From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 0B045109449E for ; Sat, 21 Mar 2026 21:24:51 +0000 (UTC) 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-Owner; bh=VwI+iFC+os0LZiR8h0XoComz3kCMJYNiLXeP8+W/HoQ=; b=cOPKpzWw11nFJZdg9OcwCKwghq FIJ7mUHk/IpB7pxJUhvUo/r/kGja4UOowG1Kui7cYkBkpfPi1OfoamYIN2I/RzYz2rUSc9fLDhtsh 95/QVxbZ+EEYCeUIeFQ74E5pkf/zREOXf7FRo76ZS2wE3CpV0iPF0vUe02rHmzyGBrYcQSBvgnyXu BTx7POEqQh1RoFhFl8VmIDvVXujBKciTnCsEWzrqyojL9/v/J92FybaSXPaWd4NCiqVomqFLhjVZu ou1DKQBlxz0HG/PPN6Aj+643YPuqqLRAaDF9L/NJbA4xBav8Q0bxmf/3gQmcAE0LW/PpcetqSv0Xw wpGyNCjA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1w43oN-0000000EnqI-0VOO; Sat, 21 Mar 2026 21:24:47 +0000 Received: from sea.source.kernel.org ([2600:3c0a:e001:78e:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1w43oG-0000000EnnC-1DNY for linux-arm-kernel@lists.infradead.org; Sat, 21 Mar 2026 21:24:41 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id CE2A344592; Sat, 21 Mar 2026 21:24:38 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id AC1ABC19421; Sat, 21 Mar 2026 21:24:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1774128278; bh=8bzD2dk+uDzAASOAfcr9mx9j08i2ZacZn3lcDkDtgcI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=J/qjAeiUXbzQ6Ihtts0wvJIaBxgcU8nZ1ymWN86N26Su5HuC8vECXupgUP9rcd8Rk 2dDTrcI6HCMEm6NUXDvmIHm9HODPslNfrn8QvW58L/uYxYJkVW6XeUwhDPtczhgDP0 edE9qpPx8me7UNYUIHQy7XPXKX27QNSTYDOn9WaM8gDx1k2hpzV7vZu6rTjgDysXLX FwmyJSkBZEwIik/BDgAkvY8xogXgGkeZLofyW6yWueST51BCfldeho3pd9i/VKw8su LNUNxwvO0cAQlL5FY82/eyvJsx3u3rW5jAMBAeyyb+lUDSTa8ghA/htXohtvByrD5J ATRYhxH5p9G9g== Received: from sofa.misterjones.org ([185.219.108.64] helo=valley-girl.lan) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.98.2) (envelope-from ) id 1w43oD-00000004NPB-00TM; Sat, 21 Mar 2026 21:24:37 +0000 From: Marc Zyngier To: kvmarm@lists.linux.dev, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org Cc: Joey Gouly , Suzuki K Poulose , Oliver Upton , Zenghui Yu , Fuad Tabba , Will Deacon , Mostafa Saleh , Quentin Perret Subject: [PATCH 5/5] KVM: arm64: Remove extra ISBs when using msr_hcr_el2 Date: Sat, 21 Mar 2026 21:24:19 +0000 Message-ID: <20260321212419.2803972-6-maz@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260321212419.2803972-1-maz@kernel.org> References: <20260321212419.2803972-1-maz@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: kvmarm@lists.linux.dev, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, joey.gouly@arm.com, suzuki.poulose@arm.com, oupton@kernel.org, yuzenghui@huawei.com, tabba@google.com, will@kernel.org, smostafa@google.com, qperret@google.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260321_142440_365406_C6B55880 X-CRM114-Status: GOOD ( 12.13 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org The msr_hcr_el2 macro is slightly awkward, as it provides an ISB when CONFIG_AMPERE_ERRATUM_AC04_CPU_23 is present, and none otherwise. Note that this this option is 'default y', meaning that it is likely to be selected. Most instances of msr_hcr_el2 are also immediately followed by an ISB, meaning that in most cases, you end-up with two back-to-back ISBs. This isn't a big deal, but once you have seen that, you can't unsee it. Rework the msr_hcr_el2 macro to always provide the ISB, and drop the superfluous ISBs everywhere else. Signed-off-by: Marc Zyngier --- arch/arm64/include/asm/el2_setup.h | 2 -- arch/arm64/include/asm/sysreg.h | 6 ++---- arch/arm64/kernel/hyp-stub.S | 1 - arch/arm64/kvm/hyp/nvhe/host.S | 1 - 4 files changed, 2 insertions(+), 8 deletions(-) diff --git a/arch/arm64/include/asm/el2_setup.h b/arch/arm64/include/asm/el2_setup.h index 85f4c1615472d..3e58d6264581e 100644 --- a/arch/arm64/include/asm/el2_setup.h +++ b/arch/arm64/include/asm/el2_setup.h @@ -50,7 +50,6 @@ * effectively VHE-only or not. */ msr_hcr_el2 x0 // Setup HCR_EL2 as nVHE - isb mov x1, #1 // Write something to FAR_EL1 msr far_el1, x1 isb @@ -64,7 +63,6 @@ .LnE2H0_\@: orr x0, x0, #HCR_E2H msr_hcr_el2 x0 - isb .LnVHE_\@: .endm diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h index f4436ecc630cd..ca66b8017fa87 100644 --- a/arch/arm64/include/asm/sysreg.h +++ b/arch/arm64/include/asm/sysreg.h @@ -1114,11 +1114,9 @@ .macro msr_hcr_el2, reg #if IS_ENABLED(CONFIG_AMPERE_ERRATUM_AC04_CPU_23) dsb nsh - msr hcr_el2, \reg - isb -#else - msr hcr_el2, \reg #endif + msr hcr_el2, \reg + isb // Required by AMPERE_ERRATUM_AC04_CPU_23 .endm #else diff --git a/arch/arm64/kernel/hyp-stub.S b/arch/arm64/kernel/hyp-stub.S index 085bc9972f6bb..634ddc9042444 100644 --- a/arch/arm64/kernel/hyp-stub.S +++ b/arch/arm64/kernel/hyp-stub.S @@ -103,7 +103,6 @@ SYM_CODE_START_LOCAL(__finalise_el2) // Engage the VHE magic! mov_q x0, HCR_HOST_VHE_FLAGS msr_hcr_el2 x0 - isb // Use the EL1 allocated stack, per-cpu offset mrs x0, sp_el1 diff --git a/arch/arm64/kvm/hyp/nvhe/host.S b/arch/arm64/kvm/hyp/nvhe/host.S index 465f6f1dd6414..ff10cafa0ca81 100644 --- a/arch/arm64/kvm/hyp/nvhe/host.S +++ b/arch/arm64/kvm/hyp/nvhe/host.S @@ -125,7 +125,6 @@ SYM_FUNC_START(__hyp_do_panic) mrs x0, hcr_el2 bic x0, x0, #HCR_VM msr_hcr_el2 x0 - isb tlbi vmalls12e1 dsb nsh #endif -- 2.47.3