From: David Laight <David.Laight@ACULAB.COM>
To: "'Kirill A. Shutemov'" <kirill@shutemov.name>,
Tom Lendacky <thomas.lendacky@amd.com>
Cc: 'Wu Zongyong' <wuzongyong@linux.alibaba.com>,
"kirill.shutemov@linux.intel.com"
<kirill.shutemov@linux.intel.com>,
"tglx@linutronix.de" <tglx@linutronix.de>,
"mingo@redhat.com" <mingo@redhat.com>,
"dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>,
"x86@kernel.org" <x86@kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"tony.luck@intel.com" <tony.luck@intel.com>,
"wutu.xq2@linux.alibaba.com" <wutu.xq2@linux.alibaba.com>
Subject: RE: [RFC PATCH] x86/insn: support decode MOVSXD instruction for MMIO
Date: Fri, 31 Mar 2023 15:59:44 +0000 [thread overview]
Message-ID: <a6a150f332b44914ac286550b63feab0@AcuMS.aculab.com> (raw)
In-Reply-To: <20230331152508.s7phgif3iozbbpqn@box>
From: Kirill A. Shutemov
> Sent: 31 March 2023 16:25
...
> > No, SEV doesn't support userspace MMIO.
>
> But where do you filter out userspace MMIO? AFAICS, it goes straight from
> from #VC to insn_decode_mmio(). Hm?
Probably by making vm_iomap_memory() fail.
Otherwise MOVSXD is the least of your problems.
You'd need to worry about all the AVX opcodes as well.
Although you might even find kernel code that is using
kernel_fpu_begin/end() to wrap mmio copies that use the
big AVX512 registers.
When each PCIe read takes about 1us (measured into our fpga)
increasing the TLP to 64 bytes (from 8) makes a massive
difference to buffer reads.
(Mostly we try to get the fpga to do writes instead.)
David
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
next prev parent reply other threads:[~2023-03-31 15:59 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-29 2:59 [RFC PATCH] x86/insn: support decode MOVSXD instruction for MMIO Wu Zongyong
2023-03-29 13:49 ` Tom Lendacky
2023-03-30 2:55 ` Wu Zongyong
2023-03-30 12:39 ` kirill.shutemov
2023-03-31 2:24 ` Wu Zongyong
2023-03-31 8:49 ` David Laight
2023-03-31 10:06 ` Kirill A. Shutemov
2023-03-31 13:40 ` Tom Lendacky
2023-03-31 14:09 ` Kirill A. Shutemov
2023-03-31 14:33 ` Tom Lendacky
2023-03-31 15:25 ` Kirill A. Shutemov
2023-03-31 15:50 ` Tom Lendacky
2023-03-31 15:59 ` David Laight [this message]
2023-03-31 15:30 ` Dave Hansen
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