From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932931AbdBVPgk (ORCPT ); Wed, 22 Feb 2017 10:36:40 -0500 Received: from mail.kernel.org ([198.145.29.136]:60478 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932836AbdBVPg0 (ORCPT ); Wed, 22 Feb 2017 10:36:26 -0500 From: Andy Lutomirski To: Paolo Bonzini , X86 ML Cc: kvm list , "linux-kernel@vger.kernel.org" , Borislav Petkov , Thomas Garnier , Jim Mattson , Andy Lutomirski Subject: [PATCH 1/2] x86/asm: Tidy up TSS limit code Date: Wed, 22 Feb 2017 07:36:16 -0800 Message-Id: <872bccdf5ff2b163eb00289cc3383170a0cef4de.1487777656.git.luto@kernel.org> X-Mailer: git-send-email 2.9.3 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 In an earlier version of the patch ("x86/kvm/vmx: Defer TR reload after VM exit") that introduced TSS limit validity tracking, I confused which helper was which. On reflection, the names I chose sucked. Rename the helpers to make it more obvious what's going on and add some comments. While I'm at it, clear __tss_limit_invalid when force-reloading as well as when contitionally reloading, since any TR reload fixes the limit. Signed-off-by: Andy Lutomirski --- arch/x86/include/asm/desc.h | 18 +++++++++++------- arch/x86/kernel/ioport.c | 8 +++++++- arch/x86/kernel/process.c | 6 +++--- 3 files changed, 21 insertions(+), 11 deletions(-) diff --git a/arch/x86/include/asm/desc.h b/arch/x86/include/asm/desc.h index cb8f9149f6c8..1548ca92ad3f 100644 --- a/arch/x86/include/asm/desc.h +++ b/arch/x86/include/asm/desc.h @@ -205,6 +205,8 @@ static inline void native_load_tr_desc(void) asm volatile("ltr %w0"::"q" (GDT_ENTRY_TSS*8)); } +DECLARE_PER_CPU(bool, __tss_limit_invalid); + static inline void force_reload_TR(void) { struct desc_struct *d = get_cpu_gdt_table(smp_processor_id()); @@ -220,18 +222,20 @@ static inline void force_reload_TR(void) write_gdt_entry(d, GDT_ENTRY_TSS, &tss, DESC_TSS); load_TR_desc(); + this_cpu_write(__tss_limit_invalid, false); } -DECLARE_PER_CPU(bool, need_tr_refresh); - -static inline void refresh_TR(void) +/* + * Call this if you need the TSS limit to be correct, which should be the case + * if and only if you have TIF_IO_BITMAP set or you're switching to a task + * with TIF_IO_BITMAP set. + */ +static inline void refresh_tss_limit(void) { DEBUG_LOCKS_WARN_ON(preemptible()); - if (unlikely(this_cpu_read(need_tr_refresh))) { + if (unlikely(this_cpu_read(__tss_limit_invalid))) force_reload_TR(); - this_cpu_write(need_tr_refresh, false); - } } /* @@ -250,7 +254,7 @@ static inline void invalidate_tss_limit(void) if (unlikely(test_thread_flag(TIF_IO_BITMAP))) force_reload_TR(); else - this_cpu_write(need_tr_refresh, true); + this_cpu_write(__tss_limit_invalid, true); } static inline void native_load_gdt(const struct desc_ptr *dtr) diff --git a/arch/x86/kernel/ioport.c b/arch/x86/kernel/ioport.c index b01bc8517450..875d3d25dd6a 100644 --- a/arch/x86/kernel/ioport.c +++ b/arch/x86/kernel/ioport.c @@ -47,8 +47,14 @@ asmlinkage long sys_ioperm(unsigned long from, unsigned long num, int turn_on) t->io_bitmap_ptr = bitmap; set_thread_flag(TIF_IO_BITMAP); + /* + * Now that we have an IO bitmap, we need our TSS limit to be + * correct. It's fine if we are preempted after doing this: + * with TIF_IO_BITMAP set, context switches will keep our TSS + * limit correct. + */ preempt_disable(); - refresh_TR(); + refresh_tss_limit(); preempt_enable(); } diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index 7780efa635b9..0b302591b51f 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -65,8 +65,8 @@ __visible DEFINE_PER_CPU_SHARED_ALIGNED(struct tss_struct, cpu_tss) = { }; EXPORT_PER_CPU_SYMBOL(cpu_tss); -DEFINE_PER_CPU(bool, need_tr_refresh); -EXPORT_PER_CPU_SYMBOL_GPL(need_tr_refresh); +DEFINE_PER_CPU(bool, __tss_limit_invalid); +EXPORT_PER_CPU_SYMBOL_GPL(__tss_limit_invalid); /* * this gets called so that we can store lazy state into memory and copy the @@ -218,7 +218,7 @@ void __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p, * Make sure that the TSS limit is correct for the CPU * to notice the IO bitmap. */ - refresh_TR(); + refresh_tss_limit(); } else if (test_tsk_thread_flag(prev_p, TIF_IO_BITMAP)) { /* * Clear any possible leftover bits: -- 2.9.3