From nobody Wed Dec 17 12:42:23 2025 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 79D7AA50; Wed, 12 Feb 2025 00:45:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739321131; cv=none; b=HuylgyiuG+e3rCW3P+825pOvXu4eEEoHtwAc+9mafw00iFXEnxTmMQwSRBYJ1ih8CqMuPF7xHSF9HHkiLrO2J9kPOaI6apYLHetKf7Gme5stUH3DN6fgHpyQjjrAuJ6ofRwO3zmrHYL1BoI4tzrskaSuAkRY9Ywmu9yPcoylVLU= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739321131; c=relaxed/simple; bh=5rRoChObeNqNxfmbCbT8iUIfiBHkKWAFVjiyqgK4VdI=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:To:Cc; b=YeqZ0z0NfcyK2P2A7eEX7EhLt+iMzlrsuSq3zYousAJ2lCGqNl9jEJBo71/J9BkCnraEErlq1A3iRTb9vz5MwMsJTELhd2+tfyhH2WCJAKawEQXEpaHcfYyzFmON5Soq3DhNXdKY/bPwukWhZF3qXtpFrADBlVHlGefjPqJ85hQ= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=lpFYXFUt; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="lpFYXFUt" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8EDBBC4CEDD; Wed, 12 Feb 2025 00:45:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1739321130; bh=5rRoChObeNqNxfmbCbT8iUIfiBHkKWAFVjiyqgK4VdI=; h=From:Date:Subject:To:Cc:From; b=lpFYXFUt+KAocrDCcNBlhRj+YexM6svmmv4blnBwr7/gvIS9+zIFa2M0plNMl0vIH egkj2HURSf4Yz6L7zsKrF+g4KSONRNDVuTrLYiIv5LPewE3N7dZNY3f4HzYn6Laqc5 8bLm4IlbNyv05uJZfeCKuIfpArbkGgCT+7gKAFzvC40HA+iKQB1AMrqQsMna0HsvUX vhlHU5x/Lks1kf0dytJd8JBlwm5jIRsFTHuVrWyWPkxzTfvfU6GJO+aP/CEkj0XB6f HMLDIzLgeqkDXBeMcPGUHnz4+lUPlsVk0dZssZ3PNLE16oOah8UPNVRmgNiiLMIa1N QDEcxZzugEODA== From: Mark Brown Date: Wed, 12 Feb 2025 00:44:57 +0000 Subject: [PATCH v7] KVM: arm64: Fix confusion in documentation for pKVM SME assert Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20250212-kvm-arm64-sme-assert-v7-1-0f786db838d3@kernel.org> X-B4-Tracking: v=1; b=H4sIAAjvq2cC/4XO3UrEMBAF4FdZcm0kPzNp4pXvIV7kr7thbSvJE pSl7266oKuU4OUZON+ZKykxp1jI0+FKcqyppGVuYXg4EH+y8zHSFFomgglgigE914naPCmgZYr Ulta/ULRhQAwQtVWkVd9zHNPHjX15bfmUymXJn7eVyrfrP2DllFMMRkvQgbFRP59jnuPb45KPZ BOr+K1gRxGbAtJwx5gUI+wUeVcGyTqKbIpWxgBCRO/2v8BdMV0FmiK9CePAg1N6r+CPwgXvKdg UY9DrEDgT6HaK+laQ9RXVFO+F8qACdyD/KOu6fgHzMGksFwIAAA== X-Change-ID: 20240604-kvm-arm64-sme-assert-5ad755d4e8a6 To: linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-kernel@vger.kernel.org Cc: Fuad Tabba , Mark Brown , Marc Zyngier , Oliver Upton , James Morse , Suzuki K Poulose , Catalin Marinas , Will Deacon , Mark Rutland X-Mailer: b4 0.15-dev-1b0d6 X-Developer-Signature: v=1; a=openpgp-sha256; l=3561; i=broonie@kernel.org; h=from:subject:message-id; bh=5rRoChObeNqNxfmbCbT8iUIfiBHkKWAFVjiyqgK4VdI=; b=owEBbQGS/pANAwAKASTWi3JdVIfQAcsmYgBnq+8nYl1hKlgAf8UHLSYhrZpD14NjnmH5zjzaln2A iud10pqJATMEAAEKAB0WIQSt5miqZ1cYtZ/in+ok1otyXVSH0AUCZ6vvJwAKCRAk1otyXVSH0LWKB/ 9WcV7yweaKsEXcht6lTbS/nW+jDulcbredFQ/S5R3OBygrOiXxhYUMUhYQlRIExRnXH0PDMZTvaSoQ zMyBGJN9tL1+P8UhBZTQGSqJp5Gl2l8g92E0lzW25OMVlUwPh6+znCOVyuB311NRYle1PwpH+jHfWv Nl76YHN6j2/owhMof3gXUwZ5u3rgiM56wATZzD0IlpoqG34LEqY1TEHn0k+J4CYcZrjJOZH3aynwLC QcigqJizzoQ1tYUz1QBgmMYNE1g+bm06HQFRe+BZRLY3wzI7OR7FDV7RhoVuI31EY19Py9KCA53Fpb epELU9TEUOZqVllh1DSdfdIRe/PAbq X-Developer-Key: i=broonie@kernel.org; a=openpgp; fpr=3F2568AAC26998F9E813A1C5C3F436CA30F5D8EB As raised in the review comments for the original patch the assert