From: Christoph Hellwig <hch@lst.de>
To: "Marek Marczykowski-Górecki" <marmarek@invisiblethingslab.com>
Cc: Christoph Hellwig <hch@lst.de>, Juergen Gross <jgross@suse.com>,
Stefano Stabellini <sstabellini@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
Ben Skeggs <bskeggs@redhat.com>,
Karol Herbst <kherbst@redhat.com>, Lyude Paul <lyude@redhat.com>,
xen-devel@lists.xenproject.org, iommu@lists.linux.dev,
linux-kernel@vger.kernel.org, nouveau@lists.freedesktop.org
Subject: Re: [PATCH 2/4] x86: always initialize xen-swiotlb when xen-pcifront is enabling
Date: Fri, 19 May 2023 14:41:18 +0200 [thread overview]
Message-ID: <20230519124118.GA5869@lst.de> (raw)
In-Reply-To: <ZGdLErBzi9MANL3i@mail-itl>
On Fri, May 19, 2023 at 12:10:26PM +0200, Marek Marczykowski-Górecki wrote:
> While I would say PCI passthrough is not very common for PV guests, can
> the decision about xen-swiotlb be delayed until you can enumerate
> xenstore to check if there are any PCI devices connected (and not
> allocate xen-swiotlb by default if there are none)? This would
> still not cover the hotplug case (in which case, you'd need to force it
> with a cmdline), but at least you wouldn't loose much memory just
> because one of your VMs may use PCI passthrough (so, you have it enabled
> in your kernel).
How early can we query xenstore? We'd need to do this before setting
up DMA for any device.
The alternative would be to finally merge swiotlb-xen into swiotlb, in
which case we might be able to do this later. Let me see what I can
do there.
next prev parent reply other threads:[~2023-05-19 12:42 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-18 13:42 unexport swiotlb_active Christoph Hellwig
2023-05-18 13:42 ` [PATCH 1/4] x86: move a check out of pci_xen_swiotlb_init Christoph Hellwig
2023-05-18 13:42 ` [PATCH 2/4] x86: always initialize xen-swiotlb when xen-pcifront is enabling Christoph Hellwig
2023-05-18 18:18 ` Marek Marczykowski-Górecki
2023-05-19 4:04 ` Christoph Hellwig
2023-05-19 10:10 ` Marek Marczykowski-Górecki
2023-05-19 12:41 ` Christoph Hellwig [this message]
2023-05-19 12:49 ` Andrew Cooper
2023-05-19 12:58 ` Christoph Hellwig
2023-05-20 6:21 ` Christoph Hellwig
2023-05-22 7:52 ` Petr Tesařík
2023-05-22 7:54 ` Petr Tesařík
2023-05-22 8:37 ` Juergen Gross
2023-06-07 13:12 ` Christoph Hellwig
2023-06-09 15:38 ` Juergen Gross
2023-06-12 6:47 ` Christoph Hellwig
2023-06-12 8:08 ` Juergen Gross
2023-06-12 8:23 ` Christoph Hellwig
2023-05-18 13:42 ` [PATCH 3/4] drm/nouveau: stop using is_swiotlb_active Christoph Hellwig
2023-05-18 20:30 ` Lyude Paul
2023-06-07 13:11 ` Christoph Hellwig
2023-05-18 13:42 ` [PATCH 4/4] swiotlb: unexport is_swiotlb_active Christoph Hellwig
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