From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 3710123E33D; Tue, 13 Oct 2026 12:44:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791895464; cv=none; b=odB5kPTsPTobbDi1LNeWrUhgMMqFTbv8uhvdMm0JqUyVdKYIFSj9RGnXl9x/wOhAPe34OcV17a350l6wlQ0uItEZuiZVaay3aRon6sN+uf2jY3vXBKuPduKf5ls99FBOzL8pLvdj+5iwUkRg4XDGEB10P5TzirnmPQUYgpYiWBc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791895464; c=relaxed/simple; bh=JwLKeyrDQWWaIouZhcpnOkV63NeD106oUeL4Kp5MwzU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=KYdxdVMiN0R9o9o+GcB1lafd0OKe3rpaFHTeSadymjwna2cjVZSZD7fLEt1pmMR+goopF6paBWPCBfJUfQEaybq7Fvq/cJ2dJnQDq6IXIS4nG8zGqqZuxF7njmc0fn96orqKNhIMI4ydyT0jjGD7kyiMwYsFRXgcMpfwQ7pn7eU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=lf28/jsR; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="lf28/jsR" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 44CA61F00898; Tue, 13 Oct 2026 12:44:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1791895462; bh=aGBEWstA6p/WrvKysEMTTqjkxk9zIbdmFqmBLlNDeEc=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=lf28/jsRlxtcc3+GjjTIKE2ojkT8Cu3Kv1Y/icbs2Pj13esEQ2QZpT3uFa/UByqX/ 493mSQu4EpMjnvVu3gb0ZIg/FhDpxO0/33pYttgN9RluMzInwW1YhUHHRie7+Uo1Fs DS9zQ5OeeaXgsucDxnQEDdx5mMz2uf+dBgzV048M= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Mark Rutland , Catalin Marinas , Marc Zyngier , Mark Brown , Will Deacon , Sasha Levin Subject: [PATCH 6.12 284/497] arm64/fpsimd: signal: Mandate SVE payload for streaming-mode state Date: Tue, 13 Oct 2026 13:37:31 +0200 Message-ID: <20261013112914.635129133@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261013112907.864180619@linuxfoundation.org> References: <20261013112907.864180619@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Mark Rutland [ Upstream commit b465ace42620970e840c7aeb2c44a6e3b1002fec ] Non-streaming SVE state may be preserved without an SVE payload, in which case the SVE context only has a header with VL==0, and all state can be restored from the FPSIMD context. Streaming SVE state is always preserved with an SVE payload, where the SVE context header has VL!=0, and the SVE_SIG_FLAG_SM flag is set. The kernel never preserves an SVE context where SVE_SIG_FLAG_SM is set without an SVE payload. However, restore_sve_fpsimd_context() doesn't forbid restoring such a context, and will handle this case by clearing PSTATE.SM and restoring the FPSIMD context into non-streaming mode, which isn't consistent with the SVE_SIG_FLAG_SM flag. Forbid this case, and mandate an SVE payload when the SVE_SIG_FLAG_SM flag is set. This avoids an awkward ABI quirk and reduces the risk that later rework to this code permits configuring a task with PSTATE.SM==1 and fp_type==FP_STATE_FPSIMD. I've marked this as a fix given that we never intended to support this case, and we don't want anyone to start relying upon the old behaviour once we re-enable SME. Fixes: 85ed24dad290 ("arm64/sme: Implement streaming SVE signal handling") Signed-off-by: Mark Rutland Cc: Catalin Marinas Cc: Marc Zyngier Cc: Mark Brown Cc: Will Deacon Reviewed-by: Mark Brown Link: https://lore.kernel.org/r/20250508132644.1395904-4-mark.rutland@arm.com Signed-off-by: Will Deacon Signed-off-by: Sasha Levin --- arch/arm64/kernel/signal.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c index 6a5d83d9179da..fc817154e8990 100644 --- a/arch/arm64/kernel/signal.c +++ b/arch/arm64/kernel/signal.c @@ -392,6 +392,7 @@ static int restore_sve_fpsimd_context(struct user_ctxs *user) unsigned int vl, vq; struct user_fpsimd_state fpsimd; u16 user_vl, flags; + bool sm; if (user->sve_size < sizeof(*user->sve)) return -EINVAL; @@ -401,7 +402,8 @@ static int restore_sve_fpsimd_context(struct user_ctxs *user) if (err) return err; - if (flags & SVE_SIG_FLAG_SM) { + sm = flags & SVE_SIG_FLAG_SM; + if (sm) { if (!system_supports_sme()) return -EINVAL; @@ -421,7 +423,16 @@ static int restore_sve_fpsimd_context(struct user_ctxs *user) if (user_vl != vl) return -EINVAL; - if (user->sve_size == sizeof(*user->sve)) { + /* + * Non-streaming SVE state may be preserved without an SVE payload, in + * which case the SVE context only has a header with VL==0, and all + * state can be restored from the FPSIMD context. + * + * Streaming SVE state is always preserved with an SVE payload. For + * consistency and robustness, reject restoring streaming SVE state + * without an SVE payload. + */ + if (!sm && user->sve_size == sizeof(*user->sve)) { clear_thread_flag(TIF_SVE); current->thread.svcr &= ~SVCR_SM_MASK; current->thread.fp_type = FP_STATE_FPSIMD; -- 2.53.0