From: Christoph Hellwig <hch@infradead.org>
To: Robin Murphy <robin.murphy@arm.com>
Cc: Yu Zhao <yuzhao@google.com>,
dongli.zhang@oracle.com, ak@linux.intel.com,
akpm@linux-foundation.org, alexander.sverdlin@nokia.com,
andi.kleen@intel.com, bp@alien8.de, bp@suse.de,
cminyard@mvista.com, corbet@lwn.net,
damien.lemoal@opensource.wdc.com, dave.hansen@linux.intel.com,
hch@infradead.org, iommu@lists.linux-foundation.org,
joe.jin@oracle.com, joe@perches.com, keescook@chromium.org,
kirill.shutemov@intel.com, kys@microsoft.com,
linux-doc@vger.kernel.org, linux-hyperv@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-mips@vger.kernel.org,
ltykernel@gmail.com, michael.h.kelley@microsoft.com,
mingo@redhat.com, m.szyprowski@samsung.com,
parri.andrea@gmail.com, paulmck@kernel.org, pmladek@suse.com,
rdunlap@infradead.org, tglx@linutronix.de,
thomas.lendacky@amd.com, Tianyu.Lan@microsoft.com,
tsbogend@alpha.franken.de, vkuznets@redhat.com,
wei.liu@kernel.org, x86@kernel.org
Subject: Re: [PATCH v1 4/4] swiotlb: panic if nslabs is too small
Date: Mon, 22 Aug 2022 04:26:47 -0700 [thread overview]
Message-ID: <YwNn92WP3rP4ylZu@infradead.org> (raw)
In-Reply-To: <f8c743d8-fcbe-4ef7-5f86-d63086552ffd@arm.com>
On Mon, Aug 22, 2022 at 10:49:09AM +0100, Robin Murphy wrote:
> Hmm, it's possible this might be quietly fixed by 20347fca71a3, but either
> way I'm not sure why we would need to panic *before* we've even tried to
> allocate anything, when we could simply return with no harm done? If we've
> ended up calculating (or being told) a buffer size which is too small to be
> usable, that should be no different to disabling SWIOTLB entirely.
Hmm. I think this might be a philosophical question, but I think
failing the boot with a clear error report for a configuration that is
supposed to work but can't is way better than just panicing later on.
> Historically, passing "swiotlb=1" on the command line has been used to save
> memory when the user knows SWIOTLB isn't needed. That should definitely not
> be allowed to start panicking.
I've never seen swiotlb=1 advertized as a way to disable swiotlb.
That's always been swiotlb=noforce, which cleanly disables it.
next prev parent reply other threads:[~2022-08-22 11:27 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20220611082514.37112-5-dongli.zhang@oracle.com>
2022-08-20 1:20 ` [PATCH v1 4/4] swiotlb: panic if nslabs is too small Yu Zhao
2022-08-22 9:49 ` Robin Murphy
2022-08-22 11:26 ` Christoph Hellwig [this message]
2022-08-22 12:32 ` Robin Murphy
2022-08-22 22:27 ` Dongli Zhang
2022-08-22 23:10 ` Yu Zhao
2022-08-22 23:47 ` Dongli Zhang
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