From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=91.218.175.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1792430178; b=ghFS0uiwfv7hAldk9JxyMv6jBJuryq+/4AV5nEvcy6NyogXHTv465nn+nUcwxMdCNlb+ LY5N2d0Rr5iY1hhzQrXjXj45wdFbg9U0YIfECFxZLeiJYypdR83S1ydMxj4fNoqJftXYq HNpBcisUA5RyWJUnlsdj4ykgoR8LEbyKWyXqZVa1Sp2BYVrDCBcKUNebgj2P5YT/BxXZQ wqzCJk/pLpXh2zsBiGIAPEy9zAzr/YaDBWz7eWnGsaSwQn42tbPZ+cpwAYoPQ5dXm/xLC RWd94ZO82JnuYRPbX9zpuG1eEeHXU1x3TqSYFUS+P6opIPKViXerjxP5KUN0s9iOedQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1792430178; h=DMARC-Filter:X-Envelope-To:DKIM-Signature:X-Envelope-To:Received: X-Mizu-Trace-ID:X-Migadu-Flow:Date:From:To:Cc:Subject:Message-ID: References:MIME-Version:Content-Type:Content-Disposition:In-Reply-To; bh=qNx6DHkaVsiPl/g7Htua0EzSABv4CXVzJo807UeBYIU=; b=sErOw8xNAlEpt8+DAMloBnuB1jQnK8+Qd4ioqjlCvwLew+QOyalhG3P91Z5NFW2S/IaR 2ftSeYdwHiN0NrJEExzlP1yDiDxsRpmZffZ5J7ur6LUvqpaAJEmxKYS5BCUJNCQXMmHFS 8bOCVJfFLKuFku+PYoZVqcqpe99WxkHK2linKv1GztsxlLoEzyaVPw/P24pRMHk1hFuC4 IjrrxwhDEUaFsUtnikd/FTKpB+QEr6fkSTMz1+WX6PaCUM0sN0vrbvxB3Jdjm+Zfqa/Xm VKbzIbjT42ofZEvtY6FR57DEuJEmFQg/5DQaAaAwTiISllQwstWE3+2ZaCuzDt1CVQw== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256 header.s=key1 header.b=A1oEpCFf; arc=none smtp.remote-ip=91.218.175.18 Received: from mta0.migadu.com (out-18.mta0.migadu.com [91.218.175.18]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9A436606A319 for ; Mon, 19 Oct 2026 17:16:16 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 9A436606A319 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, unprotected) header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256 header.s=key1 header.b=A1oEpCFf X-Envelope-To: linux-kernel@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=Ht0YeVNr87GBjD/XD3J4ka9N9ZFBQ94E02FEAUKrXMQ=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1792430171; v=1; x=1793034971; b=A1oEpCFfgn7hY8SlFJYdcXt93AMGLNPWFV8GWG+ZlKxM7ik9DPXqhPKqZVZcHyy62OPoWRJS 3Bzu7/+WNZSXmcOG1e0/5m+jZ6/1/FbsFujaduXfb0RTbYmXaDsBDmoMRLMuiWJ7va3EPg8IDdx 3kbwcTeZC2SYBAaqOkRofq4k= X-Envelope-To: linux-kernel@vger.kernel.org Received: by smtp.migadu.com with ESMTPS id 6fce2d4bfa616019; Mon, 19 Oct 2026 17:16:10 +0000 X-Mizu-Trace-ID: 6fce2d4bfa616019 X-Migadu-Flow: FLOW_OUT Date: Mon, 19 Oct 2026 19:16:06 +0200 From: Andrew Jones To: kvm-riscv@lists.infradead.org Cc: anup@brainfault.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 v2] RISC-V: KVM: Convert IMSIC vsfile_lock to a raw spinlock Message-ID: References: <20261019134709.2610129-1-andrew.jones@linux.dev> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261019134709.2610129-1-andrew.jones@linux.dev> On Mon, Oct 19, 2026 at 03:47:09PM +0200, Andrew Jones wrote: > kvm_riscv_vcpu_aia_imsic_put() runs from the scheduler preemption > notifier with the raw runqueue lock held, so it must not take > vsfile_lock, an rwlock_t, which sleeps on PREEMPT_RT. All vsfile_lock > critical sections are short, so a raw spinlock is fine. > > Fixes: 4cec89db80ba ("RISC-V: KVM: Move HGEI[E|P] CSR access to IMSIC virtualization") > Signed-off-by: Andrew Jones > --- > v2: > - Convert vsfile_lock to raw_spinlock_t instead of adding a separate > hgei_lock [Anup] Hi Anup, Sashiko found an ABBA deadlock with this v2[1]. Making vsfile_lock exclusive serializes kvm_riscv_vcpu_aia_imsic_put(), which runs under rq->__lock, against the SW-file inject paths, which kick the vCPU (pi_lock/rq->__lock) while holding vsfile_lock. Lockdep confirms it with an EMUL mode guest, and the host then hangs (I should have tested with EMUL before...). v1 doesn't have the problem, since its hgei_lock never has anything that wakes tasks nested under it. I tested v1 in both EMUL mode and hwaccel mode [again] with lockdep and it's good. Should we take v1 instead? [1] https://sashiko.dev/#/patchset/20261019134709.2610129-1-andrew.jones@linux.dev?part=1 Thanks, drew