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 08DD0606D834 for ; Fri, 6 Nov 2026 12:02:46 +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=fIvKORtt; dkim=pass (1024-bit key, unprotected) header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256 header.s=key1 header.b=rRn/ijYe 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=O8RkL6vjgz7s3PYbOIeBih+CTzkMDKhpUQb62pbipoc=; b=fIvKORttl50j3Y 7cE05AeZaVp/joNeLhoFpDMSzKrQWsfDqQGdtbPL4zDv/P7s2eZrQwd/wvB1OQJ48An6ZvFQ5FRsq S549aJ63NI255LTWMSbSgcTStOqXaF7MeYBxFvrrTHitOedZZBtoCdUPdnr4kuCIbbyQbHSBobyKB 6hKmYv3fH5YrkPV703nBRCidJ5X3eedUpWJG8Y85Ey5dCVW1i4vUJwqsjcYkS5U5A2Sf3RfLyIKUZ diuLp+ZxYSaroGH0cpin83B5Z8WpzVj082HFAf4m5zDz4AOfpWwsu0jR+AFjkzDAtxz/X+Lid7e1A iP/zV9dN4cYpsRYqHFbQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.100.1 #2 (Red Hat Linux)) id 1xPIeW-0000000CFOv-05KZ; Fri, 06 Nov 2026 12:02:40 +0000 Received: from out-14.mta0.migadu.com ([2001:41d0:1004:224b::e] helo=mta0.migadu.com) by bombadil.infradead.org with esmtps (Exim 4.100.1 #2 (Red Hat Linux)) id 1xPIeT-0000000CFMy-2mVY for linux-arm-kernel@lists.infradead.org; Fri, 06 Nov 2026 12:02:38 +0000 X-Envelope-To: linux-arm-kernel@lists.infradead.org DKIM-Signature: a=rsa-sha256; bh=yNefybntTG1L/O8byYfqw9hjpQSNkaHxLxwAmXPvo5I=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1793966555; v=1; x=1794571355; b=rRn/ijYeof31L17BBvUIqQ9rbsyPv42zcI1vz8cUu7CveTCLbsnCVzkUy/OM2OGxBYGlcl1s 94jDEKAKDK6fxwuTz86sjZ5vngbBnNSGKvN/iFitbMbRakivL6+fbxF3iwW8Sf1tCfTRITu+FWY JmrTiEy8DPVJI3vHAcTg3cQg= X-Envelope-To: linux-arm-kernel@lists.infradead.org Received: by smtp.migadu.com with ESMTPS id 4c246dde72db0327; Fri, 06 Nov 2026 12:02:35 +0000 X-Mizu-Trace-ID: 4c246dde72db0327 X-Migadu-Flow: FLOW_OUT From: Fuad Tabba To: maz@kernel.org, tglx@kernel.org Cc: radu@rendec.net, lpieralisi@kernel.org, steven.price@arm.com, suzuki.poulose@arm.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, will@kernel.org, tabba@google.com Subject: [PATCH 2/3] irqchip/gic-v3-its: Order table zeroing before the GIC can see it Date: Fri, 6 Nov 2026 12:02:20 +0000 Message-ID: <20261106120221.347309-3-fuad.tabba@linux.dev> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20261106120221.347309-1-fuad.tabba@linux.dev> References: <20261106120221.347309-1-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-20261106_040237_846003_856EEE9B X-CRM114-Status: GOOD ( 12.81 ) 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 ITS driver allocates the GIC's tables as zeroed pages. It exposes the ITS tables and the vPE tables with a single store: a relaxed GITS_BASER or GICR_VPROPBASER write with Valid set, the relaxed GITS_CTLR write that enables the ITS, or a valid level-1 entry for a level-2 page. However, on a coherent table the zeroing isn't ordered before that store, so the GIC can read the page's previous contents as table entries (UNPREDICTABLE: IHI 0069H.b 5.2.1, and GICR_VPROPBASER.Z in 12.11). A level-2 page is published at runtime, while the GIC may be walking the same level-1 table for other IDs. Add a dma_wmb() at the end of its_alloc_pages_node(). It orders the zeroing before later stores to memory and to MMIO alike. Signed-off-by: Fuad Tabba --- Notes: herd7 -model aarch64.cat, the ITS modelled as an observer PE that reads a published entry (e), then through it the zeroed page (p): with no barrier the stale read is Sometimes, with dma_wmb()'s DMB OSHST it is Never. AArch64 MP+dmb.st+addr-its-l1 { 0:X0=p; 0:X1=e; 0:X2=0; 0:X3=1; 1:X1=e; 1:X0=p; p=1; } P0 | P1 ; STR X2,[X0] | LDR X4,[X1] ; DMB OSHST | ; STR X3,[X1] | EOR X5,X4,X4 ; | LDR X6,[X0,X5] ; exists (1:X4=1 /\ 1:X6=1) The model puts both PEs in one Inner Shareable domain, so it does not separate ISH from OSH. OSH reaches the GIC whichever domain it is in: DDI0487 B2.10.1.1 says Outer Shareable "applies across both the Inner Shareable and the Outer Shareable shareability domains". The register publishes (GITS_BASER, GITS_CTLR, GICR_VPROPBASER) are the writel() case: the same DMB OSHST ahead of a Device write. drivers/irqchip/irq-gic-v3-its.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c index de1f1b1f26623..badc3843d90ca 100644 --- a/drivers/irqchip/irq-gic-v3-its.c +++ b/drivers/irqchip/irq-gic-v3-its.c @@ -234,6 +234,9 @@ static struct page *its_alloc_pages_node(int node, gfp_t gfp, if (ret) return NULL; + /* Order the zeroing before any store that exposes the page to the GIC */ + dma_wmb(); + return page; } -- 2.47.3