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 AA58DECAAD4 for ; Wed, 31 Aug 2022 18:43:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232837AbiHaSnU (ORCPT ); Wed, 31 Aug 2022 14:43:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43328 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232482AbiHaSnB (ORCPT ); Wed, 31 Aug 2022 14:43:01 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1F0552622 for ; Wed, 31 Aug 2022 11:42:15 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1661971334; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=bSO3yGBv6o2ftJ8n+2sbUGawaPifKr8wIkuEWc2hHFA=; b=RRHjWndGeGb8fSf/ujOjYJncqkX6Wd7Uyg3tM0+4I2vjoTM9srmosuiHJqaiooNWWr+rFD WT3huulLL16fYJez9+0i4lGYRZ59FU7eEimer2I1vrtIVaSY6z6MGzIUFUchHrxSZt5ee9 0SUqBepcxBj+xVJIrB9w8XudAZi8I8s= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-587-y70-O1cSN32KWCKrvfc_iA-1; Wed, 31 Aug 2022 14:42:12 -0400 X-MC-Unique: y70-O1cSN32KWCKrvfc_iA-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 6BFAD3810D21; Wed, 31 Aug 2022 18:42:12 +0000 (UTC) Received: from starship (unknown [10.40.194.96]) by smtp.corp.redhat.com (Postfix) with ESMTP id C9F72945D2; Wed, 31 Aug 2022 18:42:10 +0000 (UTC) Message-ID: <9c3e126bdee38bc4a0fa03eec994878aca4f3b3e.camel@redhat.com> Subject: Re: [PATCH 16/19] KVM: x86: Explicitly track all possibilities for APIC map's logical modes From: Maxim Levitsky To: Sean Christopherson , Paolo Bonzini Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Suravee Suthikulpanit , Li RongQing Date: Wed, 31 Aug 2022 21:42:09 +0300 In-Reply-To: <20220831003506.4117148-17-seanjc@google.com> References: <20220831003506.4117148-1-seanjc@google.com> <20220831003506.4117148-17-seanjc@google.com> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.36.5 (3.36.5-2.fc32) MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.11.54.5 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2022-08-31 at 00:35 +0000, Sean Christopherson wrote: > Track all possibilities for the optimized APIC map's logical modes > instead of overloading the pseudo-bitmap and treating any "unknown" value > as "invalid". > > As documented by the now-stale comment above the mode values, the values > did have meaning when the optimized map was originally added. That > dependent logical was removed by commit e45115b62f9a ("KVM: x86: use > physical LAPIC array for logical x2APIC"), but the obfuscated behavior > and its comment were left behind. > > Opportunistically rename "mode" to "logical_mode", partly to make it > clear that the "disabled" case applies only to the logical map, but also > to prove that there is no lurking code that expects "mode" to be a bitmap. > > Functionally, this is a glorified nop. > > Signed-off-by: Sean Christopherson > --- > arch/x86/include/asm/kvm_host.h | 21 ++++++++++-------- > arch/x86/kvm/lapic.c | 38 ++++++++++++++++++++++++--------- > 2 files changed, 40 insertions(+), 19 deletions(-) > > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h > index 1f51411f3112..0184e64ab555 100644 > --- a/arch/x86/include/asm/kvm_host.h > +++ b/arch/x86/include/asm/kvm_host.h > @@ -955,19 +955,22 @@ struct kvm_arch_memory_slot { > }; > > /* > - * We use as the mode the number of bits allocated in the LDR for the > - * logical processor ID. It happens that these are all powers of two. > - * This makes it is very easy to detect cases where the APICs are > - * configured for multiple modes; in that case, we cannot use the map and > - * hence cannot use kvm_irq_delivery_to_apic_fast either. > + * Track the mode of the optimized logical map, as the rules for decoding the > + * destination vary per mode. Enabling the optimized logical map requires all > + * software-enabled local APIs to be in the same mode, each addressable APIC to > + * be mapped to only one MDA, and each MDA to map to at most one APIC. > */ > -#define KVM_APIC_MODE_XAPIC_CLUSTER 