From: "Petr Tesařík" <petr@tesarici.cz>
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: Mon, 22 May 2023 09:54:08 +0200 [thread overview]
Message-ID: <20230522095408.02874498@meshulam.tesarici.cz> (raw)
In-Reply-To: <ZGdLErBzi9MANL3i@mail-itl>
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On Fri, 19 May 2023 12:10:26 +0200
Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com> wrote:
> On Fri, May 19, 2023 at 06:04:05AM +0200, Christoph Hellwig wrote:
> > On Thu, May 18, 2023 at 08:18:39PM +0200, Marek Marczykowski-Górecki wrote:
> > > On Thu, May 18, 2023 at 03:42:51PM +0200, Christoph Hellwig wrote:
> > > > Remove the dangerous late initialization of xen-swiotlb in
> > > > pci_xen_swiotlb_init_late and instead just always initialize
> > > > xen-swiotlb in the boot code if CONFIG_XEN_PCIDEV_FRONTEND is enabled.
> > > >
> > > > Signed-off-by: Christoph Hellwig <hch@lst.de>
> > >
> > > Doesn't it mean all the PV guests will basically waste 64MB of RAM
> > > by default each if they don't really have PCI devices?
> >
> > If CONFIG_XEN_PCIDEV_FRONTEND is enabled, and the kernel's isn't booted
> > with swiotlb=noforce, yes.
>
> That's "a bit" unfortunate, since that might be significant part of the
> VM memory, or if you have a lot of VMs, a significant part of the host
> memory - it quickly adds up.
I wonder if dynamic swiotlb allocation might also help with this...
Petr T
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next prev parent reply other threads:[~2023-05-22 7:56 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
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 [this message]
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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