From patchwork Wed Jan 29 09:58:57 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Adrian Hunter X-Patchwork-Id: 13953586 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.12]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A98ED1D8E10; Wed, 29 Jan 2025 10:00:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.175.65.12 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738144818; cv=none; b=rccGp37px4MzUw+m4yxfTpTRrnR3HQl7cuEbCGxfHv5J7WEXp6YRPVW+C8L9OO4d1fXsAZ5gYkQPdrcyP7t77IojzZPMVsgKbUcNlOQLOjjSP42p6In+glI+CTiklAkOVlfNvnLQ243dAemah+SJL74stTwjRXoVkKbG8IH9UfQ= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738144818; c=relaxed/simple; bh=g2KLE8NL4H2nXqxB/6OS8EevoKIgyR/mQRghF7+qh/c=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=hdDO8/y9qOK/aWjP0qmIo/k6CZTN6FoOUexNkm+Er99mOfpsYhgjnh3D6SJS84j/6jzwyEsg07ghi5MNwuXL5/WFQHtAa8IIBx8oUo1Gt5WlvS0+idw2GtUoT+yIGpXF9g2OkTT2w152kgfrd0ygic6/hd2VBV+fS0xrrLJM8dY= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com; spf=pass smtp.mailfrom=intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=DDd3xArD; arc=none smtp.client-ip=198.175.65.12 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="DDd3xArD" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1738144817; x=1769680817; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=g2KLE8NL4H2nXqxB/6OS8EevoKIgyR/mQRghF7+qh/c=; b=DDd3xArDF6LarxP8O9+77FODwvkSbrT0qvYSa5zDeteFfuOczZlgVIvl K3qFK61dRz6CSxRP33tFpn/TbHrrwleQSNpzhm6yglLQmF1D2V9bWUg4W xqnRZyq2+WseSf6eaaLc3s5SDPbxi//JfdNRXyIGD8uyro13+7+dyRGxN x2tDlLQ8XvgTFafiagME2/csvNw6L4KWiMyo7QZwOkxz82Kz63rNaNbR/ eUVwVlbdnBeQdhdeHInlqQnQ7CxZFdycI/VNZUcDbBg3yHGCH7ZRe3mc9 L0EeD4eI7QUpcqZEk+E2omN1SRt4vOf/gQY8/YlGcqTagb0Ht8JYwTQMc A==; X-CSE-ConnectionGUID: z8cpku4cQR6kaItT7qLbkw== X-CSE-MsgGUID: Vxtw0s44Qs+cFlJvQZCTrg== X-IronPort-AV: E=McAfee;i="6700,10204,11329"; a="50036049" X-IronPort-AV: E=Sophos;i="6.13,243,1732608000"; d="scan'208";a="50036049" Received: from fmviesa002.fm.intel.com ([10.60.135.142]) by orvoesa104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 Jan 2025 01:59:58 -0800 X-CSE-ConnectionGUID: EBUctnx8TpehHWWb8YtJug== X-CSE-MsgGUID: xPO305oyQjag+yo4xyM9sA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.12,224,1728975600"; d="scan'208";a="132262704" Received: from ahunter6-mobl1.ger.corp.intel.com (HELO ahunter-VirtualBox.ger.corp.intel.com) ([10.246.0.178]) by fmviesa002-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 Jan 2025 01:59:54 -0800 From: Adrian Hunter To: pbonzini@redhat.com, seanjc@google.com Cc: kvm@vger.kernel.org, rick.p.edgecombe@intel.com, kai.huang@intel.com, adrian.hunter@intel.com, reinette.chatre@intel.com, xiaoyao.li@intel.com, tony.lindgren@linux.intel.com, binbin.wu@linux.intel.com, dmatlack@google.com, isaku.yamahata@intel.com, nik.borisov@suse.com, linux-kernel@vger.kernel.org, yan.y.zhao@intel.com, chao.gao@intel.com, weijiang.yang@intel.com Subject: [PATCH V2 08/12] KVM: x86: Allow to update cached values in kvm_user_return_msrs w/o wrmsr Date: Wed, 29 Jan 2025 11:58:57 +0200 Message-ID: <20250129095902.16391-9-adrian.hunter@intel.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20250129095902.16391-1-adrian.hunter@intel.com> References: <20250129095902.16391-1-adrian.hunter@intel.