On Fri, Mar 31, 2023 at 08:49:48AM +0000, David Laight wrote:
From: Wu Zongyong
Sent: 31 March 2023 03:24
On Thu, Mar 30, 2023 at 03:39:51PM +0300, kirill.shutemov@xxxxxxxxxxxxxxx wrote:
On Wed, Mar 29, 2023 at 10:59:37AM +0800, Wu Zongyong wrote:To be honest, I don't find a specific user which uses the MOVSXD.
It seems MOVSXD which opcode is 0x63 is not handled, support
to decode it in insn_decode_mmio().
Do you have a particular user in mind?
But both Intel and AMD's instructions reference contains MOVSXD and lots
of MOVSXD instructions occur when I "objdump -S vmlinux", so I think it
may be useful to support it in insn_decode_mmio().
Are there some special consideration about this instruction?
It is a sign-extending memory read (32bit to 64bit).
You pretty much never want to do that to a device register.
Also kernel code should be using readl() (etc) which do
unsigned reads.
So they should never happen for mmio.
Of course, if you mmap() PCIe space directly into a program's
address space anything might happen ...
There are two users of the interface: TDX and SEV. TDX doesn't allow
userspace MMIO. SEV *seems* allows it, but I am not sure how it is safe.
Tom?