Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S966402AbcDLSJs (ORCPT ); Tue, 12 Apr 2016 14:09:48 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:49192 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1030383AbcDLSJp (ORCPT ); Tue, 12 Apr 2016 14:09:45 -0400 From: Luis Henriques To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: 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 , Luis Henriques Subject: [PATCH 3.16.y-ckt 14/17] x86/iopl/64: Properly context-switch IOPL on Xen PV Date: Tue, 12 Apr 2016 19:08:01 +0100 Message-Id: <1460484484-22395-15-git-send-email-luis.henriques@canonical.com> In-Reply-To: <1460484484-22395-1-git-send-email-luis.henriques@canonical.com> References: <1460484484-22395-1-git-send-email-luis.henriques@canonical.com> X-Extended-Stable: 3.16 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3543 Lines: 100 3.16.7-ckt27 -stable review patch. If anyone has any objections, please let me know. ---8<------------------------------------------------------------ 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 [ 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: Luis Henriques --- 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 e2072dc4b67a..a6f51ad11d89 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); @@ -427,6 +428,17 @@ __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 32d00ce4a194..e1e7f4f1fb80 100644 --- a/arch/x86/xen/enlighten.c +++ b/arch/x86/xen/enlighten.c @@ -956,7 +956,7 @@ 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;