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Organization: Intel Finland Oy, Registered Address: PL 281, 00181 Helsinki, Business Identity Code: 0357606 - 4, Domiciled in Helsinki From: Chao Gao Several MSRs are constant and only used in userspace(ring 3). But VMs may have different values. KVM uses kvm_set_user_return_msr() to switch to guest's values and leverages user return notifier to restore them when the kernel is to return to userspace. To eliminate unnecessary wrmsr, KVM also caches the value it wrote to an MSR last time. TDX module unconditionally resets some of these MSRs to architectural INIT state on TD exit. It makes the cached values in kvm_user_return_msrs are inconsistent with values in hardware. This inconsistency needs to be fixed. Otherwise, it may mislead kvm_on_user_return() to skip restoring some MSRs to the host's values. kvm_set_user_return_msr() can help correct this case, but it is not optimal as it always does a wrmsr. So, introduce a variation of kvm_set_user_return_msr() to update cached values and skip that wrmsr. Signed-off-by: Chao Gao Signed-off-by: Isaku Yamahata Signed-off-by: Adrian Hunter Reviewed-by: Paolo Bonzini --- TD vcpu enter/exit v2: - No changes TD vcpu enter/exit v1: - Rename functions and remove useless comment (Binbin) --- arch/x86/include/asm/kvm_host.h | 1 + arch/x86/kvm/x86.c | 24 +++++++++++++++++++----- 2 files changed, 20 insertions(+), 5 deletions(-) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 6b686d62c735..e557a441fade 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -2322,6 +2322,7 @@ int kvm_pv_send_ipi(struct kvm *kvm, unsigned long ipi_bitmap_low, int kvm_add_user_return_msr(u32 msr); int kvm_find_user_return_msr(u32 msr); int kvm_set_user_return_msr(unsigned index, u64 val, u64 mask); +void kvm_user_return_msr_update_cache(unsigned int index, u64 val); static inline bool kvm_is_supported_user_return_msr(u32 msr) { diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 5cf9f023fd4b..15447fe7687c 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -636,6 +636,15 @@ static void kvm_user_return_msr_cpu_online(void) } } +static void kvm_user_return_register_notifier(struct kvm_user_return_msrs *msrs) +{ + if (!msrs->registered) { + msrs->urn.on_user_return = kvm_on_user_return; + user_return_notifier_register(&msrs->urn); + msrs->registered = true; + } +} + int kvm_set_user_return_msr(unsigned slot, u64 value, u64 mask) { struct kvm_user_return_msrs *msrs = this_cpu_ptr(user_return_msrs); @@ -649,15 +658,20 @@ int kvm_set_user_return_msr(unsigned slot, u64 value, u64 mask) return 1; msrs->values[slot].curr = value; - if (!msrs->registered) { - msrs->urn.on_user_return = kvm_on_user_return; - user_return_notifier_register(&msrs->urn); - msrs->registered = true; - } + kvm_user_return_register_notifier(msrs); return 0; } EXPORT_SYMBOL_GPL(kvm_set_user_return_msr); +void kvm_user_return_msr_update_cache(unsigned int slot, u64 value) +{ + struct kvm_user_return_msrs *msrs = this_cpu_ptr(user_return_msrs); + + msrs->values[slot].curr = value; + kvm_user_return_register_notifier(msrs); +} +EXPORT_SYMBOL_GPL(kvm_user_return_msr_update_cache); + static void drop_user_return_notifiers(void) { struct kvm_user_return_msrs *msrs = this_cpu_ptr(user_return_msrs);