From: Sean Christopherson <seanjc@google.com>
To: David Woodhouse <dwmw2@infradead.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
Paul Durrant <paul@xen.org>,
Peter Zijlstra <peterz@infradead.org>,
Will Deacon <will@kernel.org>, Boqun Feng <boqun@kernel.org>,
Waiman Long <longman@redhat.com>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Clark Williams <clrkwllms@kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-rt-devel@lists.linux.dev,
Mauricio Faria de Oliveira <mfo@igalia.com>,
kernel-dev@igalia.com,
syzbot+208f7f3e5f59c11aeb90@syzkaller.appspotmail.com
Subject: Re: [PATCH 4/7] KVM: x86/xen: Remove unnecessary irqsave from GPC lock usage in xen.c
Date: Mon, 11 May 2026 09:51:07 -0700 [thread overview]
Message-ID: <agII-2_f_gYMdPzL@google.com> (raw)
In-Reply-To: <20260508181717.3230988-5-dwmw2@infradead.org>
On Fri, May 08, 2026, David Woodhouse wrote:
> From: David Woodhouse <dwmw@amazon.co.uk>
>
> Now that the hardirq path (xen_timer_callback and set_evtchn_fast) uses
> read_trylock() instead of read_lock_irqsave(), the remaining GPC lock
> users in xen.c are only called from process context (vcpu_run, ioctls).
> There is no need to disable interrupts to prevent concurrent access from
> a hardirq user, since the hardirq path no longer takes the lock.
No longer _waits_ on the lock, correct? I.e. the hardirq path can still take the
lock, but only ever does so using trylock.
next prev parent reply other threads:[~2026-05-11 16:51 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-08 18:10 [PATCH 0/7] KVM: x86/xen: Fix Xen / GPC / PREEMPT_RT issues with rwlock_t David Woodhouse
2026-05-08 18:10 ` [PATCH 1/7] locking/rt: Use raw_spin_lock_irqsave() in __rwbase_read_unlock() David Woodhouse
2026-05-08 18:10 ` [PATCH 2/7] KVM: x86: Use gfn_to_pfn_cache for record_steal_time David Woodhouse
2026-05-08 18:10 ` [PATCH 3/7] KVM: x86/xen: Use read_trylock() for GPC locks in hardirq/atomic paths David Woodhouse
2026-05-08 18:10 ` [PATCH 4/7] KVM: x86/xen: Remove unnecessary irqsave from GPC lock usage in xen.c David Woodhouse
2026-05-11 16:51 ` Sean Christopherson [this message]
2026-05-11 16:54 ` David Woodhouse
2026-05-11 17:48 ` Sean Christopherson
2026-05-11 18:12 ` David Woodhouse
2026-05-08 18:10 ` [PATCH 5/7] KVM: x86: Remove unnecessary irqsave from kvm_setup_guest_pvclock() David Woodhouse
2026-05-08 18:10 ` [PATCH 6/7] KVM: Remove unnecessary IRQ disabling from GPC lock in pfncache.c David Woodhouse
2026-05-08 18:10 ` [PATCH 7/7] KVM: x86/xen: Handle pending Xen timer events in vcpu_enter_guest() David Woodhouse
2026-05-09 7:27 ` David Woodhouse
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