From patchwork Wed Dec 29 13:13:27 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yang Zhong X-Patchwork-Id: 12700924 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 9073DC4332F for ; Wed, 29 Dec 2021 13:15:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240389AbhL2NPo (ORCPT ); Wed, 29 Dec 2021 08:15:44 -0500 Received: from mga07.intel.com ([134.134.136.100]:28053 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240427AbhL2NPL (ORCPT ); Wed, 29 Dec 2021 08:15:11 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1640783711; x=1672319711; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=SCKjPPW63mIUiKQ82zQmlY37BU1ztFvuBfN2C/bj1WY=; b=TSgxsCZqq8Fl1HOTV4399Oc+4jhy9uogDpCoLqYSrFZkCt1X8PqC0JD2 v30gqaTaMQpSmoGFaauqwyVjoVS48iz15Cq+FvGZsxsA4GMhyj5njXaaz TzVyxINdpjlqfJp1ph/8urkcvf2ke1YBkFl0wwhdYscw8NY4dZt8o46KS moWCQwdbz4agF6YDw/1m0j4prVypg9Z2tFVm1eLOgROaLwGBqGtSQjv95 6IMdpKWo073G652ySuKEIOXk1u6z3W41O61RIqzs/Ezcv8qI9DRjq5wMQ f1KfP5pP1G6x11QSixNQPFv8Py68FM1FLUwNuBd/aenagsTpGGlAZ6c01 g==; X-IronPort-AV: E=McAfee;i="6200,9189,10211"; a="304876169" X-IronPort-AV: E=Sophos;i="5.88,245,1635231600"; d="scan'208";a="304876169" Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by orsmga105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 Dec 2021 05:13:44 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.88,245,1635231600"; d="scan'208";a="666281224" Received: from 984fee00bf64.jf.intel.com ([10.165.54.77]) by fmsmga001.fm.intel.com with ESMTP; 29 Dec 2021 05:13:44 -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 Cc: seanjc@google.com, 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 v4 20/21] x86/fpu: Provide fpu_sync_guest_vmexit_xfd_state() Date: Wed, 29 Dec 2021 05:13:27 -0800 Message-Id: <20211229131328.12283-21-yang.zhong@intel.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20211229131328.12283-1-yang.zhong@intel.com> References: <20211229131328.12283-1-yang.zhong@intel.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: kvm@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 100b535cd3de..dc51809f0e4a 100644 --- a/arch/x86/include/asm/fpu/api.h +++ b/arch/x86/include/asm/fpu/api.h @@ -142,8 +142,10 @@ extern int fpu_update_guest_perm_features(struct fpu_guest *guest_fpu); #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 89d679cc819b..42a195a6b2ce 100644 --- a/arch/x86/kernel/fpu/core.c +++ b/arch/x86/kernel/fpu/core.c @@ -299,6 +299,30 @@ 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)