Re: [Xen-devel] [PATCH v4 4/8] monitor: ARM SMC events

[Julien Grall <julien.grall@xxxxxxx>]

On 04/07/2016 20:13, Tamas K Lengyel wrote:
> > On ARMv8, ESR_EL2.ISS has a different encoding depending on the state (i.e
> > AArch64 or AArch32). See D7-1861 in ARM DDI 0487A.i. Furthermore, in AArch32
> > state, the ARMv8 specs permits to trap conditional SMC instructions that
> > fail their condition check (see D7-1897 in ARM DDI 0406C.c).
> Hi Julien,
Hello Tamas,

> I'm unable to find the reference you mention about conditional SMCs
> generating Hyp traps even if they fail their condition checks on
> certain implementations. The only references I find in ARMv8 manual
> states explicitly that "The trap that HCR_EL2.TSC enables traps the
> attempted execution of a conditional SMC instruction only if the
> instruction passes its condition code check" (D1.15) and "The
> architecture requires that a Hyp trap on a conditional SMC instruction
> generates an exception only if the instruction passes its condition
> code check, see Trapping use of the SMC instruction on page G1-3510"
> (G1.16).
If you look at description of HCR_EL2.TSC at D7-1973 in DDI 0487A.j;
"In AArch32 state, the ARMv8-A architecture permits, but does not 
require, this trap to apply to conditional SMC instructions that fail 
their condition code check, in the same way as with traps on
other conditional instructions."

AFAICT the change was already present in the ARM ARM beginning of 2015. 
So I suspect you are using an old version of the spec. In general, I 
would recommend you to use the most recent spec for your development.
For future question related to the spec, please mention the version of 
the spec you quote. It makes easier to find out what is going on.
Regards,

--
Julien Grall

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