From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BE053606A941 for ; Tue, 3 Nov 2026 08:48:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=lists.infradead.org header.i=@lists.infradead.org header.a=rsa-sha256 header.s=bombadil.20210309 header.b=ZmJx9b+n; dkim=pass (1024-bit key, unprotected) header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256 header.s=key1 header.b=aZ/qKBhl DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From: Reply-To:Content-Type:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Unsubscribe-Post: List-Owner; bh=XtJiRyro5pp1Ubk31vh+uEkbIHM0qppKB9W3IOPNN0E=; b=ZmJx9b+nn9GqBU uSUv6oHcQPYRkdRvQUt6SaQCn19ZwcScisZwHoEIft+88syWQyO0E2xv+swEOqPgSsDQ/vk5T7GdD gdXgi4rAkqlhiwI4mb8vjlLVZnRagAkp5ox/xer8Dp9FxpGpLYAlDkFj2b8ZWHHPre3qD+meWQ7T7 m9/cyDewmeF9usukMEghwXXCn+ZHBaDcb1S7yibZxMKtbHpklb0fFDeZ1jJSEc0h13wLRekP++3cx LcmtmKIKFxaj4k3EHpz+Qlzp1rBLl6sYuW20oAkq4Vpl54Cyx98PI6F/DcyY/cEaFH6YOZsiXvGqb +EuFNlSFmtghYVRWEgPQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.100.1 #2 (Red Hat Linux)) id 1xOABL-00000001cvv-3Sln; Tue, 03 Nov 2026 08:47:51 +0000 Received: from out-95.mta1.migadu.com ([95.215.58.95] helo=mta1.migadu.com) by bombadil.infradead.org with esmtps (Exim 4.100.1 #2 (Red Hat Linux)) id 1xOABH-00000001csJ-3olY for linux-arm-kernel@lists.infradead.org; Tue, 03 Nov 2026 08:47:50 +0000 X-Envelope-To: linux-arm-kernel@lists.infradead.org DKIM-Signature: a=rsa-sha256; bh=vxgqiZ0okcZF28/Y6ng3hoY+gPOQ7Ju8Td5h/EbU8As=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1793695663; v=1; x=1794300463; b=aZ/qKBhlKEc2WXQLYiCL3Yy8XT146ylvR7IJx0CfEBuBYqUSNrxd51Y1kNTNkFqLB+dEug7G GdeizSkTbDL/1Uir2Qv+3/UnT/7NUSUiKeMUifbYjyK4dUGWycHEfs1k3Y4r40S9/l9OHOcFH9D n8N6xmgJo2YzgOI46a4gbYDM= X-Envelope-To: linux-arm-kernel@lists.infradead.org Received: by smtp.migadu.com with ESMTPS id d3cf5bf9ecc66116; Tue, 03 Nov 2026 08:47:43 +0000 X-Mizu-Trace-ID: d3cf5bf9ecc66116 X-Migadu-Flow: FLOW_OUT From: Fuad Tabba To: Marc Zyngier , Oliver Upton Cc: 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: [PATCH 2/3] KVM: arm64: Skip empty IPA ranges when destroying stage-2 page-tables Date: Tue, 3 Nov 2026 08:47:41 +0000 Message-ID: <20261103084742.1302597-3-fuad.tabba@linux.dev> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20261103084742.1302597-1-fuad.tabba@linux.dev> References: <20261103084742.1302597-1-fuad.tabba@linux.dev> X-Archived-By: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20261103_004748_098920_199E6810 X-CRM114-Status: GOOD ( 11.74 ) X-Spam-Score: -2.1 (--) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" X-Spam-Status: No, score=-18.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=4.0.1 X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 The page-table walker steps over an empty entry in one go, but kvm_stage2_destroy() starts a new walk for every block-sized chunk of the IPA space. Tearing down a VM that requests a 52-bit IPA then takes 2^27 walks with 16K pages (2^22 with 4K), however little it maps. crosvm requests the host's limit. After destroying each chunk, look up the entry at its start and, if it is empty and larger than a chunk, skip its whole range. The lookup reads fields that hold the mapping tree on a pKVM stage-2, so this depends on the previous patch keeping pKVM out of stage2_destroy_range(). For the same reason, call kvm_pgtable_stage2_destroy_range() directly rather than through KVM_PGT_FN(). Fixes: 4ddfab5436b69 ("KVM: arm64: Reschedule as needed when destroying the stage-2 page-tables") Signed-off-by: Fuad Tabba --- arch/arm64/kvm/mmu.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c index 42977cf8a7f5d..10b425a0141be 100644 --- a/arch/arm64/kvm/mmu.c +++ b/arch/arm64/kvm/mmu.c @@ -1010,9 +1010,20 @@ static void stage2_destroy_range(struct kvm_pgtable *pgt, phys_addr_t addr, u64 next; do { + kvm_pte_t pte; + s8 level; + next = stage2_range_addr_end(addr, end); - KVM_PGT_FN(kvm_pgtable_stage2_destroy_range)(pgt, addr, - next - addr); + kvm_pgtable_stage2_destroy_range(pgt, addr, next - addr); + + /* + * The walk freed every table it emptied, so skipping an empty + * entry here doesn't leave anything behind. + */ + if (!kvm_pgtable_get_leaf(pgt, addr, &pte, &level, 0) && !pte && + level < KVM_PGTABLE_MIN_BLOCK_LEVEL) + next = __stage2_range_addr_end(addr, end, kvm_granule_size(level)); + if (next != end) cond_resched(); } while (addr = next, addr != end); -- 2.47.3