From nobody Sun Feb 8 15:46:40 2026 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 DB24619D882; Mon, 10 Feb 2025 21:33:47 +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=1739223228; cv=none; b=MtyOMKm/mPJFHEaesDpvSdN1RX0XR/iarThu1bGDChwAL9OabNXi7ikCSOBQlvAJLGoUK7FZrc6iFi6P3IuL1JBj6IJ0YJlehi2EMa3PoqSSr2oJEa1U6XWkOh7J2j4neJbTWhemth8tNNfmkASwonNYILDkK04baTe37s8NCps= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739223228; c=relaxed/simple; bh=1drrGjPU44nrH4vEhvtFt2+xQt61WJAY+SI+N/d+RYI=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:To:Cc; b=J0ofohVkBDxVayMIRdLFGe0DCoD2JFbs7FBdeWNYEijp/pDNRJm4yPuKWpjBjDZmROXgClTXi3E6My5LeB30H5d1Tny4f6dywWwAvpOOEj8l8aGldcdMj+DO0mv96bjzIghicXW5v4DIumXz9Qp68zaMGxGkG1XBEXsN947fCYA= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=mmG2C0je; 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="mmG2C0je" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2D4E3C4CED1; Mon, 10 Feb 2025 21:33:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1739223227; bh=1drrGjPU44nrH4vEhvtFt2+xQt61WJAY+SI+N/d+RYI=; h=From:Date:Subject:To:Cc:From; b=mmG2C0jeXE/CmSjuTtgvhykEJM34pFG7DAzLJHNLh8v+OoLq0J4WFolOo4zcbd3o/ ouefM9vIw85T+xWG2N67yQFZftsZ2mo2hufZ3Hj9fBzWaIYUab6QYSpVwOrgJNjFL9 tDSUyIF2vIWbqkErpzUQlR9rcFke9DGiYXzekLvpTZwEB30yN47RWMrBnRQ4JDT5zN 0L9BK4dnHz/q24yJPrNiKNSGMQ8TNIY+TzUOEWbdJTUsCiOlujdD3n4qFRlKlKa/oK fHoJz8aJpJDaZgwomMKm5pWiyadmVAJAu0WUCtgavX4Tll802OXKyeLzh9M3GE2tkY aW41wjqNyqHOA== From: Mark Brown Date: Mon, 10 Feb 2025 21:33:32 +0000 Subject: [PATCH v6] 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: <20250210-kvm-arm64-sme-assert-v6-1-cc26c46d1b43@kernel.org> X-B4-Tracking: v=1; b=H4sIAKtwqmcC/4XOTWrDMBAF4KsEraugnxlZyqr3KF3I1jgRqe0iB dESfPfIWSQpxnT5Bt735soypUiZHXZXlqjEHKexBvO2Y93Jj0fiMdTMlFAgjAB+LgP3aTDA80D c59q/cPShQQxA1htWq9+J+vhzZz8+az7FfJnS732lyOX6D1gklxyDsxpsEKK372dKI33tp3Rki 1jUq4IbiloU0E62QmjVw0rRT6XRYkPRVbHGOUAg7Nr1L/BU3KYCVdGdC30jQ2vsWsGHIpXcUrA qzmFnQ5BCYftHmef5BiTHWX7RAQAA 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 X-Mailer: b4 0.15-dev-1b0d6 X-Developer-Signature: v=1; a=openpgp-sha256; l=3413; i=broonie@kernel.org; h=from:subject:message-id; bh=1drrGjPU44nrH4vEhvtFt2+xQt61WJAY+SI+N/d+RYI=; b=owEBbQGS/pANAwAKASTWi3JdVIfQAcsmYgBnqnC43KKyMdIxyNNobIHVoI2JQC7uPgVNQ/dl5F3p CqbB6wOJATMEAAEKAB0WIQSt5miqZ1cYtZ/in+ok1otyXVSH0AUCZ6pwuAAKCRAk1otyXVSH0A53B/ 4r8V5baaTij1dC0zc+elLFiunWYoPKygp7SljVQVt7tJ6OZ7KAXuWorppwOIG53GLBGoSTmLXWpFfu /+cw93KAqqZylfxwmY7gM4UTWb8IelfkUgdiq3kZUz7YaZZMGD3NHr2WUdJZ7ImUHkvyrnC0XIq8++ vzhkfUlhmU+8x8pAn3+XNTDhnlAI/aEGtlLl/+E0oZrWUZWevnVW8PRPvKeij/VHtBt8ZJaDfkXpWb JrCj8ZrKAkg4JA8wUPD/wrmB5Y9YdTc4xP7l+8HiEW/hFr/1KTJ00REz/nLlOppMxDM2biQrwPgigg TVDtfubygHXOum7KtekJbAsH6sbibu 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 --- 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 --- 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..f3455641e9c8a65470cdeb9d7da= ba7d59d78748e 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. + * The pKVM hypervisor does not yet understand how to save or + * restore SME state for the host so double check that if we + * are running with pKVM we have disabled SME. The hypervisor + * enforces this when the guest is run, this check is for + * clearer diagnostics. */ - 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