Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932119AbcDZX2N (ORCPT ); Tue, 26 Apr 2016 19:28:13 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:41042 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754933AbcDZX2K (ORCPT ); Tue, 26 Apr 2016 19:28:10 -0400 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "H. Peter Anvin" , "Denys Vlasenko" , "Jan Beulich" , "Ingo Molnar" , "Boris Ostrovsky" , "Andy Lutomirski" , "Linus Torvalds" , "David Vrabel" , "Andrew Cooper" , "Borislav Petkov" , "Peter Zijlstra" , "Thomas Gleixner" , "Brian Gerst" , "Andy Lutomirski" Date: Wed, 27 Apr 2016 01:02:24 +0200 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.2 039/115] x86/iopl/64: Properly context-switch IOPL on Xen PV In-Reply-To: X-SA-Exim-Connect-IP: 2a02:8426:ae4:c500:9cba:69ae:962d:6167 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3158 Lines: 100 3.2.80-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Andy Lutomirski commit b7a584598aea7ca73140cb87b40319944dd3393f upstream. 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 Link: http://lkml.kernel.org/r/693c3bd7aeb4d3c27c92c622b7d0f554a458173c.1458162709.git.luto@kernel.org Signed-off-by: Ingo Molnar [bwh: Backported to 3.2: - Use xen_pv_domain() directly as X86_FEATURE_XENPV is not defined - Adjust context] Signed-off-by: Ben Hutchings --- 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(-) --- a/arch/x86/include/asm/xen/hypervisor.h +++ b/arch/x86/include/asm/xen/hypervisor.h @@ -72,4 +72,6 @@ static inline bool xen_x2apic_para_avail } #endif +extern void xen_set_iopl_mask(unsigned mask); + #endif /* _ASM_X86_XEN_HYPERVISOR_H */ --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -38,6 +38,7 @@ #include #include #include +#include #include #include @@ -52,6 +53,7 @@ #include #include #include +#include asmlinkage extern void ret_from_fork(void); @@ -518,6 +520,16 @@ __switch_to(struct task_struct *prev_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(xen_pv_domain() && prev->iopl != next->iopl)) + xen_set_iopl_mask(next->iopl); +#endif + return prev_p; } --- a/arch/x86/xen/enlighten.c +++ b/arch/x86/xen/enlighten.c @@ -768,7 +768,7 @@ static void xen_load_sp0(struct tss_stru xen_mc_issue(PARAVIRT_LAZY_CPU); } -static void xen_set_iopl_mask(unsigned mask) +void xen_set_iopl_mask(unsigned mask) { struct physdev_set_iopl set_iopl;