On Sat, 2007-10-13 at 16:17 +0200, J. Mayer wrote: > On Sat, 2007-10-13 at 16:07 +0300, Blue Swirl wrote: > > On 10/13/07, J. Mayer wrote: > > > On Sat, 2007-10-13 at 13:47 +0300, Blue Swirl wrote: > > > > On 10/13/07, J. Mayer wrote: > > > > > The problem: > > > > > some CPU architectures, namely PowerPC and maybe others, offers > > > > > facilities to access the memory or I/O in the reverse endianness, ie > > > > > little-endian instead of big-endian for PowerPC, or provide instruction > > > > > to make memory accesses in the "reverse-endian". This is implemented as > > > > > a global flag on some CPU. This case is already handled by the PowerPC > > > > > emulation but is is far from being optimal. Some other implementations > > > > > allow the OS to store an "reverse-endian" flag in the TLB or the segment > > > > > descriptors, thus providing per-page or per-segment endianness control. > > > > > This is mostly used to ease driver migration from a PC platform to > > > > > PowerPC without taking any care of the device endianness in the driver > > > > > code (yes, this is bad...). > > > > > > > > Nice, this may be useful for Sparc64. It has a global CPU flag for > > > > endianness, individual pages can be marked as reverse endian, and > > > > finally there are instructions that access memory in reverse endian. > > > > The end result is a XOR of all these reverses. Though I don't know if > > > > any of these features are used at all. > > > > > > I realized that I/O accesses for reverse-endian pages were not correct > > > in the softmmu_template.h header. This new version fixes this. It also > > > remove duplicated code in the case of unaligned accesses in a > > > reverse-endian page. > > > > I think 64 bit access case is not handled correctly, but to solve that > > it would be nice to extend the current IO access system to 64 bits. > > I think that if it was previously correct, it should still be, but... I > don't know how much having 64 bits I/O accesses is interresting, as I > don't know if there are real hw buses that have 64 bits data path... > > Here's another version taking care of your remark about ldl memory > accessors. > * I replaced all ldl occurences with ldul > * when TARGET_LONG_BITS == 64, I also added ldsl accessors. And I > started using it in the PowerPC memory access micro-ops. > Then the patch is really more invasive than the previous ones. > This still does not break PowerPC or i386 target, as it seems. Here's a new version. The only change is that, for consistency, I did add the big-endian and little-endian accessors that were documented in cpu-all.h as unimplemented. The implementation is quite trivial, having native and reverse-endian accessors available, and changes functionnally nothing to the previous version. -- J. Mayer Never organized