4 > -#define KVM_APIC_MODE_XAPIC_FLAT 8 > -#define KVM_APIC_MODE_X2APIC 16 > +enum kvm_apic_logical_mode { > + KVM_APIC_MODE_SW_DISABLED, > + KVM_APIC_MODE_XAPIC_CLUSTER, > + KVM_APIC_MODE_XAPIC_FLAT, > + KVM_APIC_MODE_X2APIC, > + KVM_APIC_MODE_MAP_DISABLED, > +}; > > struct kvm_apic_map { > struct rcu_head rcu; > - u8 mode; > + enum kvm_apic_logical_mode logical_mode; > u32 max_apic_id; > union { > struct kvm_lapic *xapic_flat_map[8]; > diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c > index 8209caffe3ab..3b6ef36b3963 100644 > --- a/arch/x86/kvm/lapic.c > +++ b/arch/x86/kvm/lapic.c > @@ -168,7 +168,12 @@ static bool kvm_use_posted_timer_interrupt(struct kvm_vcpu *vcpu) > > static inline bool kvm_apic_map_get_logical_dest(struct kvm_apic_map *map, > u32 dest_id, struct kvm_lapic ***cluster, u16 *mask) { > - switch (map->mode) { > + switch (map->logical_mode) { > + case KVM_APIC_MODE_SW_DISABLED: > + /* Arbitrarily use the flat map so that @cluster isn't NULL. */ > + *cluster = map->xapic_flat_map; > + *mask = 0; > + return true; > case KVM_APIC_MODE_X2APIC: { > u32 offset = (dest_id >> 16) * 16; > u32 max_apic_id = map->max_apic_id; > @@ -193,8 +198,10 @@ static inline bool kvm_apic_map_get_logical_dest(struct kvm_apic_map *map, > *cluster = map->xapic_cluster_map[(dest_id >> 4) & 0xf]; > *mask = dest_id & 0xf; > return true; > + case KVM_APIC_MODE_MAP_DISABLED: > + return false; > default: > - /* Not optimized. */ > + WARN_ON_ONCE(1); BTW unless I am mistaken, this warning is guest triggerable, and thus as you say when 'panic_on_warn=1', this will panic the host kernel. Best regards, Maxim Levitsky > return false; > } > } > @@ -256,10 +263,12 @@ void kvm_recalculate_apic_map(struct kvm *kvm) > goto out; > > new->max_apic_id = max_id; > + new->logical_mode = KVM_APIC_MODE_SW_DISABLED; > > kvm_for_each_vcpu(i, vcpu, kvm) { > struct kvm_lapic *apic = vcpu->arch.apic; > struct kvm_lapic **cluster; > + enum kvm_apic_logical_mode logical_mode; > u32 x2apic_id, physical_id; > u16 mask; > u32 ldr; > @@ -314,7 +323,8 @@ void kvm_recalculate_apic_map(struct kvm *kvm) > new->phys_map[physical_id] = apic; > } > > - if (!kvm_apic_sw_enabled(apic)) > + if (new->logical_mode == KVM_APIC_MODE_MAP_DISABLED || > + !kvm_apic_sw_enabled(apic)) > continue; > > ldr = kvm_lapic_get_reg(apic, APIC_LDR); > @@ -322,25 +332,33 @@ void kvm_recalculate_apic_map(struct kvm *kvm) > continue; > > if (apic_x2apic_mode(apic)) { > - new->mode |= KVM_APIC_MODE_X2APIC; > + logical_mode = KVM_APIC_MODE_X2APIC; > } else { > ldr = GET_APIC_LOGICAL_ID(ldr); > if (kvm_lapic_get_reg(apic, APIC_DFR) == APIC_DFR_FLAT) > - new->mode |= KVM_APIC_MODE_XAPIC_FLAT; > + logical_mode = KVM_APIC_MODE_XAPIC_FLAT; > else > - new->mode |= KVM_APIC_MODE_XAPIC_CLUSTER; > + logical_mode = KVM_APIC_MODE_XAPIC_CLUSTER; > } > + if (new->logical_mode != KVM_APIC_MODE_SW_DISABLED && > + new->logical_mode != logical_mode) { > + new->logical_mode = KVM_APIC_MODE_MAP_DISABLED; > + continue; > + } > + new->logical_mode = logical_mode; > > - if (!kvm_apic_map_get_logical_dest(new, ldr, &cluster, &mask)) > + if (WARN_ON_ONCE(!kvm_apic_map_get_logical_dest(new, ldr, > + &cluster, &mask))) { > + new->logical_mode = KVM_APIC_MODE_MAP_DISABLED; > continue; > + } > > if (!mask) > continue; > > ldr = ffs(mask) - 1; > if (!is_power_of_2(mask) || cluster[ldr]) { > - new->mode = KVM_APIC_MODE_XAPIC_FLAT | > - KVM_APIC_MODE_XAPIC_CLUSTER; > + new->logical_mode = KVM_APIC_MODE_MAP_DISABLED; > continue; > } > cluster[ldr] = apic; > @@ -993,7 +1011,7 @@ static bool kvm_apic_is_broadcast_dest(struct kvm *kvm, struct kvm_lapic **src, > { > if (kvm->arch.x2apic_broadcast_quirk_disabled) { > if ((irq->dest_id == APIC_BROADCAST && > - map->mode != KVM_APIC_MODE_X2APIC)) > + map->logical_mode != KVM_APIC_MODE_X2APIC)) > return true; > if (irq->dest_id == X2APIC_BROADCAST) > return true;