From patchwork Wed Jan 5 12:35:31 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yang Zhong X-Patchwork-Id: 530583 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 18B52C433F5 for ; Wed, 5 Jan 2022 12:36:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240352AbiAEMgy (ORCPT ); Wed, 5 Jan 2022 07:36:54 -0500 Received: from mga04.intel.com ([192.55.52.120]:6468 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240132AbiAEMgM (ORCPT ); Wed, 5 Jan 2022 07:36:12 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1641386172; x=1672922172; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=uwB8Do+UvWSqh1uXxIm79BiFywBVJAvYlaqDQK4oaUs=; b=nmf7sKGD3g/BxZxpP3Zu/VkqIekJ0+VLK2044WeojgMKV1J4OFhcYR3a QHyMruUbKPXiXvyVjNWvFc9lsX4W6bds06OW1iIz31VmprPQsXd07vmZp ij0jZ1VUA+owV4Xk80Kiq1V0i4ymsMiUaGLd6fuXl+kuHzfyNkrKRbEwY DRrfzoFhE2sCGF8rYHN3YWTW50Nf0NVNdnux1waZmN90zcBUZThZqy9Yc rLHbrD3PgL56sjPr/NeVL81ENcdObTsh6tly9NrMLeU1cgz5O5XV8FCi2 VEmq4m+gp9CKVnUuJOp61mDRI1XDJkBuEprRsgM2xR0wmiueBWmu6mKge g==; X-IronPort-AV: E=McAfee;i="6200,9189,10217"; a="241249394" X-IronPort-AV: E=Sophos;i="5.88,263,1635231600"; d="scan'208";a="241249394" Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by fmsmga104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 05 Jan 2022 04:35:43 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.88,263,1635231600"; d="scan'208";a="591004900" Received: from 984fee00bf64.jf.intel.com ([10.165.54.77]) by fmsmga004.fm.intel.com with ESMTP; 05 Jan 2022 04:35:43 -0800 From: Yang Zhong To: x86@kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, pbonzini@redhat.com, corbet@lwn.net, shuah@kernel.org, seanjc@google.com Cc: jun.nakajima@intel.com, kevin.tian@intel.com, jing2.liu@linux.intel.com, jing2.liu@intel.com, guang.zeng@intel.com, wei.w.wang@intel.com, yang.zhong@intel.com Subject: [PATCH v5 20/21] x86/fpu: Provide fpu_sync_guest_vmexit_xfd_state() Date: Wed, 5 Jan 2022 04:35:31 -0800 Message-Id: <20220105123532.12586-21-yang.zhong@intel.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20220105123532.12586-1-yang.zhong@intel.com> References: <20220105123532.12586-1-yang.zhong@intel.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org From: Thomas Gleixner KVM can disable the write emulation for the XFD MSR when the vCPU's fpstate is already correctly sized to reduce the overhead. When write emulation is disabled the XFD MSR state after a VMEXIT is unknown and therefore not in sync with the software states in fpstate and the per CPU XFD cache. Provide fpu_sync_guest_vmexit_xfd_state() which has to be invoked after a VMEXIT before enabling interrupts when write emulation is disabled for the XFD MSR. It could be invoked unconditionally even when write emulation is enabled for the price of a pointless MSR read. Signed-off-by: Thomas Gleixner Signed-off-by: Jing Liu Signed-off-by: Yang Zhong --- arch/x86/include/asm/fpu/api.h | 2 ++ arch/x86/kernel/fpu/core.c | 24 ++++++++++++++++++++++++ 2 files changed, 26 insertions(+) diff --git a/arch/x86/include/asm/fpu/api.h b/arch/x86/include/asm/fpu/api.h index e4d10155290b..a467eb80f9ed 100644 --- a/arch/x86/include/asm/fpu/api.h +++ b/arch/x86/include/asm/fpu/api.h @@ -142,8 +142,10 @@ extern int fpu_enable_guest_xfd_features(struct fpu_guest *guest_fpu, u64 xfeatu #ifdef CONFIG_X86_64 extern void fpu_update_guest_xfd(struct fpu_guest *guest_fpu, u64 xfd); +extern void fpu_sync_guest_vmexit_xfd_state(void); #else static inline void fpu_update_guest_xfd(struct fpu_guest *guest_fpu, u64 xfd) { } +static inline void fpu_sync_guest_vmexit_xfd_state(void) { } #endif extern void fpu_copy_guest_fpstate_to_uabi(struct fpu_guest *gfpu, void *buf, unsigned int size, u32 pkru); diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c index 5e7de79c1fe1..e5dfd8b9825a 100644 --- a/arch/x86/kernel/fpu/core.c +++ b/arch/x86/kernel/fpu/core.c @@ -289,6 +289,30 @@ void fpu_update_guest_xfd(struct fpu_guest *guest_fpu, u64 xfd) fpregs_unlock(); } EXPORT_SYMBOL_GPL(fpu_update_guest_xfd); + +/** + * fpu_sync_guest_vmexit_xfd_state - Synchronize XFD MSR and software state + * + * Must be invoked from KVM after a VMEXIT before enabling interrupts when + * XFD write emulation is disabled. This is required because the guest can + * freely modify XFD and the state at VMEXIT is not guaranteed to be the + * same as the state on VMENTER. So software state has to be udpated before + * any operation which depends on it can take place. + * + * Note: It can be invoked unconditionally even when write emulation is + * enabled for the price of a then pointless MSR read. + */ +void fpu_sync_guest_vmexit_xfd_state(void) +{ + struct fpstate *fps = current->thread.fpu.fpstate; + + lockdep_assert_irqs_disabled(); + if (fpu_state_size_dynamic()) { + rdmsrl(MSR_IA32_XFD, fps->xfd); + __this_cpu_write(xfd_state, fps->xfd); + } +} +EXPORT_SYMBOL_GPL(fpu_sync_guest_vmexit_xfd_state); #endif /* CONFIG_X86_64 */ int fpu_swap_kvm_fpstate(struct fpu_guest *guest_fpu, bool enter_guest)