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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8A3BEC433FE for ; Wed, 30 Mar 2022 16:52:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1349067AbiC3Qyj (ORCPT ); Wed, 30 Mar 2022 12:54:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43958 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1349057AbiC3Qyg (ORCPT ); Wed, 30 Mar 2022 12:54:36 -0400 Received: from mail-qt1-x829.google.com (mail-qt1-x829.google.com [IPv6:2607:f8b0:4864:20::829]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AC79B295266 for ; Wed, 30 Mar 2022 09:52:49 -0700 (PDT) Received: by mail-qt1-x829.google.com with SMTP id t2so18582151qtw.9 for ; Wed, 30 Mar 2022 09:52:49 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=XJOuIwKVKJoYxuu3h/fPqnOnXuAJfnfjZiDXXpn0snE=; b=W0nG8AGf+ASsomfq42TBWSEBx2Dz6O4Miy4mAlrPzEN13GB02uiM9eIQmcfsrRmKJy K14YOXl/gyqUhfC8SZpnIYmCSA2nUwyYmRIxeZ43f4Q+4MFmPt7QnfvxQAhpWg+TUOMv ac9Bc7b9HAra3K77FCcgbfXQDGQ9KzvaApqiyR5yX6BCD/PhgTvL9Nj/v92Zn4OcLP2W +DcbNv9CdksYxkikiGVKJ06/QIKYnvePM0ohzyyAa95b/BqQYHhZlEgWU7JoDJ4ZrtEw uZedmaUwRdAtByYuFrqllvZv3R4Asz0MmYMV19PihXeatj/WxYMr6eQ25lMpfxhMBEPR /yZw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc:content-transfer-encoding; bh=XJOuIwKVKJoYxuu3h/fPqnOnXuAJfnfjZiDXXpn0snE=; b=t9XcAHMdd2rdht7c+/9aFMd1RsPuWhtH6bbhVhG+VtRqMOz63wYzHvNbJippEeyKwA vOwkrJQ2rkHXAgUuOkCXNPIpZjWCdHQDwaQhP4/I8gVTSpbLzsGZGxAduGPKDr7eq39T sGwRSz+MjWWcMsu8e7BemVsxYcgF9RZ7JyzPoxr1DPMRd71tOPzQXnMbvI+i9WGIwUw0 QyeFWRQtgxrvzNnPCwIg59Y5M89j7tsLcex7tOZINPJrwhO0FRIgYyM4h7exzmGTEhX1 ePAL649LJuX5/wzIoSReZ5VREtPxwacnZ6RnME2QUeRnjMven3HDvfQuiNDYTKYxYNXd iZBA== X-Gm-Message-State: AOAM530+I1KtITRrXirUr/167C6RwxqotHl/8KFGU2TH0w8xm8uFmHF9 eZK2rq4RsX+mE30kAHmgkSZezIwcV8rj5AK/Zl+GgA== X-Google-Smtp-Source: ABdhPJwTrFJQcKlABPDFC6SiWpCj+tgomGjgZ5zXjm8Ti9j9sbsIZeHmmhCLKE6Z1MO+rFlvQQBkuLfnHplv46iq6wo= X-Received: by 2002:ac8:5aca:0:b0:2e1:e117:b2ff with SMTP id d10-20020ac85aca000000b002e1e117b2ffmr441196qtd.410.1648659168628; Wed, 30 Mar 2022 09:52:48 -0700 (PDT) MIME-Version: 1.0 References: <20220330164306.2376085-1-pgonda@google.com> In-Reply-To: <20220330164306.2376085-1-pgonda@google.com> From: Mingwei Zhang Date: Wed, 30 Mar 2022 09:52:37 -0700 Message-ID: Subject: Re: [PATCH] KVM: SEV: Add cond_resched() to loop in sev_clflush_pages() To: Peter Gonda Cc: kvm , Sean Christopherson , LKML Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Mar 30, 2022 at 9:43 AM Peter Gonda wrote: > > Add resched to avoid warning from sev_clflush_pages() with large number > of pages. > > Signed-off-by: Peter Gonda > Cc: Sean Christopherson > Cc: kvm@vger.kernel.org > Cc: linux-kernel@vger.kernel.org > > --- > Here is a warning similar to what I've seen many times running large SEV > VMs: > [ 357.714051] CPU 15: need_resched set for > 52000222 ns (52 ticks) with= out schedule > [ 357.721623] WARNING: CPU: 15 PID: 35848 at kernel/sched/core.c:3733 sc= heduler_tick+0x2f9/0x3f0 > [ 357.730222] Modules linked in: kvm_amd uhaul vfat fat hdi2_standard_ft= l hdi2_megablocks hdi2_pmc hdi2_pmc_eeprom hdi2 stg elephant_dev_num ccp i2= c_mux_ltc4306 i2c_mux i2c_via_ipmi i2c_piix4 google_bmc_usb google_bmc_gpio= i2c_mb_common google_bmc_mailbox cdc_acm xhci_pci xhci_hcd sha3_generic gq = nv_p2p_glue accel_class > [ 357.758261] CPU: 15 PID: 35848 Comm: switchto-defaul Not tainted 4.15.