From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 7898D3D34AD for ; Mon, 20 Jul 2026 09:10:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784538629; cv=none; b=P/fr1HIowj3EMBx70RKOrl5iRrPO8eeILVXR4elHsF8G5ojBWRnck/pCGmqwNSY5J/TQ2OE3ZOYkmqqFwxhWqfXqbko7LsePPnxN0VvXo+yvdWiWL2KFJyPpKiMvmp6uvkY1LixfjP9CJrDxlJz+TEmzcbLYEPsU7Szbe9VhAB4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784538629; c=relaxed/simple; bh=UlymmXv5O50hqNpgc22rBOAaQC6RejWBv57yspEHDBs=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=ja50mLhhqxvGU3E96mIznUQeprElaEL4S4qoRk62/C/+WIEYUtm8JSyLsQ58j2mC5EbayEwnb/SxQ9afV7P7u4BAAClS60JnEq8O+5RF6yvGK9EvGtlhr9rEvCaycpWhj00I8bc9eTnXAetfw4ES37YkaiIepDSsQFc+VFRrSR0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=OJsRm18A; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="OJsRm18A" Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 95B242B; Mon, 20 Jul 2026 02:10:21 -0700 (PDT) Received: from [10.164.19.57] (unknown [10.164.19.57]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id AB0A63F86F; Mon, 20 Jul 2026 02:10:21 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1784538625; bh=UlymmXv5O50hqNpgc22rBOAaQC6RejWBv57yspEHDBs=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=OJsRm18AeNkXZJo3jbFuyTjOn5r8W3CeHjdK2jeME3loZaeVu6UivvZnY1ulkiEc6 jDMYcwEhD71Qsi81IIYGJ7Kc3HHSkPnbvAON+Sq3Ao8FFZQMitITksOkMe8kYfo0TV 3TsrCcuWVZ4vvGfo+Rc+VM2SiUBMfceWulUh8o6A= Message-ID: <4a598a6c-496f-441c-b268-a725f9ee8090@arm.com> Date: Mon, 20 Jul 2026 14:40:18 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] KVM: arm64: ptdump: Flush the last region To: Marc Zyngier Cc: Wei-Lin Chang , linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-kernel@vger.kernel.org, Oliver Upton , Fuad Tabba , Joey Gouly , Steffen Eiden , Suzuki K Poulose , Zenghui Yu , Catalin Marinas , Will Deacon , Ryan Roberts , Sebastian Ene , Vincent Donnefort References: <20260717231233.2299068-1-weilin.chang@arm.com> <868q76f2wy.wl-maz@kernel.org> Content-Language: en-US From: Dev Jain In-Reply-To: <868q76f2wy.wl-maz@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 20/07/26 2:33 pm, Marc Zyngier wrote: > On Mon, 20 Jul 2026 09:53:29 +0100, > Dev Jain wrote: >> >> >> >> On 18/07/26 4:42 am, Wei-Lin Chang wrote: >>> Currently the stage-2 ptdump calls note_page() at each leaf entry visit. >>> This simply misses the output of the last region, because note_page() >>> only dumps output when it detects a change in level/prot, or when the >>> walk enters a next marker section. The last region in the guest IPA >>> space with the same level/prot is not dumped since there is no change >>> after it. >>> >>> To dump the final region, manually issue a note_page() call with address >>> BIT(ia_bits) (end of guest IPA space) and level == -1 to trigger a level >>> change after the last region. Additionally treat level == -1 as a last >>> flushing note_page() call and avoid dumping the name of the next marker >>> for this case. >>> >>> Fixes: 7c4f73548ed1 ("KVM: arm64: Register ptdump with debugfs on guest creation") >>> Reported-by: Sashiko AI >>> Closes: https://lore.kernel.org/kvmarm/20260630122758.891011F00A3A@smtp.kernel.org/ >>> Signed-off-by: Wei-Lin Chang >>> --- >>> arch/arm64/kvm/ptdump.c | 8 +++++--- >>> arch/arm64/mm/ptdump.c | 5 +++-- >>> 2 files changed, 8 insertions(+), 5 deletions(-) >>> >>> diff --git a/arch/arm64/kvm/ptdump.c b/arch/arm64/kvm/ptdump.c >>> index c9140e22abcf..4096e4a92fae 100644 >>> --- a/arch/arm64/kvm/ptdump.c >>> +++ b/arch/arm64/kvm/ptdump.c >>> @@ -155,11 +155,13 @@ static int kvm_ptdump_guest_show(struct seq_file *m, void *unused) >>> .seq = m, >>> }; >>> >>> - write_lock(&kvm->mmu_lock); >>> + guard(write_lock)(&kvm->mmu_lock); >> >> The guard clause change has nothing to do with the fix I think? Although the change >> is small and the fix is for a recent commit so maybe we don't care having this >> in the same patch - not sure how strict kvm reviewers are about this : ) >> > > Look at the quality spaghetti code this would otherwise result in: > > write_lock(); > ret = kvm_pgtable_walk(); > if (ret) { > write_unlock(); > return ret; > } > note_page_flush(); > write_unlock(); > > return 0; > > How is that better? So it has *everything* to do with the fix. > > And FWIW, the policy for KVM is that we don't do lock->guard > conversions as a separate patches. Only when we need to change the > code, and as part of the patch that changes that code. Which is > exactly what is happening here. I agree, thanks. > >> >>> ret = kvm_pgtable_walk(mmu->pgt, 0, BIT(mmu->pgt->ia_bits), &walker); >>> - write_unlock(&kvm->mmu_lock); >>> + if (ret) >>> + return ret; >>> + note_page(&st->parser_state.ptdump, BIT(mmu->pgt->ia_bits), -1, 0); >>> >>> - return ret; >>> + return 0; >>> } >>> >>> static int kvm_ptdump_guest_open(struct inode *m, struct file *file) >>> diff --git a/arch/arm64/mm/ptdump.c b/arch/arm64/mm/ptdump.c >>> index ab9899ca1e5f..fed4e4407e0e 100644 >>> --- a/arch/arm64/mm/ptdump.c >>> +++ b/arch/arm64/mm/ptdump.c >>> @@ -194,6 +194,7 @@ void note_page(struct ptdump_state *pt_st, unsigned long addr, int level, >>> struct ptdump_pg_state *st = container_of(pt_st, struct ptdump_pg_state, ptdump); >>> struct ptdump_pg_level *pg_level = st->pg_level; >>> static const char units[] = "KMGTPE"; >>> + bool flush = level == -1; >> >> Can we do something similar to what S1 ptdump does (note_page_flush in ptdump_walk_pgd). > > See Mark's email. > > M. >