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From: David Vrabel <dvrabel@cantab.net>
To: "Marek Marczykowski-Górecki" <marmarek@invisiblethingslab.com>,
	linux-kernel@vger.kernel.org
Cc: Juergen Gross <jgross@suse.com>,
	Stefano Stabellini <sstabellini@kernel.org>,
	Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>,
	Jan Beulich <jbeulich@suse.com>,
	"moderated list:XEN HYPERVISOR INTERFACE" 
	<xen-devel@lists.xenproject.org>
Subject: Re: [PATCH] xen-pciback: Consider MSI-X enabled only when MASKALL bit is cleared
Date: Thu, 17 Nov 2022 12:54:51 +0000	[thread overview]
Message-ID: <0afe3f35-1b25-d1c6-89bb-8dae7a4070e9@cantab.net> (raw)
In-Reply-To: <20221117114122.1588338-1-marmarek@invisiblethingslab.com>

On 17/11/2022 11:41, Marek Marczykowski-Górecki wrote:
> Linux enables MSI-X before disabling INTx, but keeps MSI-X masked until
> the table is filled. Then it disables INTx just before clearing MASKALL
> bit. Currently this approach is rejected by xen-pciback.
> Allow setting PCI_MSIX_FLAGS_ENABLE while INTx is still enabled as long
> as PCI_MSIX_FLAGS_MASKALL is set too.

The use of MSI-X interrupts is conditional on only the MSI-X Enable bit. 
Setting MSI-X Enable effectively overrides the Interrupt Disable bit in 
the Command register.

PCIe 6.0.1 section 7.7.2.2. "MSI-X Enable ... is prohibited from using 
INTx interrupts (if implemented)." And there is similar wording for MSI 
Enable.

I think you need to shuffle the checks for MSI/MSI-X in 
xen_pcibk_get_interrupt_type() so they are _before_ the check of the 
Interrupt Disable bit in the Command register.

David

  parent reply	other threads:[~2022-11-17 13:10 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-11-17 11:41 Marek Marczykowski-Górecki
2022-11-17 12:28 ` Andrew Cooper
2022-11-17 13:43   ` Jan Beulich
2022-11-17 12:54 ` David Vrabel [this message]
2022-11-17 13:13   ` Marek Marczykowski-Górecki
2022-11-17 13:33     ` Jan Beulich
2022-11-17 14:32       ` Marek Marczykowski-Górecki
2022-11-17 13:50 ` Jan Beulich

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