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Re: [Xen-devel] [PATCH v4 06/15] domctl: Add XEN_DOMCTL_acpi_access
On 12/02/2016 02:48 AM, Jan Beulich wrote:
On 01.12.16 at 17:43, <boris.ostrovsky@xxxxxxxxxx> wrote:
On 12/01/2016 11:06 AM, Jan Beulich wrote:
+++ b/xen/include/public/domctl.h
@@ -1144,6 +1144,29 @@ struct xen_domctl_psr_cat_op {
typedef struct xen_domctl_psr_cat_op xen_domctl_psr_cat_op_t;
DEFINE_XEN_GUEST_HANDLE(xen_domctl_psr_cat_op_t);
+/* ACPI Generic Address Structure */
+typedef struct gas {
xen_acpi_gas
+#define XEN_ACPI_SYSTEM_MEMORY 0
+#define XEN_ACPI_SYSTEM_IO 1
+ uint8_t space_id; /* Address space */
+ uint8_t bit_width; /* Size in bits of given register */
+ uint8_t bit_offset; /* Bit offset within the register */
+ uint8_t access_width; /* Minimum Access size (ACPI 3.0) */
+ uint64_t address; /* 64-bit address of register */
uint64_aligned_t with explicit padding added ahead of it.
And then there's the question of what uses of this will look like:
I'm not convinced we need to stick to the exact ACPI layout
here, unless you expect (or could imagine) for the tool stack to
hold GAS structures coming from elsewhere in its hands. If we
don't follow the layout as strictly, we could namely widen
bit_width (and maybe bit_offset) to allow for larger transfers
in one go. And in such a relaxed model I don't think we'd need
access_width at all as a field.
There is indeed no current need to use actual ACPI GAS layout but then
it's not GAS, really, and should be named something else.
Which of course is fine by me; I had referred to that structure only
for the underlying principle of specifying how to access the data.
Are there any registers that are not byte-aligned or not whole number of
bytes?
I am thinking about dropping bit_offset (along with access_width) and
making bit_width (byte_)width. And keeping the latter as uint8_t will
also implicitly limit register size to 256 bytes which I think is a
reasonable size limit.
-boris
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