[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH] xen: add a comment for hypercall_xlat_continuation
# HG changeset patch # User Ian Campbell <ian.campbell@xxxxxxxxxx> # Date 1320911800 0 # Node ID 3c6eaf62996dd26d7d0a055955d30bc6c7067f91 # Parent e6af32ecb4483457d5ad9a7b674c18aaf20cc085 xen: add a comment for hypercall_xlat_continuation The interface of this function is really rather complex and having reverse engineered it for the N'th time I think it is time to write things down. Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx> diff -r e6af32ecb448 -r 3c6eaf62996d xen/include/xen/compat.h --- a/xen/include/xen/compat.h Tue Oct 18 14:15:09 2011 +0100 +++ b/xen/include/xen/compat.h Thu Nov 10 07:56:40 2011 +0000 @@ -185,6 +185,34 @@ static inline int name(k xen_ ## n *x, k CHECK_FIELD_COMMON_(k, CHECK_NAME_(k, n ## __ ## f1 ## __ ## f2 ## __ ## \ f3, F2), n, f1.f2.f3) +/* + * Translate a native continuation into a compat guest continuation. + * + * id: If non-NULL then points to an integer N between 0-5. Will be updated + * with the value of the N'th argument to the hypercall. The N'th argument must + * not be subject to translation (i.e. cannot be referenced by @mask below). + * This option is useful for extracting the "op" argument or similar from the + * hypercall to enable further xlat processing. + * + * mask: Specifies which of the hypercall arguments require compat translation. + * bit 0 indicates that the 0'th argument requires translation, bit 1 indicates + * that the first argument requires translation and so on. Native and compat + * values for each translated argument are provided as @varargs (see below). + * + * varargs: For each bit which is set in @mask the varargs contain a native + * value (unsigned long) and a compat value (unsigned int). If the native value + * and compat value differ and the N'th argument is equal to the native value + * then that argument is replaced by the compat value. If the native and compat + * values are equal then no translation takes place. If the N'th argument does + * not equal the native value then no translation takes place. + * + * Any untranslated argument (whether due to not being requested in @mask, + * native and compat values being equal or N'th argument not equalling native + * value) must be equal in both native and compat representations (i.e. the + * native version cannot have any bits > 32 set) + * + * Return: Number of arguments which were actually translated. + */ int hypercall_xlat_continuation(unsigned int *id, unsigned int mask, ...); /* In-place translation functons: */ _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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