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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 19091C433F5 for ; Thu, 28 Oct 2021 11:18:58 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id E1864610FC for ; Thu, 28 Oct 2021 11:18:57 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org E1864610FC Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:Cc:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=cPHQ7vHClWu86LVgepDo55SVLouAi+lbFHaXI897BEE=; b=b00LlCo3ZS9rW9 ZWmSQGdzvMzZNQqOGDwPhfyno3NaEpo8u+DcygvebzlP2GI+LKfzKtDvqJ82OlLHvC+fmxhoK0rXm iCN3aRyHvuezPuGZwUrihEFrxFG3X0T2jzTgVTM8qoiqDCdBvhhfGMXNDao5lslkFBhq6u5onMl8z hWU/N8FGMuSBmawQP352xayZKAOlPeCZI+BI44CajZzWmzAxw7PZetTqvW7DwCnCs8UOzAev81BE4 z/y7viwxaAey5to7SA7gV6CX3xlQhi3QFnchmr9GcuIExzML55dy5U+4mSu5iYTUeq90BdrseW0/P Wt90tBPUvdVHovrS5mxA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mg3Pg-007eUG-G1; Thu, 28 Oct 2021 11:17:40 +0000 Received: from mail.kernel.org ([198.145.29.99]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1mg3Oq-007eG6-68 for linux-arm-kernel@lists.infradead.org; Thu, 28 Oct 2021 11:16:49 +0000 Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 1089E6112E; Thu, 28 Oct 2021 11:16:47 +0000 (UTC) Received: from sofa.misterjones.org ([185.219.108.64] helo=why.lan) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1mg3On-002BtD-6b; Thu, 28 Oct 2021 12:16:45 +0100 From: Marc Zyngier To: kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org Cc: James Morse , Suzuki K Poulose , Alexandru Elisei , Quentin Perret , Will Deacon , broonie@kernel.org, kernel-team@android.com Subject: [PATCH v2 5/5] arm64/fpsimd: Document the use of TIF_FOREIGN_FPSTATE by KVM Date: Thu, 28 Oct 2021 12:16:40 +0100 Message-Id: <20211028111640.3663631-6-maz@kernel.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20211028111640.3663631-1-maz@kernel.org> References: <20211028111640.3663631-1-maz@kernel.org> MIME-Version: 1.0 X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, james.morse@arm.com, suzuki.poulose@arm.com, alexandru.elisei@arm.com, qperret@google.com, will@kernel.org, broonie@kernel.org, kernel-team@android.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-20211028_041648_285484_0D733CFD X-CRM114-Status: GOOD ( 15.31 ) 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: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org The bit of documentation that talks about TIF_FOREIGN_FPSTATE does not mention the ungodly tricks that KVM plays with this flag. Try and document this for the posterity. Signed-off-by: Marc Zyngier --- arch/arm64/kernel/fpsimd.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c index ff4962750b3d..1fbd6ba7dbac 100644 --- a/arch/arm64/kernel/fpsimd.c +++ b/arch/arm64/kernel/fpsimd.c @@ -78,7 +78,11 @@ * indicate whether or not the userland FPSIMD state of the current task is * present in the registers. The flag is set unless the FPSIMD registers of this * CPU currently contain the most recent userland FPSIMD state of the current - * task. + * task. If the task is behaving as a VMM, then this is will be managed by + * KVM which will clear it to indicate that the vcpu FPSIMD state is currently + * loaded on the CPU, allowing the state to be saved if a FPSIMD-aware + * softirq kicks in. Upon vcpu_put(), KVM will save the vcpu FP state and + * flag the register state as invalid. * * In order to allow softirq handlers to use FPSIMD, kernel_neon_begin() may * save the task's FPSIMD context back to task_struct from softirq context. -- 2.30.2 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel