Re: [Xen-devel] RE: [PATCH 5/7] xen/acpi: Domain0 acpi parser related platform hypercall

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Wed, Sep 07, 2011 at 03:06:59PM -0400, Konrad Rzeszutek Wilk wrote:
> > > >> +#define XENPF_enter_acpi_sleep    51
> > > >> +struct xenpf_enter_acpi_sleep {
> > > >> +      /* IN variables */
> > > >> +      uint16_t pm1a_cnt_val;      /* PM1a control value. */
> > > >> +      uint16_t pm1b_cnt_val;      /* PM1b control value. */
> > > > These are uint32_t in native Linux--why truncate in the API and not at 
> > > > use?
> > > 
> > > Does ACPI define them as 32 or 16 bit?
> > 
> > The spec indicates that the length is variable and could be up to 32 bits 
> > (AFAICT).  And Linux uses 32b, which your other patch is truncating for 
> > this call.
> 
> Yikes! Well, looks like we need to fix the Xen ABI too. Lets get that fixed
> and also address all the other comments (thanks for looking at it) you pointed
> out.

So read up the ACPI spec and it says that the minimum is 2 bytes and does not
say anything about the maximum. The list of what the bits do stops at 16-bits
(the last two are reserved) so I think we are actually OK.

Albeit if the spec starts using more of them - then yes we will need to revist
this Xen ABI and potentially add a new call.

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