From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj1-f74.google.com (mail-pj1-f74.google.com [209.85.216.74]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0514F3FB040 for ; Fri, 29 May 2026 16:51:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.74 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780073496; cv=none; b=sWdNKQpR+dugjFLdM4OWyoOdW1wzjFhl/gNDur+Qx1N68eQtEJ0PDStoYibeVG/tLcDxyMN14ht/WcRcXn4WhfHajucK8Ukn9I6Y6UyFPlsZdij0div0J7RFtzrexWZThLSBLh1BaQR1znWCXXPL2tfOGn0oID4XF+iz+L/rgSM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780073496; c=relaxed/simple; bh=0lsKgKDWAG6ilUiGyVqdXWwZKr2qSgHhst802vkoXjo=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=PqMsm7EIaGy+BNMgZV0qckJVUTn3cwqBUTpW/yStpvoLJPq5ZC6qUIEFAprqKoTWAGR0Uc6L8MSTRM9LkdVt28Eu7PF5C7mixWND7JGpkIX0C4bKy0JkhWYQEa01Y709T3ePiJnZDHfZV0npKG/YDtfMp0N4rskns4XvpcMoc0o= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=R6Mq6zu6; arc=none smtp.client-ip=209.85.216.74 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="R6Mq6zu6" Received: by mail-pj1-f74.google.com with SMTP id 98e67ed59e1d1-36bc02d28b6so823596a91.3 for ; Fri, 29 May 2026 09:51:32 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1780073492; x=1780678292; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:from:to:cc:subject:date:message-id:reply-to; bh=yJlZ0p8w2Zt6JF+kmSoduaX7LUoYSExgSIwQfbW32Qc=; b=R6Mq6zu6p5QqeYVkcrUTTo+km9ImVC9ITKBZehmt7a52jmcR2dp3+ZJgPgYoca6uwp pPuTS1nKeBb3wZlzUogFBEPow5FjCJuO2QICnSv4aWhXWe+8pQBjpKLc9UlemKjmvrZR +R0Th4IHko+qlzkzhPrcoegVll7VFtNTUKEPMDnMCppqFg8Tdx5HqO/Bz6qYIM91I6TK w58OWYiKGscm7o3RHECSJqYQNbSt3GqSUET097XItDFTAlx7ronc9tqFXWZgJGnIX2bb Aw9ZUpgwQ4xaCzcLZqGEx/eepb1DCHYH+Ag7w4UZRe4aHlcUUwR0ejaw+Xyugjl4kkJd A9HA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1780073492; x=1780678292; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=yJlZ0p8w2Zt6JF+kmSoduaX7LUoYSExgSIwQfbW32Qc=; b=FkTg4SUFNvM/qg0+UNNhWd3ITaGcr9bLZ8+m6ofM/NIhHepgbX/fEOYtz4k3EYQfy8 PYrX8KkAv9k+PqX3dK8jOdaKhKirOvUoYHgQPlxtDw+kE5o3sr9H0aigMQc7+LDsLyxv Y8lalcy+WZnXXGQDynx6Ynq3Qttvr/YExo3UrYQbNMz45alRnOhF437ZfsqivhRQvL9m TZ8s4CvE7So9FpiFEPinGXKuPWkeDJjlsosnp0aBtzVoq+aGekk9N224SdieQLUulh2E jGC0qjETQHnxD7IdB8poDqa+tW3Bug2WnOAAxwuCS+9GL0gn26eJSDTeqGpzr870W/PS eVvQ== X-Forwarded-Encrypted: i=1; AFNElJ+EXUrNg3fXIU/sE5M6iQrU4ABmFu70wwaUtxo/VwWPxCXoUOna4yr40GCMXAMl7TOVTsOBPvUORD28PNo=@vger.kernel.org X-Gm-Message-State: AOJu0YyzcMm2DF1B8s6r/Iy64VlkP7FefV5WmOqMnX9aVzdOPO598IC2 J8c7h6uGCCC8MWMZjSGnn5NDo9VDc5/VuAyq5iseEvu9vRboaa/orFCFh3Jwi/JTMgWGKGxwq8C 6cd/kTg== X-Received: from pghk24.prod.google.com ([2002:a63:f018:0:b0:c82:3956:ab7c]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a20:ce4a:b0:3aa:f9cb:d438 with SMTP id adf61e73a8af0-3b427ecf1bcmr72868637.21.1780073491805; Fri, 29 May 2026 09:51:31 -0700 (PDT) Reply-To: Sean Christopherson Date: Fri, 29 May 2026 09:51:02 -0700 In-Reply-To: <20260529165114.748639-1-seanjc@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260529165114.748639-1-seanjc@google.com> X-Mailer: git-send-email 2.54.0.823.g6e5bcc1fc9-goog Message-ID: <20260529165114.748639-9-seanjc@google.com> Subject: [PATCH v2 08/20] KVM: x86/xen: Explicitly tag "shared info" page as never being dirty tracked From: Sean Christopherson To: Sean Christopherson , Paolo Bonzini , David Woodhouse , Paul Durrant , Peter Zijlstra , Ingo Molnar , Will Deacon , Boqun Feng Cc: Waiman Long , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, David Woodhouse , Sebastian Andrzej Siewior , syzbot+208f7f3e5f59c11aeb90@syzkaller.appspotmail.com, Carsten