From: "Huang, Kai" <kai.huang@intel.com>
To: "sashiko-reviews@lists.linux.dev"
<sashiko-reviews@lists.linux.dev>,
"hao_zhang_kdev@163.com" <hao_zhang_kdev@163.com>
Cc: "kvm@vger.kernel.org" <kvm@vger.kernel.org>
Subject: Re: [PATCH v5 3/6] KVM: x86: ioapic: Preserve irr_delivered for duplicate edge interrupts
Date: Thu, 13 Aug 2026 10:10:28 +0000 [thread overview]
Message-ID: <77bb6e42bdbae0bb1ca6584ec87e688db8b7ef9c.camel@intel.com> (raw)
In-Reply-To: <an13sYh4gCyGbMZc@192.168.1.215>
On Thu, 2026-08-13 at 15:52 +0800, Hao Zhang wrote:
> > Could this sequence cause latched edge-triggered interrupts to be silently
> > ignored and lost if a guest temporarily masks IOAPIC pins during interrupt
> > handling?
> >
>
> Sashiko seems to assume that an edge-triggered interrupt which is signaled
> while the IOAPIC RTE is masked must remain latched and then be delivered when
> the RTE is unmasked.
>
> However, the Intel 82093AA I/O Advanced Programmable Interrupt Controller datasheet
> (https://pdos.csail.mit.edu/6.828/2018/readings/ia32/ioapic.pdf) states that
> edge-sensitive interrupts signaled on a masked interrupt pin are ignored,
> i.e. they are not delivered or held pending.
>
> KVM's userspace ABI (https://www.kernel.org/doc/html/v6.12/virt/kvm/api.html#kvm-irq-line)
> also represents an edge interrupt as a pulse, by asserting the line and then deasserting
> it. If that complete pulse occurs while the RTE is masked, there is no pending edge that
> needs to be delivered on unmask.
+1.
next prev parent reply other threads:[~2026-08-13 10:10 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-12 8:27 [PATCH v5 0/6] KVM: x86: Fix IOAPIC remote_irr and irr_delivered handling Hao Zhang
2026-08-12 8:32 ` [PATCH v5 1/6] KVM: x86: ioapic: Update remote_irr only after successful delivery Hao Zhang
2026-08-12 8:34 ` [PATCH v5 2/6] KVM: selftests: Verify failed IOAPIC delivery preserves state Hao Zhang
2026-08-12 8:35 ` [PATCH v5 3/6] KVM: x86: ioapic: Preserve irr_delivered for duplicate edge interrupts Hao Zhang
2026-08-12 8:52 ` sashiko-bot
2026-08-13 7:52 ` Hao Zhang
2026-08-13 10:10 ` Huang, Kai [this message]
2026-08-12 8:37 ` [PATCH v5 4/6] KVM: selftests: Verify duplicate edge preserves IOAPIC state Hao Zhang
2026-08-12 8:39 ` [PATCH v5 5/6] KVM: x86: ioapic: Clear irr_delivered on level-triggered RTE Hao Zhang
2026-08-12 22:41 ` Huang, Kai
2026-08-12 8:41 ` [PATCH v5 6/6] KVM: selftests: Verify edge-to-level clears IOAPIC state Hao Zhang
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