From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793724453; b=brCbQqydGWp0fODYa5KCG+OhZ0Dcpmxq38mJpDBm422QsgBUogyfINwCV/ZEWKMY/QNs 5Aw+kJJ7Q2FF627lSdODwNDu12odMEoIxH9tL5XB+osNKkZUmtQxqQFLy33x6PLpYJvo6 CfyH+Go40lZalVO7hbYsj9Qu3h/BdncGvMY8rTW/vmsUwMtPcaEIuQpJIHUnSFYdZ2O37 Vob5axGsYcjC2Kecf2onBOW0dHWzUWvonGD6JMSADh0T9blhXBeMKQGLsQ4VAENrbrubv WERI33g1JW2Uml+RB1caZfZsDOLLTsr1yoKRMsmMszVQr2bhZJA1iQQGYO1/aaUJdHw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793724453; h=Received:DKIM-Signature:Date:From:To:Cc:Subject:Message-ID: References:MIME-Version:Content-Type:Content-Disposition:In-Reply-To; bh=Q/ltEAc+N+3ENVziqnPe9OWDAKNpP/rCTARs1hVfB1Y=; b=AF96scrZ6qXz9SmNfHi4WWLr70hx41trYg6h7iFIGI0X+cShFurfrM9YRVQCmo+BCkQA 7SjOCOkCyoKxnhI8NHG+n9aPmHKB3aEhUwZpxc9r0oI3ToWQ7etsuAaIaFp1H5RoITiKo MxxzmSbCozUYA5Z++nh5u/tet3YCwkZpNLiRATsPiG1yVkgZYjvB/Xfvt8jDC8qqYjY/9 1c5QmggJsoLjref2r1fnzRhCf5VNNiicWv3D9kZ4144ONWviq9nnnFb/3CP1LTLpfY+Qg Ufwunzqd4aYHPL6Oi6NOV0nph6PqlP5H1OqRZULqkX9nCokSPAm+40WEb4/X95FelWw== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=EH1UgyGW; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 22D22606A329; Tue, 3 Nov 2026 16:47:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=EH1UgyGW Received: by smtp.kernel.org (Postfix) with ESMTPSA id 769DE1F00919; Tue, 3 Nov 2026 16:47:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793724452; bh=Q/ltEAc+N+3ENVziqnPe9OWDAKNpP/rCTARs1hVfB1Y=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=EH1UgyGWR3BQgaGa2fY0FrvPhw0YrCxuvKsWxRS4qOVEE4xwX1BtTABDzgitcwH+F d5TpvMRv/iEnKwkiN8ZLZmfJYjxsGa1608mwytH5s/dLdvYGanDtHoo3M1ED4+/VhZ SJHH4ERCS/OlaC7IIpraTBgPsU8zulVrWGbln8CXqudG5U0b+dhq2SfVagd4AX7Rg1 AAqTWlmMKLtqFfq7aaogICoZSaDCZrpGieBzKIwhQpcSsC9mSnJlZhGhEYPmBc4gl0 OHTJs4XktOIdB128KA3U5V0c/ueV//1psyTDDiWxzrSjVBNkBgBSYSAnJMTdwSUSgM /M/3kNXS6w+Qg== Date: Tue, 3 Nov 2026 08:47:31 -0800 From: Oliver Upton To: Vincent Donnefort Cc: Fuad Tabba , Marc Zyngier , kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Joey Gouly , Steffen Eiden , Suzuki K Poulose , Zenghui Yu , Catalin Marinas , Will Deacon , Mark Rutland , Raghavendra Rao Ananta , Fuad Tabba Subject: Re: [PATCH 1/3] KVM: arm64: Don't walk the whole IPA space when destroying a pKVM stage-2 Message-ID: References: <20261103084742.1302597-1-fuad.tabba@linux.dev> <20261103084742.1302597-2-fuad.tabba@linux.dev> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Tue, Nov 03, 2026 at 04:37:54PM +0000, Vincent Donnefort wrote: > > @@ -513,10 +514,18 @@ void pkvm_pgtable_stage2_destroy_range(struct kvm_pgtable *pgt, > > kvm->arch.pkvm.is_dying = true; > > } > > > > - if (kvm_vm_is_protected(kvm)) > > - __pkvm_pgtable_stage2_reclaim(pgt, addr, addr + size); > > - else > > - __pkvm_pgtable_stage2_unshare(pgt, addr, addr + size); > > + /* Called once for the whole IPA space, so reschedule between mappings */ > > + for_each_mapping_in_range_safe(pgt, addr, addr + size, mapping) { > > + u64 start = __pkvm_mapping_start(mapping); > > + u64 end = __pkvm_mapping_end(mapping) + 1; > > + > > + if (kvm_vm_is_protected(kvm)) > > + __pkvm_pgtable_stage2_reclaim(pgt, start, end); > > + else > > + __pkvm_pgtable_stage2_unshare(pgt, start, end); > > + > > + cond_resched(); > > + } > > } > > Just thought that it is a bit weird that pkvm_pgtable_stage2_destroy_range() > does cond_resched() while kvm_pgtable_stage2_destroy_range() does not. > > How about instead kvm_stage2_destroy() refines start/end with some accessors > calling in pkvm.c pkvm_mapping_iter_first() / pkvm_mapping_iter_last()? Yeah, I'd rather we tackle this as a general problem than doing some pKVM specific hacks. Seems to me that we do a lot of wasted work even in the non-pKVM case where the outer loop will continue to iterate KVM_PGTABLE_MIN_BLOCK_LEVEL worth of IPA even if the underlying table is empty. What we'd want is for the kvm_pgtable_stage2_destroy_range() implementation to report back how much of the IPA space it actually iterated over. We wouldn't want to keep re-visiting the same invalid PGD entry only because it's larger than our max block size. Thanks, Oliver