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 B2674CCF2C4 for ; Sat, 17 Oct 2026 12:29:16 +0000 (UTC) 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:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=UZfuqqpj0acP+TZ78oFBFjQ3viEqF3GWFUTkEAuwr0U=; b=nKBYr/ea8GAC2/ yM3Gdift8n7IXZ8KkLPIDv63xOljP4ZrgqXwK167l7IwkTi4eBm9PNoRiiyygJUVedZoknssDGvN5 L9/QEra2uEky3jNNmnsDEC43/HPwdZIWsKUecQ+Ank6pwNkB+rERQhCdCO5vYAEjQZQM1lrIb7aSL Ydb95uZVn4+1EcUOiQl+ycuzA1lIlwVIfNuIDvfriUu1jkb3nxorpgi6wQhJ3Ot+lPInDeSqTY+yq onL0+as1ai4YbBEgNAy9lLJF0iPlr0JEclPsSBY2v6PNwvfKnqFJXUER2VQo2CWZkW7AAaiFrLXEc 1YgVXYK36jd4lJEAgS5Q==; 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arc=none smtp.client-ip=91.218.175.6 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="uEPEzbwH" X-Envelope-To: kvm@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=7cgiKM+zDuDnTZJRzu5yT4bUih3KcyLUsgr/rzH4uiM=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1792240147; v=1; x=1792844947; b=uEPEzbwHu/tt5chmzaFb5qbVqI83ww2eE1GF8KosR6AjlTOwmdTEqJ94CSeZ1UR51kiAx4qU CQ6i+LLjOUvmP5QAsneUi7HxbRTR4MpxqAxhRPKJiUN89DM6oNRSjQvW2EtOVpxuAxoyEjCMvhc HMVUxPFgifG0cH94YLDLxAvg= X-Envelope-To: kvm@vger.kernel.org Received: by smtp.migadu.com with ESMTPS id 4ced6db5906c4a15; Sat, 17 Oct 2026 12:29:07 +0000 X-Mizu-Trace-ID: 4ced6db5906c4a15 X-Migadu-Flow: FLOW_OUT Date: Sat, 17 Oct 2026 14:29:06 +0200 From: Andrew Jones To: Anup Patel Cc: Andrew Jones , kvm-riscv@lists.infradead.org, atish.patra@linux.dev, pjw@kernel.org, palmer@dabbelt.com, kvm@vger.kernel.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] RISC-V: KVM: Use a raw lock for IMSIC wakeup state Message-ID: References: <20260925155116.465203-1-andrew.jones@oss.qualcomm.com> <7zy352odf4hekcibmio3atunubffzxfcsqnn55q6sfkksnynfj@5bx263nnizdm> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Fri, Oct 09, 2026 at 06:37:13PM +0200, Anup Patel wrote: > On Fri, Oct 9, 2026 at 3:44 PM Andrew Jones > wrote: > > > > Hi Anup, > > > > On Fri, Oct 09, 2026 at 01:45:20PM +0200, Anup Patel wrote: > > > On Fri, Sep 25, 2026 at 5:51 PM Andrew Jones > > > wrote: > > > > > > > > kvm_riscv_vcpu_aia_imsic_put() can run from the scheduler preemption > > > > notifier while the raw runqueue lock is held. Taking vsfile_lock, an > > > > rwlock_t, there violates the lockdep wait-context rules. > > > > > > > > Protect the CPU/HGEI pair with a separate raw spinlock. All updates to > > > > that pair retain vsfile_lock and take the new lock, while scheduler-out > > > > uses only the new lock around the HGEIE update. This keeps the wakeup > > > > setup serialized with VS-file publication and release without bringing > > > > wider IMSIC operations into a raw critical section. > > > > > > Instead of introducing another lock, why not replace > > > read_lock_irqsave(&imsic->vsfile_lock, flags) with > > > write_lock_irqsave(&imsic->vsfile_lock, flags) in > > > kvm_riscv_vcpu_aia_imsic_put() ?? > > > > Unfortunately, write_lock_irqsave() has the same PREEMPT_RT issue, since > > rwlock_t is sleepable on RT in both modes. > > > > I am not fond of nested locking, why not convert vsfile_lock into raw > spinlock ?? > We can do that. The reader concurrency the rwlock gave us was only for tiny sections anyway. I'll send a v2. Thanks, drew