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([27.4.76.112]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2b27477c54bsm12480875ad.27.2026.04.01.18.30.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 01 Apr 2026 18:31:00 -0700 (PDT) From: "shaikh.kamal" To: kvm@vger.kernel.org Cc: seanjc@google.com, pbonzini@redhat.com, dwmw@amazon.co.uk, linux-kernel@vger.kernel.org, syzbot+919877893c9d28162dc2@syzkaller.appspotmail.com, skhan@linuxfoundation.org, me@brighamcampbell.com, "shaikh.kamal" Subject: [PATCH v2 0/1] KVM: x86/xen: Fix PREEMPT_RT sleeping lock bug Date: Thu, 2 Apr 2026 07:00:22 +0530 Message-ID: <20260402013022.21879-1-shaikhkamal2012@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Hi Sean, Thanks for the detailed feedback. I've implemented v2 using unconditional read_trylock() as you suggested. Changes in v2: - Use read_trylock() unconditionally (no in_hardirq() check) - Apply trylock to both gpc lock acquisitions - Return -EWOULDBLOCK on contention to use existing slow path Changes from v1: - v1 used irq_work deferral (rejected for code duplication) - v2 uses trylock, leveraging existing slow path (cleaner) Testing: - PREEMPT_RT kernel: No crash with syzbot reproducer after 30+ min - non-RT kernel: No regression This minimal fix preserves compatibility with your planned gpc API cleanup. Thanks, Kamal shaikh.kamal (1): KVM: x86/xen: Use trylock for fast path event channel delivery arch/x86/kvm/xen.c | 33 +++++++++++++++++++++++++++++---- 1 file changed, 29 insertions(+), 4 deletions(-) -- 2.43.0