkage extern void ret_from_fork(void); @@ -411,6 +412,17 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p) task_thread_info(prev_p)->flags & _TIF_WORK_CTXSW_PREV)) __switch_to_xtra(prev_p, next_p, tss); +#ifdef CONFIG_XEN + /* + * On Xen PV, IOPL bits in pt_regs->flags have no effect, and + * current_pt_regs()->flags may not match the current task's + * intended IOPL. We need to switch it manually. + */ + if (unlikely(static_cpu_has(X86_FEATURE_XENPV) && + prev->iopl != next->iopl)) + xen_set_iopl_mask(next->iopl); +#endif + if (static_cpu_has_bug(X86_BUG_SYSRET_SS_ATTRS)) { /* * AMD CPUs have a misfeature: SYSRET sets the SS selector but diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c index 2c26108..8381fb9 100644 --- a/arch/x86/xen/enlighten.c +++ b/arch/x86/xen/enlighten.c @@ -961,7 +961,7 @@ static void xen_load_sp0(struct tss_struct *tss, tss->x86_tss.sp0 = thread->sp0; } -static void xen_set_iopl_mask(unsigned mask) +void xen_set_iopl_mask(unsigned mask) { struct physdev_set_iopl set_iopl;