= 0-smp-DEV #11 > [ 357.765912] Hardware name: Google, Inc. = Arcadia_IT_80/Arcadia_IT_80, BIOS 30.20.2-gce 11/05= /2021 > [ 357.779372] RIP: 0010:scheduler_tick+0x2f9/0x3f0 > [ 357.783988] RSP: 0018:ffff98558d1c3dd8 EFLAGS: 00010046 > [ 357.789207] RAX: 741f23206aa8dc00 RBX: 0000005349236a42 RCX: 000000000= 0000007 > [ 357.796339] RDX: 0000000000000006 RSI: 0000000000000002 RDI: ffff98558= d1d5a98 > [ 357.803463] RBP: ffff98558d1c3ea0 R08: 0000000000100ceb R09: 000000000= 0000000 > [ 357.810597] R10: ffff98558c958c00 R11: ffffffff94850740 R12: 000000000= 31975de > [ 357.817729] R13: 0000000000000000 R14: ffff98558d1e2640 R15: ffff98525= 739ea40 > [ 357.824862] FS: 00007f87503eb700(0000) GS:ffff98558d1c0000(0000) knlG= S:0000000000000000 > [ 357.832948] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [ 357.838695] CR2: 00005572fe74b080 CR3: 0000007bea706006 CR4: 000000000= 0360ef0 > [ 357.845828] Call Trace: > [ 357.848277] > [ 357.850294] [] ? tick_setup_sched_timer+0x130/0x130 > [ 357.856818] [] ? rcu_sched_clock_irq+0x6ed/0x850 > [ 357.863084] [] ? __run_timers+0x42/0x260 > [ 357.868654] [] ? tick_setup_sched_timer+0x130/0x130 > [ 357.875182] [] update_process_times+0x7b/0x90 > [ 357.881188] [] tick_sched_timer+0x82/0xd0 > [ 357.886845] [] __run_hrtimer+0x81/0x200 > [ 357.892331] [] hrtimer_interrupt+0x192/0x450 > [ 357.898252] [] ? __do_softirq+0x2fa/0x33e > [ 357.903911] [] smp_apic_timer_interrupt+0xac/0x1d0 > [ 357.910349] [] apic_timer_interrupt+0x86/0x90 > [ 357.916347] > [ 357.918452] RIP: 0010:clflush_cache_range+0x3f/0x50 > [ 357.923324] RSP: 0018:ffff98529af89cc0 EFLAGS: 00000246 ORIG_RAX: ffff= ffffffffff12 > [ 357.930889] RAX: 0000000000000040 RBX: 0000000000038135 RCX: ffff98523= 3d36000 > [ 357.938013] RDX: ffff985233d36000 RSI: 0000000000001000 RDI: ffff98523= 3d35000 > [ 357.945145] RBP: ffff98529af89cc0 R08: 0000000000000001 R09: ffffb5753= fb23000 > [ 357.952271] R10: 000000000003fe00 R11: 0000000000000008 R12: 000000000= 0040000 > [ 357.959401] R13: ffff98525739ea40 R14: ffffb5753fb22000 R15: ffff98532= a58dd80 > [ 357.966536] [] svm_register_enc_region+0xd1/0x170 [= kvm_amd] > [ 357.973758] [] kvm_arch_vm_ioctl+0x84c/0xb00 > [ 357.979677] [] ? handle_mm_fault+0x6ff/0x1370 > [ 357.985683] [] kvm_vm_ioctl+0x69b/0x720 > [ 357.991167] [] do_vfs_ioctl+0x47d/0x680 > [ 357.996654] [] SyS_ioctl+0x68/0x90 > [ 358.001706] [] do_syscall_64+0x71/0x110 > [ 358.007192] [] entry_SYSCALL_64_after_hwframe+0x3d/= 0xa2 > > Tested by running a large 256gib SEV VM several times, saw no warnings. > Without the change warnings are seen. > > --- > arch/x86/kvm/svm/sev.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c > index 75fa6dd268f0..c2fe89ecdb2d 100644 > --- a/arch/x86/kvm/svm/sev.c > +++ b/arch/x86/kvm/svm/sev.c > @@ -465,6 +465,7 @@ static void sev_clflush_pages(struct page *pages[], u= nsigned long npages) > page_virtual =3D kmap_atomic(pages[i]); > clflush_cache_range(page_virtual, PAGE_SIZE); > kunmap_atomic(page_virtual); > + cond_resched(); If you add cond_resched() here, the frequency (once per 4K) might be too high. You may want to do it once per X pages, where X could be something like 1G/4K? > } > } > > -- > 2.35.1.1094.g7c7d902a7c-goog >