From: Ashish Kalra <ashish.kalra@amd.com>
To: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Thomas.Lendacky@amd.com, brijesh.singh@amd.com,
dave.hansen@linux-intel.com, peterz@infradead.org,
x86@kernel.org, linux-kernel@vger.kernel.org,
iommu@lists.linux-foundation.org, mingo@redhat.com, bp@alien8.de,
luto@kernel.org, hpa@zytor.com,
Konrad Rzeszutek Wilk <konrad@darnok.org>,
tglx@linutronix.de, hch@lst.de
Subject: Re: [PATCH v2] swiotlb: Adjust SWIOTBL bounce buffer size for SEV guests.
Date: Fri, 24 Jan 2020 23:00:08 +0000 [thread overview]
Message-ID: <20200124230008.GA1565@ashkalra_ubuntu_server> (raw)
In-Reply-To: <20200121205403.GC75374@Konrads-MacBook-Pro.local>
On Tue, Jan 21, 2020 at 03:54:03PM -0500, Konrad Rzeszutek Wilk wrote:
> >
> > Additional memory calculations based on # of PCI devices and
> > their memory ranges will make it more complicated with so
> > many other permutations and combinations to explore, it is
> > essential to keep this patch as simple as possible by
> > adjusting the bounce buffer size simply by determining it
> > from the amount of provisioned guest memory.
>>
>> Please rework the patch to:
>>
>> - Use a log solution instead of the multiplication.
>> Feel free to cap it at a sensible value.
Ok.
>>
>> - Also the code depends on SWIOTLB calling in to the
>> adjust_swiotlb_default_size which looks wrong.
>>
>> You should not adjust io_tlb_nslabs from swiotlb_size_or_default.
>> That function's purpose is to report a value.
>>
>> - Make io_tlb_nslabs be visible outside of the SWIOTLB code.
>>
>> - Can you utilize the IOMMU_INIT APIs and have your own detect which would
>> modify the io_tlb_nslabs (and set swiotbl=1?).
This seems to be a nice option, but then IOMMU_INIT APIs are
x86-specific and this swiotlb buffer size adjustment is also needed
for other memory encryption architectures like Power, S390, etc.
>>
>> Actually you seem to be piggybacking on pci_swiotlb_detect_4gb - so
>> perhaps add in this code ? Albeit it really should be in it's own
>> file, not in arch/x86/kernel/pci-swiotlb.c
Actually, we piggyback on pci_swiotlb_detect_override which sets
swiotlb=1 as x86_64_start_kernel() and invocation of sme_early_init()
forces swiotlb on, but again this is all x86 architecture specific.
Thanks,
Ashish
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next prev parent reply other threads:[~2020-01-25 1:31 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-09 23:13 [PATCH v2] swiotlb: Adjust SWIOTBL bounce buffer size for SEV guests Ashish Kalra
2019-12-20 1:52 ` Konrad Rzeszutek Wilk
2020-01-21 20:09 ` Ashish Kalra
2020-01-21 20:54 ` Konrad Rzeszutek Wilk
2020-01-24 23:00 ` Ashish Kalra [this message]
2020-02-04 19:35 ` Ashish Kalra
2020-03-03 17:03 ` Konrad Rzeszutek Wilk
2020-03-12 0:43 ` Ashish Kalra
2020-03-30 22:25 ` Ashish Kalra
2020-04-27 18:53 ` Ashish Kalra
2020-06-23 13:38 ` Konrad Rzeszutek Wilk
2020-06-24 0:23 ` Ashish Kalra
2020-06-24 7:05 ` Ashish Kalra
2020-06-24 21:11 ` Konrad Rzeszutek Wilk
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