Stollmaier Content-Type: text/plain; charset="UTF-8" Explicitly mark the Xen shared info page as never being dirty tracked so that higher-level gpc APIs can be added to automatically take care of things like dirty tracking, without reintroducing the bug fixed by commit 55749769fe60 ("KVM: x86: Fix wall clock writes in Xen shared_info not to mark page dirty"). And because the code _looks_ buggy. No functional change intended. Signed-off-by: Sean Christopherson --- arch/x86/kvm/xen.c | 2 +- include/linux/kvm_host.h | 13 ++++++++++--- include/linux/kvm_types.h | 1 + virt/kvm/pfncache.c | 4 +++- 4 files changed, 15 insertions(+), 5 deletions(-) diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c index 020ef0ddab01..ab8e95647406 100644 --- a/arch/x86/kvm/xen.c +++ b/arch/x86/kvm/xen.c @@ -2334,7 +2334,7 @@ void kvm_xen_init_vm(struct kvm *kvm) { mutex_init(&kvm->arch.xen.xen_lock); idr_init(&kvm->arch.xen.evtchn_ports); - kvm_gpc_init(&kvm->arch.xen.shinfo_cache, kvm); + __kvm_gpc_init(&kvm->arch.xen.shinfo_cache, kvm, true); } void kvm_xen_destroy_vm(struct kvm *kvm) diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index 27498e990dff..0dc4eb78b6d9 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -1427,16 +1427,23 @@ int kvm_vcpu_write_guest(struct kvm_vcpu *vcpu, gpa_t gpa, const void *data, unsigned long len); /** - * kvm_gpc_init - initialize gfn_to_pfn_cache. + * __kvm_gpc_init - initialize gfn_to_pfn_cache. * * @gpc: struct gfn_to_pfn_cache object. * @kvm: pointer to kvm instance. + * @never_dirty: %true if the associated gfn should never be marked dirty * * This sets up a gfn_to_pfn_cache by initializing locks and assigning the * immutable attributes. Note, the cache must be zero-allocated (or zeroed by * the caller before init). */ -void kvm_gpc_init(struct gfn_to_pfn_cache *gpc, struct kvm *kvm); +void __kvm_gpc_init(struct gfn_to_pfn_cache *gpc, struct kvm *kvm, + bool never_dirty); + +static inline void kvm_gpc_init(struct gfn_to_pfn_cache *gpc, struct kvm *kvm) +{ + __kvm_gpc_init(gpc, kvm, false); +} /** * kvm_gpc_activate - prepare a cached kernel mapping and HPA for a given guest @@ -1942,7 +1949,7 @@ static inline void kvm_gpc_mark_dirty_in_slot(struct gfn_to_pfn_cache *gpc) { lockdep_assert_held(&gpc->lock); - if (!gpc->memslot) + if (!gpc->memslot || gpc->never_dirty) return; mark_page_dirty_in_slot(gpc->kvm, gpc->memslot, gpa_to_gfn(gpc->gpa)); diff --git a/include/linux/kvm_types.h b/include/linux/kvm_types.h index a568d8e6f4e8..e850adc3f47e 100644 --- a/include/linux/kvm_types.h +++ b/include/linux/kvm_types.h @@ -94,6 +94,7 @@ struct gfn_to_pfn_cache { kvm_pfn_t pfn; bool active; bool valid; + bool never_dirty; }; #ifdef KVM_ARCH_NR_OBJS_PER_MEMORY_CACHE diff --git a/virt/kvm/pfncache.c b/virt/kvm/pfncache.c index 70b102095173..9209f06c46b4 100644 --- a/virt/kvm/pfncache.c +++ b/virt/kvm/pfncache.c @@ -382,7 +382,8 @@ int kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, unsigned long len) return __kvm_gpc_refresh(gpc, gpc->gpa, uhva); } -void kvm_gpc_init(struct gfn_to_pfn_cache *gpc, struct kvm *kvm) +void __kvm_gpc_init(struct gfn_to_pfn_cache *gpc, struct kvm *kvm, + bool never_dirty) { rwlock_init(&gpc->lock); mutex_init(&gpc->refresh_lock); @@ -392,6 +393,7 @@ void kvm_gpc_init(struct gfn_to_pfn_cache *gpc, struct kvm *kvm) gpc->gpa = INVALID_GPA; gpc->uhva = KVM_HVA_ERR_BAD; gpc->active = gpc->valid = false; + gpc->never_dirty = never_dirty; } static int __kvm_gpc_activate(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long uhva, -- 2.54.0.823.g6e5bcc1fc9-goog