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=1793724496; b=jfMlxZUkLhyhja2Ec8ujQX5YPvojZ96IXR/UlwTjjmewf9aS8c0P48aK1M3EMWYMKlOu bYnjhkCEXi+C0upcn89fBnVAqM6tfRLhPucmVnMYf07NLDqoVJJLKz1UVP/ZWB2Hnph0Q o3mdjDjJbwPYKP8v/d1UQNqtqslzLowOjinvOMwRdwoQHAKMvq1EMX0ZBfCyuZXPezfux j6QBzaNRgy50bsEZjwWqUHgOgM5OM49J643g78W6a4aLRI6933wIZBdDxUsDXDMoHbzQW J8ZNnAowUXuJ0/cgJ+1TtcwS0vGIgvlG0fm7WLeF/QSN8/Ve4dToHkkmxqqwzzF5M5g== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793724496; h=Received:DKIM-Signature:Date:From:To:Cc:Subject:Message-ID: References:MIME-Version:Content-Type:Content-Disposition:In-Reply-To; bh=l2PUnbLRvVKCeeWmqzWIWxHl8MNmgKSAW2Fw91nyKLI=; b=giA3+dDMYMO25CttH0BHI2MvFe97jCaVqeDSF5fMEbQ14i/Qn7uhlVIrtZOXGliG4iPi BsheqaMqVjkN56S7evpB6YDuBG+8kqq0dfU+7Y860f9Y70q6iQfvOcTzY6nFT0VMfL/Pd ac8uvfTt4YYgrb7/KqGORxl05aPA+wHRM9RUH3aa2q3azKSNpFcbG7HCQwZMRM6f6aAVo KeRrUhrvt3u2WikvL6bd166UaHRI1pp+dpMnKglUDN75fh8VGjiGSJ+04G5j0x/HYgAjC 3qzV1UgNBpzGxz8V01ljaWLFs0AhJAsHISS24JFMVw9bAls8odH+ZiyNI+8JCLabF4Q== 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=FgrZ2i1+; 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 7CAD8606A328; Tue, 3 Nov 2026 16:48:16 +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=FgrZ2i1+ Received: by smtp.kernel.org (Postfix) with ESMTPSA id C5E1E1F000C1; Tue, 3 Nov 2026 16:48:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793724496; bh=l2PUnbLRvVKCeeWmqzWIWxHl8MNmgKSAW2Fw91nyKLI=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=FgrZ2i1+J+WK+vodFp2ovSXNFdwdlFJaTFd8IMGA6W1WY6waPIpnLf7ufNTEC5hqU pRIK76PgnaLTk/aitEW7yHQbPu9xAsxKKt1mmN2CqhGoYmSRMaDMJLdfPZxr2bHhvT rlJ2EEhaF4PoByjkBunCVYXLEDlM0L8aevI9cpzk6l+8kgW9C4zcpxOkx7fyEfmEuO 0mQSjVoo40D+Z/pFif/QqQJ+FUiKOrX0rdH65WhkSvsA0ejBMe+ne7xTQxbp+GZxyB hz9erxg30S1taUiUvNlfgJ3+4CN7VXZNhCRrYsDFYf+vE7OrGnE6YJlHVSZhf6rfo5 su0cUG62lpQDg== Date: Tue, 3 Nov 2026 08:48:14 -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 08:47:31AM -0800, Oliver Upton wrote: > 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. Next patch heh :)