From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8353DC2B9F4 for ; Mon, 14 Jun 2021 16:38:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6B6D7613CD for ; Mon, 14 Jun 2021 16:38:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235154AbhFNQk7 (ORCPT ); Mon, 14 Jun 2021 12:40:59 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:55792 "EHLO galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234853AbhFNQkP (ORCPT ); Mon, 14 Jun 2021 12:40:15 -0400 Message-Id: <20210614155355.841581418@linutronix.de> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1623688691; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: references:references; bh=ryPfX8yAG7C80O4zWnAr46k2Q5gfRQxnnp7gc/kjUrM=; b=MKh4bn7uvP72brFKvri7xZ0AN16CKCST3KQMOWAVuvS3Gcwrw9eUcYmDqtcr3caWG+BBCc kPo9yCKTzyGDvCuc+NuZrllzu2SWz8NwXgjKw/Tkof0hVBc0SdlxzQXmwYaJOt8t8KXH20 sjwovVg6Tgzk/sPMiXhjs/+GvLezqcN2y3Z7uporLX+MXxCGvNmP02r3t4MmorEshU33Cg PLfAekvVh2YbzOFDO0g+7u9S1J/MQNlLksKcReLKvaakmH/DK8Ph2ZP1NJeJMn+scSBzf8 VcfKfm1Tz0h2L1C6SkfhOlFQXIECIruulsi/cxermWud1qmc4/Lr9YjrO4+hCQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1623688691; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: references:references; bh=ryPfX8yAG7C80O4zWnAr46k2Q5gfRQxnnp7gc/kjUrM=; b=29YVNu2LD1h2fW25AnqHoTuzFZqBMgDwCMqr/JeNvq+HO54i1bD7C8XjLnZ1CsAHerFZZB ocOj3UltKC+lRYDA== Date: Mon, 14 Jun 2021 17:44:29 +0200 From: Thomas Gleixner To: LKML Cc: Andy Lutomirski , Dave Hansen , Fenghua Yu , Tony Luck , Yu-cheng Yu , Sebastian Andrzej Siewior , Borislav Petkov , Peter Zijlstra , Kan Liang Subject: [patch V2 21/52] x86/fpu: Get rid of copy_supervisor_to_kernel() References: <20210614154408.673478623@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-transfer-encoding: 8-bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org If the fast path of restoring the FPU state on sigreturn fails or is not taken and the current task's FPU is active then the FPU has to be deactivated for the slow path to allow a safe update of the tasks FPU memory state. With supervisor states enabled, this requires to save the supervisor state in the memory state first. Supervisor states require XSAVES so saving only the supervisor state requires to reshuffle the memory buffer because XSAVES uses the compacted format and therefore stores the supervisor states at the beginning of the memory state. That's just an overengineered optimization. Get rid of it and save the full state for this case. Signed-off-by: Thomas Gleixner Reviewed-by: Andy Lutomirski --- arch/x86/include/asm/fpu/xstate.h | 1 arch/x86/kernel/fpu/signal.c | 13 +++++--- arch/x86/kernel/fpu/xstate.c | 55 -------------------------------------- 3 files changed, 8 insertions(+), 61 deletions(-) --- a/arch/x86/include/asm/fpu/xstate.h +++ b/arch/x86/include/asm/fpu/xstate.h @@ -104,7 +104,6 @@ void *get_xsave_addr(struct xregs_state int xfeature_size(int xfeature_nr); int copy_kernel_to_xstate(struct xregs_state *xsave, const void *kbuf); int copy_user_to_xstate(struct xregs_state *xsave, const void __user *ubuf); -void copy_supervisor_to_kernel(struct xregs_state *xsave); void copy_dynamic_supervisor_to_kernel(struct xregs_state *xstate, u64 mask); void copy_kernel_to_dynamic_supervisor(struct xregs_state *xstate, u64 mask); --- a/arch/x86/kernel/fpu/signal.c +++ b/arch/x86/kernel/fpu/signal.c @@ -411,15 +411,18 @@ static int __fpu__restore_sig(void __use * the optimisation). */ fpregs_lock(); - if (!test_thread_flag(TIF_NEED_FPU_LOAD)) { - /* - * Supervisor states are not modified by user space input. Save - * current supervisor states first and invalidate the FPU regs. + * If supervisor states are available then save the + * hardware state in current's fpstate so that the + * supervisor state is preserved. Save the full state for + * simplicity. There is no point in optimizing this by only + * saving the supervisor states and then shuffle them to + * the right place in memory. This is the slow path and the + * above XRSTOR failed or ia32_fxstate is true. Shrug. */ if (xfeatures_mask_supervisor()) - copy_supervisor_to_kernel(&fpu->state.xsave); + copy_xregs_to_kernel(&fpu->state.xsave); set_thread_flag(TIF_NEED_FPU_LOAD); } __fpu_invalidate_fpregs_state(fpu); --- a/arch/x86/kernel/fpu/xstate.c +++ b/arch/x86/kernel/fpu/xstate.c @@ -1185,61 +1185,6 @@ int copy_user_to_xstate(struct xregs_sta return 0; } -/* - * Save only supervisor states to the kernel buffer. This blows away all - * old states, and is intended to be used only in __fpu__restore_sig(), where - * user states are restored from the user buffer. - */ -void copy_supervisor_to_kernel(struct xregs_state *xstate) -{ - struct xstate_header *header; - u64 max_bit, min_bit; - u32 lmask, hmask; - int err, i; - - if (WARN_ON(!boot_cpu_has(X86_FEATURE_XSAVES))) - return; - - if (!xfeatures_mask_supervisor()) - return; - - max_bit = __fls(xfeatures_mask_supervisor()); - min_bit = __ffs(xfeatures_mask_supervisor()); - - lmask = xfeatures_mask_supervisor(); - hmask = xfeatures_mask_supervisor() >> 32; - XSTATE_OP(XSAVES, xstate, lmask, hmask, err); - - /* We should never fault when copying to a kernel buffer: */ - if (WARN_ON_FPU(err)) - return; - - /* - * At this point, the buffer has only supervisor states and must be - * converted back to normal kernel format. - */ - header = &xstate->header; - header->xcomp_bv |= xfeatures_mask_all; - - /* - * This only moves states up in the buffer. Start with - * the last state and move backwards so that states are - * not overwritten until after they are moved. Note: - * memmove() allows overlapping src/dst buffers. - */ - for (i = max_bit; i >= min_bit; i--) { - u8 *xbuf = (u8 *)xstate; - - if (!((header->xfeatures >> i) & 1)) - continue; - - /* Move xfeature 'i' into its normal location */ - memmove(xbuf + xstate_comp_offsets[i], - xbuf + xstate_supervisor_only_offsets[i], - xstate_sizes[i]); - } -} - /** * copy_dynamic_supervisor_to_kernel() - Save dynamic supervisor states to * an xsave area