On 25/03/2020 15:00, Jan Beulich wrote:
On 22.03.2020 17:14, jul...@xen.org wrote:
From: Julien Grall <jgr...@amazon.com>
It is getting incredibly difficult to use typesafe GFN/MFN/PFN in the
headers because of circular dependency. For instance, asm-x86/page.h
cannot include xen/mm.h.
In order to convert more code to use typesafe, the types are now moved
in a separate header that requires only a few dependencies.
We definitely need to do this, so thanks for investing the
time. I think though that we want to settle up front (and
perhaps record in a comment in the new header) what is or
is not suitable to go into the new header. After all you're
moving not just type definitions, but also simple helper
I am expecting headers to use the typesafe helpers (such mfn_add) in the
long term. So I would like the new header to contain the type
definitions and any wrappers that would turn 'generic' operations safe.
I am not entirely sure yet how to formalize the rules in the header. Any
@@ -1,50 +1,7 @@
- * Definitions for memory pages, frame numbers, addresses, allocations, etc.
* Copyright (c) 2002-2006, K A Fraser <k...@xensource.com>
- * +---------------------+
- * Xen Memory Management
- * +---------------------+
- * Xen has to handle many different address spaces. It is important not to
- * get these spaces mixed up. The following is a consistent terminology which
- * should be adhered to.
- * mfn: Machine Frame Number
- * The values Xen puts into its own pagetables. This is the host physical
- * memory address space with RAM, MMIO etc.
- * gfn: Guest Frame Number
- * The values a guest puts in its own pagetables. For an auto-translated
- * guest (hardware assisted with 2nd stage translation, or shadowed), gfn !=
- * mfn. For a non-translated guest which is aware of Xen, gfn == mfn.
- * pfn: Pseudophysical Frame Number
- * A linear idea of a guest physical address space. For an auto-translated
- * guest, pfn == gfn while for a non-translated guest, pfn != gfn.
- * dfn: Device DMA Frame Number (definitions in include/xen/iommu.h)
- * The linear frame numbers of device DMA address space. All initiators for
- * (i.e. all devices assigned to) a guest share a single DMA address space
- * and, by default, Xen will ensure dfn == pfn.
- * WARNING: Some of these terms have changed over time while others have been
- * used inconsistently, meaning that a lot of existing code does not match the
- * definitions above. New code should use these terms as described here, and
- * over time older code should be corrected to be consistent.
- * An incomplete list of larger work area:
- * - Phase out the use of 'pfn' from the x86 pagetable code. Callers should
- * know explicitly whether they are talking about mfns or gfns.
- * - Phase out the use of 'pfn' from the ARM mm code. A cursory glance
- * suggests that 'mfn' and 'pfn' are currently used interchangeably, where
- * 'mfn' is the appropriate term to use.
- * - Phase out the use of gpfn/gmfn where pfn/mfn are meant. This excludes
- * the x86 shadow code, which uses gmfn/smfn pairs with different,
- * documented, meanings.
@@ -54,100 +11,11 @@
Is there anything left in the header here which requires the
explicit inclusion of xen/kernel.h?
The header was introduced for the sole purpose of the typesafe version
of the min/max helpers. So it should be possible to drop the include.
I will have a look and remove it if we can.