From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 CE1D24F8B1 for ; Mon, 8 Apr 2024 07:41:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1712562114; cv=none; b=jh6p5bokOkpIZTfqRv+pOTBMxZwDBZ/86ka3HUN0C8Bf4AYODL7x61YrkiJuL0KxoANwtEOz+XTK+0iqNs/0cjjsZyGz1mT3oKUyMKzjmNUz0HnjmmCp8mdn9Hpg1kMOd41LJ37MXUg4v3I682PBPuAGmpLtP82UQl83I8b0BXk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1712562114; c=relaxed/simple; bh=ERdr/5qhocvZ1CEaB6/iZw2BZjhNKUNS8UqnDQHfFtA=; h=Date:Message-ID:From:To:Cc:Subject:In-Reply-To:References: MIME-Version:Content-Type; b=XBicrbZPZ1lXjxAt4WOjlqttgue4XzCoSHvxi3Db/N5x1MPE6BxJGIrcdBoM/bZbsGF0jGwZA3SRnWWwqPmpHLziMI1i+QNd5+BZ1vD6zMdyG0mXBRFaqdcoH3QMbD1kIcNQSXYCv8jydFm51rsNDbyV4/3T/enYsOSKbcWa0gU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Uc0H6a1S; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Uc0H6a1S" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4ADCBC433F1; Mon, 8 Apr 2024 07:41:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1712562114; bh=ERdr/5qhocvZ1CEaB6/iZw2BZjhNKUNS8UqnDQHfFtA=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=Uc0H6a1SfuMp7NZHPa91soI37aXhABAuxpdYAEHGdNWiwwvq0j43D0hV+RirXiUIz +N8vQ1IkyVZLQynq+Lpm20ACwp5RqsNnFYxzi12AtZt7GqslNZ2VKWMRjWJ7/bhXI/ uSV0NnA/9lMyZqSMOFBUIgpAnbdD7MEgJTOMImo5KGW27LrQKv9u/UPATWqUBbWwLT mBLa2Dwqwn+e5sm9Gh9OntKkVOWWXDKzm1ai6mTCj8JOqzPwFYrcF4q1drTh9Japo/ mkYaeYTfmB4dUHp1PfTDoN3LJJJJV+QTbiEA5738HQLkLcQXEy9LQmudvrtcPkt1ja Tl2lwmMZjYeig== Received: from sofa.misterjones.org ([185.219.108.64] helo=goblin-girl.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.95) (envelope-from ) id 1rtjdX-002OcU-Vd; Mon, 08 Apr 2024 08:41:52 +0100 Date: Mon, 08 Apr 2024 08:41:50 +0100 Message-ID: <864jccti69.wl-maz@kernel.org> From: Marc Zyngier To: Fuad Tabba Cc: kvmarm@lists.linux.dev, will@kernel.org, qperret@google.com, seanjc@google.com, alexandru.elisei@arm.com, catalin.marinas@arm.com, philmd@linaro.org, james.morse@arm.com, suzuki.poulose@arm.com, oliver.upton@linux.dev, mark.rutland@arm.com, broonie@kernel.org, joey.gouly@arm.com, rananta@google.com Subject: Re: [PATCH v1 03/44] KVM: arm64: Move setting the page as dirty out of the critical section In-Reply-To: <20240327173531.1379685-4-tabba@google.com> References: <20240327173531.1379685-1-tabba@google.com> <20240327173531.1379685-4-tabba@google.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/29.2 (aarch64-unknown-linux-gnu) MULE/6.0 (HANACHIRUSATO) Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: tabba@google.com, kvmarm@lists.linux.dev, will@kernel.org, qperret@google.com, seanjc@google.com, alexandru.elisei@arm.com, catalin.marinas@arm.com, philmd@linaro.org, james.morse@arm.com, suzuki.poulose@arm.com, oliver.upton@linux.dev, mark.rutland@arm.com, broonie@kernel.org, joey.gouly@arm.com, rananta@google.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false On Wed, 27 Mar 2024 17:34:50 +0000, Fuad Tabba wrote: > > Move the unlock earlier in user_mem_abort() to shorten the > critical section. This also helps for future refactoring and > reuse of similar code. > > Signed-off-by: Fuad Tabba > --- > arch/arm64/kvm/mmu.c | 8 +++++--- > 1 file changed, 5 insertions(+), 3 deletions(-) > > diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c > index 18680771cdb0..3afc42d8833e 100644 > --- a/arch/arm64/kvm/mmu.c > +++ b/arch/arm64/kvm/mmu.c > @@ -1522,8 +1522,10 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, > > read_lock(&kvm->mmu_lock); > pgt = vcpu->arch.hw_mmu->pgt; > - if (mmu_invalidate_retry(kvm, mmu_seq)) > + if (mmu_invalidate_retry(kvm, mmu_seq)) { > + ret = -EAGAIN; > goto out_unlock; > + } > > /* > * If we are not forced to use page mapping, check if we are > @@ -1581,6 +1583,8 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, > memcache, > KVM_PGTABLE_WALK_HANDLE_FAULT | > KVM_PGTABLE_WALK_SHARED); > +out_unlock: > + read_unlock(&kvm->mmu_lock); > > /* Mark the page dirty only if the fault is handled successfully */ > if (writable && !ret) { > @@ -1588,8 +1592,6 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, > mark_page_dirty_in_slot(kvm, memslot, gfn); > } > > -out_unlock: > - read_unlock(&kvm->mmu_lock); > kvm_release_pfn_clean(pfn); > return ret != -EAGAIN ? ret : 0; > } It now means that things such as marking a page dirty happens outside of the lock, which may interact with the dirty log/bitmap stuff. Can you elaborate on *why* this is correct? Thanks, M. -- Without deviation from the norm, progress is not possible.