From: Jason Gunthorpe <jgg@ziepe.ca>
To: Manivannan Sadhasivam <mani@kernel.org>
Cc: Bjorn Helgaas <helgaas@kernel.org>,
Manivannan Sadhasivam <manivannan.sadhasivam@oss.qualcomm.com>,
Bjorn Helgaas <bhelgaas@google.com>,
linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org,
iommu@lists.linux.dev, Naresh Kamboju <naresh.kamboju@linaro.org>,
Pavankumar Kondeti <quic_pkondeti@quicinc.com>,
Xingang Wang <wangxingang5@huawei.com>,
Marek Szyprowski <m.szyprowski@samsung.com>,
Robin Murphy <robin.murphy@arm.com>,
Alex Williamson <alex@shazbot.org>,
James Puthukattukaran <james.puthukattukaran@oracle.com>
Subject: Re: [PATCH v3 3/4] PCI: Disable ACS SV capability for the broken IDT switches
Date: Fri, 6 Feb 2026 10:30:14 -0400 [thread overview]
Message-ID: <20260206143014.GH943673@ziepe.ca> (raw)
In-Reply-To: <ga5ro3nvrbmbjubtk6xnozzc6exqq5vnkmp2pfuhtnzmpsuogz@lcycdoxtu2k4>
On Fri, Feb 06, 2026 at 02:41:36PM +0530, Manivannan Sadhasivam wrote:
> > It'd be worth expanding on this and what the effect of avoiding ACS SV
> > is. Does this change which devices can be safely passed through to
> > virtual guests? Does it give up isolation that users expect?
> >
>
> IMO, ACS SV is somewhat broken on this switch. But we can still passthrough the
> downstream devices to the guests. There won't be ACS SV apparently, but that's
> what users will get with broken hw.
I agree with this, the HW is very broken, let's have it at least work
properly in Linux on bare metal out of the box.
If someone really insists they need virtualization with narrow groups
on this HW then they need to come with a more complete fix. Using VFIO
is going to open up the reset flows that are problematic with the
current solution, so it isn't like that is already working fully.
Somehow I suspect nobody would use this switch for virtualization :)
Jason
next prev parent reply other threads:[~2026-02-06 14:30 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-01-02 15:34 [PATCH v3 0/4] PCI: Fix ACS enablement for Root Ports in OF platforms Manivannan Sadhasivam via B4 Relay
2026-01-02 15:34 ` [PATCH v3 1/4] PCI: Enable ACS only after configuring IOMMU for " Manivannan Sadhasivam via B4 Relay
2026-02-04 23:33 ` Bjorn Helgaas
2026-02-06 9:18 ` Manivannan Sadhasivam
2026-02-06 15:37 ` Robin Murphy
2026-04-03 16:45 ` Regression " Jon Kohler
2026-04-03 16:52 ` Manivannan Sadhasivam
2026-04-03 16:47 ` Jon Kohler
2026-01-02 15:34 ` [PATCH v3 2/4] PCI: Cache ACS capabilities Manivannan Sadhasivam via B4 Relay
2026-01-02 15:34 ` [PATCH v3 3/4] PCI: Disable ACS SV capability for the broken IDT switches Manivannan Sadhasivam via B4 Relay
2026-02-05 23:39 ` Bjorn Helgaas
2026-02-06 9:11 ` Manivannan Sadhasivam
2026-02-06 14:30 ` Jason Gunthorpe [this message]
2026-02-06 14:43 ` Robin Murphy
2026-02-06 14:46 ` Bjorn Helgaas
2026-02-06 14:52 ` Jason Gunthorpe
2026-02-06 15:05 ` Bjorn Helgaas
2026-02-06 15:07 ` Jason Gunthorpe
2026-01-02 15:34 ` [PATCH v3 4/4] PCI: Extend the pci_disable_broken_acs_cap() quirk for one more IDT switch Manivannan Sadhasivam via B4 Relay
2026-01-29 17:42 ` [PATCH v3 0/4] PCI: Fix ACS enablement for Root Ports in OF platforms Manivannan Sadhasivam
2026-01-29 18:06 ` Jason Gunthorpe
2026-02-06 18:32 ` Bjorn Helgaas
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