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[23.128.96.18]) by mx.google.com with ESMTP id p15si17218218ilo.83.2021.05.10.01.53.06; Mon, 10 May 2021 01:53:19 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=lOzjSy0N; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230160AbhEJIwg (ORCPT + 99 others); Mon, 10 May 2021 04:52:36 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44446 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229566AbhEJIwf (ORCPT ); Mon, 10 May 2021 04:52:35 -0400 Received: from mail-ot1-x32d.google.com (mail-ot1-x32d.google.com [IPv6:2607:f8b0:4864:20::32d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9B8C7C061573; Mon, 10 May 2021 01:51:30 -0700 (PDT) Received: by mail-ot1-x32d.google.com with SMTP id d3-20020a9d29030000b029027e8019067fso13734052otb.13; Mon, 10 May 2021 01:51:30 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=+r8BVxHk1L3blGKpgXCIc2S1WgCsup6Bh4KC+edeS3k=; b=lOzjSy0Ncj10m2t9syUMAtwu2shOjfAIyyTVlt9DK4D4QIBi/X1gLtnIru/pUwaAQQ l13Jsl4sdulSWQw9dJpq1uVFC6f54kOT6hqHwxZiyvPBNu0GRzKXQpdP40vAleigw09g XMARzKwa1jWyOxUWFnEI24JPaMXosvtDFV+h+TUZtTJZPOBvhCccOYOhKytIoxSPYTKK fnkqZIXqam0P8tyUXxHmwZeJ2IVVAswxA7DgDUYSKsxFRMLJFpe8NMhaADrfhmjKbQ4j kSKXmFNysKxMLuk1dNti7aCKHqCC1pNiPAKFyQn86x3mQNQE+oRiP0FcPxUJdEPFB2If f96w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=+r8BVxHk1L3blGKpgXCIc2S1WgCsup6Bh4KC+edeS3k=; b=iki8R6MbALN8vti2pIIPTI3J27Ni5Y1ckbSs+QmmfilQJOEAD7acNgVeQBFY9IBeMu tUxiFAjWe4ppRB+GAker8y2ScCcXv1+tGPUmbH+5639cnQPLyLDTQTU+ZJLU15TuOsAZ B7lgWDJF5Fm0QI3SOj9rgiLQXcPLSI6D2wRo9EkY5dsLK3Utlu5F9GEEcTw2Lv4aW2T6 nEarISwt4MOLfY7vjfiyE+5/PXYurcBKamFsa4fES24PkToB2jJTguROUDacklNyL142 /TB8IawYVKmB6UXhtSlrwL8aC9l0/pFisfEfgsFrwg2OeMqFh028u8rln7E4eGqNAfVy adkg== X-Gm-Message-State: AOAM531bQcmo2BF1Jc4GB/H1AkOyihX5QfPItst1GwNXdvciXxy1nPKg rIqx6kULstr/TNfSSPnhdw+WywkcZzNFV4XvwZA= X-Received: by 2002:a05:6830:16c8:: with SMTP id l8mr20327751otr.56.1620636690072; Mon, 10 May 2021 01:51:30 -0700 (PDT) MIME-Version: 1.0 References: <1620634919-4563-1-git-send-email-wanpengli@tencent.com> <87mtt3vus5.fsf@vitty.brq.redhat.com> In-Reply-To: <87mtt3vus5.fsf@vitty.brq.redhat.com> From: Wanpeng Li Date: Mon, 10 May 2021 16:51:19 +0800 Message-ID: Subject: Re: [PATCH] KVM: x86: hyper-v: Task srcu lock when accessing kvm_memslots() To: Vitaly Kuznetsov Cc: Paolo Bonzini , Sean Christopherson , Wanpeng Li , Jim Mattson , Joerg Roedel , LKML , kvm Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 10 May 2021 at 16:48, Vitaly Kuznetsov wrote: > > Wanpeng Li writes: > > > From: Wanpeng Li > > > > WARNING: suspicious RCU usage > > 5.13.0-rc1 #4 Not tainted > > ----------------------------- > > ./include/linux/kvm_host.h:710 suspicious rcu_dereference_check() usage! > > > > other info that might help us debug this: > > > > rcu_scheduler_active = 2, debug_locks = 1 > > 1 lock held by hyperv_clock/8318: > > #0: ffffb6b8cb05a7d8 (&hv->hv_lock){+.+.}-{3:3}, at: kvm_hv_invalidate_tsc_page+0x3e/0xa0 [kvm] > > > > stack backtrace: > > CPU: 3 PID: 8318 Comm: hyperv_clock Not tainted 5.13.0-rc1 #4 > > Call Trace: > > dump_stack+0x87/0xb7 > > lockdep_rcu_suspicious+0xce/0xf0 > > kvm_write_guest_page+0x1c1/0x1d0 [kvm] > > kvm_write_guest+0x50/0x90 [kvm] > > kvm_hv_invalidate_tsc_page+0x79/0xa0 [kvm] > > kvm_gen_update_masterclock+0x1d/0x110 [kvm] > > kvm_arch_vm_ioctl+0x2a7/0xc50 [kvm] > > kvm_vm_ioctl+0x123/0x11d0 [kvm] > > __x64_sys_ioctl+0x3ed/0x9d0 > > do_syscall_64+0x3d/0x80 > > entry_SYSCALL_64_after_hwframe+0x44/0xae > > > > kvm_memslots() will be called by kvm_write_guest(), so we should take the srcu lock. > > > > Fixes: e880c6ea5 (KVM: x86: hyper-v: Prevent using not-yet-updated TSC page by secondary CPUs) > > Signed-off-by: Wanpeng Li > > --- > > arch/x86/kvm/hyperv.c | 8 ++++++++ > > 1 file changed, 8 insertions(+) > > > > diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c > > index f98370a3..f00830e 100644 > > --- a/arch/x86/kvm/hyperv.c > > +++ b/arch/x86/kvm/hyperv.c > > @@ -1172,6 +1172,7 @@ void kvm_hv_invalidate_tsc_page(struct kvm *kvm) > > { > > struct kvm_hv *hv = to_kvm_hv(kvm); > > u64 gfn; > > + int idx; > > > > if (hv->hv_tsc_page_status == HV_TSC_PAGE_BROKEN || > > hv->hv_tsc_page_status == HV_TSC_PAGE_UNSET || > > @@ -1190,9 +1191,16 @@ void kvm_hv_invalidate_tsc_page(struct kvm *kvm) > > gfn = hv->hv_tsc_page >> HV_X64_MSR_TSC_REFERENCE_ADDRESS_SHIFT; > > > > hv->tsc_ref.tsc_sequence = 0; > > + > > + /* > > + * Take the srcu lock as memslots will be accessed to check the gfn > > + * cache generation against the memslots generation. > > + */ > > + idx = srcu_read_lock(&kvm->srcu); > > if (kvm_write_guest(kvm, gfn_to_gpa(gfn), > > &hv->tsc_ref, sizeof(hv->tsc_ref.tsc_sequence))) > > hv->hv_tsc_page_status = HV_TSC_PAGE_BROKEN; > > + srcu_read_unlock(&kvm->srcu, idx); > > > > out_unlock: > > mutex_unlock(&hv->hv_lock); > > Thanks! > > Do we need to do the same in kvm_hv_setup_tsc_page()? kvm_hv_setup_tsc_page() is called in vcpu_enter_guest() path which has already held kvm->srcu lock. Wanpeng