Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933562AbcDKNwW (ORCPT ); Mon, 11 Apr 2016 09:52:22 -0400 Received: from mx2.suse.de ([195.135.220.15]:37397 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932369AbcDKNX5 (ORCPT ); Mon, 11 Apr 2016 09:23:57 -0400 X-Amavis-Alert: BAD HEADER SECTION, Duplicate header field: "References" From: Jiri Slaby To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Andy Lutomirski , Andrew Cooper , Andy Lutomirski , Boris Ostrovsky , Borislav Petkov , Brian Gerst , David Vrabel , Denys Vlasenko , "H . Peter Anvin" , Jan Beulich , Linus Torvalds , Peter Zijlstra , Thomas Gleixner , Ingo Molnar , Kamal Mostafa , Jiri Slaby Subject: [PATCH 3.12 34/98] x86/iopl/64: Properly context-switch IOPL on Xen PV Date: Mon, 11 Apr 2016 15:22:36 +0200 Message-Id: X-Mailer: git-send-email 2.8.1 In-Reply-To: References: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3476 Lines: 102 From: Andy Lutomirski 3.12-stable review patch. If anyone has any objections, please let me know. =============== 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 [ kamal: backport to 3.19-stable: no X86_FEATURE_XENPV so just call xen_pv_domain() directly ] Acked-by: Andy Lutomirski Signed-off-by: Kamal Mostafa Signed-off-by: Jiri Slaby --- 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 d866959e5685..d2ad00a42234 100644 --- a/arch/x86/include/asm/xen/hypervisor.h +++ b/arch/x86/include/asm/xen/hypervisor.h @@ -57,4 +57,6 @@ static inline bool xen_x2apic_para_available(void) } #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 f99825ea4f96..5d4f6ccbae35 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -49,6 +49,7 @@ #include #include #include +#include asmlinkage extern void ret_from_fork(void); @@ -374,6 +375,17 @@ __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(xen_pv_domain() && + prev->iopl != next->iopl)) + xen_set_iopl_mask(next->iopl); +#endif + return prev_p; } diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c index b2de632861c2..7c8af5286549 100644 --- a/arch/x86/xen/enlighten.c +++ b/arch/x86/xen/enlighten.c @@ -955,7 +955,7 @@ static void xen_load_sp0(struct tss_struct *tss, 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; -- 2.8.1