and comment added in afb91f5f8ad7 ("KVM: arm64: Ensure that SME controls are disabled in protected mode") are bogus. The comments says that we check that we do not have SME enabled for a pKVM guest but the assert actually checks to see if the host has anything set in SVCR which is unrelated to the guest features or state, regardless of if those guests are protected or not. This check is also made in the hypervisor, it will refuse to run a guest if the check fails, so it appears that the assert here is intended to improve diagnostics. Update the comment to reflect the check in the code, and to clarify that we do actually enforce this in the hypervisor. While we're here also update to use a WARN_ON_ONCE() to avoid log spam if this triggers. Fixes: afb91f5f8ad7 ("KVM: arm64: Ensure that SME controls are disabled in = protected mode") Reviewed-by: Fuad Tabba Signed-off-by: Mark Brown Acked-by: Mark Rutland --- This has been sent with v6.10 with only positive review comments after the first revision, if there is some issue with the change please share it. To: Marc Zyngier To: Oliver Upton To: James Morse To: Suzuki K Poulose To: Catalin Marinas To: Will Deacon To: Fuad Tabba Cc: Mark Rutland --- Changes in v7: - Reword the comment. - Link to v6: https://lore.kernel.org/r/20250210-kvm-arm64-sme-assert-v6-1-= cc26c46d1b43@kernel.org Changes in v6: - Rebase onto v6.14-rc1. - Link to v5: https://lore.kernel.org/r/20241210-kvm-arm64-sme-assert-v5-1-= 995c8dd1025b@kernel.org Changes in v5: - Rebase onto v6.13-rc1. - Link to v4: https://lore.kernel.org/r/20240930-kvm-arm64-sme-assert-v4-1-= 3c9df71db688@kernel.org Changes in v4: - Rebase onto v6.12-rc1 - Link to v3: https://lore.kernel.org/r/20240730-kvm-arm64-sme-assert-v3-1-= 8699454e5cb8@kernel.org Changes in v3: - Rebase onto v6.11-rc1. - Link to v2: https://lore.kernel.org/r/20240605-kvm-arm64-sme-assert-v2-1-= 54391b0032f4@kernel.org Changes in v2: - Commit message tweaks. - Change the assert to WARN_ON_ONCE(). - Link to v1: https://lore.kernel.org/r/20240604-kvm-arm64-sme-assert-v1-1-= 5d98348d00f8@kernel.org --- arch/arm64/kvm/fpsimd.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) diff --git a/arch/arm64/kvm/fpsimd.c b/arch/arm64/kvm/fpsimd.c index 4d3d1a2eb157047b4b2488e9c4ffaabc6f5a0818..e37e53883c357093ff4455f5afd= aec90e662d744 100644 --- a/arch/arm64/kvm/fpsimd.c +++ b/arch/arm64/kvm/fpsimd.c @@ -93,11 +93,14 @@ void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu) } =20 /* - * If normal guests gain SME support, maintain this behavior for pKVM - * guests, which don't support SME. + * Protected and non-protected KVM modes require that + * SVCR.{SM,ZA} =3D=3D {0,0} when entering a guest so that no + * host/guest SME state needs to be saved/restored by hyp code. + * + * In protected mode, hyp code will verify this later. */ - WARN_ON(is_protected_kvm_enabled() && system_supports_sme() && - read_sysreg_s(SYS_SVCR)); + WARN_ON_ONCE(is_protected_kvm_enabled() && system_supports_sme() && + read_sysreg_s(SYS_SVCR)); } =20 /* --- base-commit: 2014c95afecee3e76ca4a56956a936e23283f05b change-id: 20240604-kvm-arm64-sme-assert-5ad755d4e8a6 Best regards, --=20 Mark Brown