As documented in comments in struct xen_memory_exchange, the input to the hypercall is a set of MFNs which are to be removed from the domain, plus a set of PFNs where the newly allocated MFNs are to appear. Present comment and parameter naming don't correctly reflect that. Signed-off-by: Jan Beulich <jbeulich@suse.com> --- Should "fns_out" maybe be "fns_inout" to further emphasize the dual purpose? --- a/arch/x86/xen/mmu_pv.c +++ b/arch/x86/xen/mmu_pv.c @@ -XXX,XX +XXX,XX @@ static void xen_remap_exchanged_ptes(uns } /* - * Perform the hypercall to exchange a region of our pfns to point to - * memory with the required contiguous alignment. Takes the pfns as - * input, and populates mfns as output. + * Perform the hypercall to exchange a region of our pages to point to memory + * with the required contiguous alignment. Takes as input the mfns to trade + * in and the pfns where the new pages are to appear, and populates mfns as + * output. * * Returns a success code indicating whether the hypervisor was able to * satisfy the request or not. */ static int xen_exchange_memory(unsigned long extents_in, unsigned int order_in, - unsigned long *pfns_in, + unsigned long *mfns_in, unsigned long extents_out, unsigned int order_out, - unsigned long *mfns_out, + unsigned long *fns_out, unsigned int address_bits) { long rc; @@ -XXX,XX +XXX,XX @@ static int xen_exchange_memory(unsigned .in = { .nr_extents = extents_in, .extent_order = order_in, - .extent_start = pfns_in, + .extent_start = mfns_in, .domid = DOMID_SELF }, .out = { .nr_extents = extents_out, .extent_order = order_out, - .extent_start = mfns_out, + .extent_start = fns_out, .address_bits = address_bits, .domid = DOMID_SELF } As documented in comments in struct xen_memory_exchange, the input to the hypercall is a set of MFNs which are to be removed from the domain, plus a set of PFNs where the newly allocated MFNs are to appear. Present comment and parameter naming don't correctly reflect that. Signed-off-by: Jan Beulich <jbeulich@suse.com> Reviewed-by: Juergen Gross <jgross@suse.com> --- v2: "fns_out" => "fns_inout". Mention parameter names in comment. --- a/arch/x86/xen/mmu_pv.c +++ b/arch/x86/xen/mmu_pv.c @@ -XXX,XX +XXX,XX @@ static void xen_remap_exchanged_ptes(uns } /* - * Perform the hypercall to exchange a region of our pfns to point to - * memory with the required contiguous alignment. Takes the pfns as - * input, and populates mfns as output. + * Perform the hypercall to exchange a region of our pages to point to memory + * with the required contiguous alignment. Takes as input the mfns to trade + * in (mfns_in) and the pfns where the new pages are to appear (fns_inout), + * and populates mfns as output (fns_inout). * * Returns a success code indicating whether the hypervisor was able to * satisfy the request or not. */ static int xen_exchange_memory(unsigned long extents_in, unsigned int order_in, - unsigned long *pfns_in, + unsigned long *mfns_in, unsigned long extents_out, unsigned int order_out, - unsigned long *mfns_out, + unsigned long *fns_inout, unsigned int address_bits) { long rc; @@ -XXX,XX +XXX,XX @@ static int xen_exchange_memory(unsigned .in = { .nr_extents = extents_in, .extent_order = order_in, - .extent_start = pfns_in, + .extent_start = mfns_in, .domid = DOMID_SELF }, .out = { .nr_extents = extents_out, .extent_order = order_out, - .extent_start = mfns_out, + .extent_start = fns_inout, .address_bits = address_bits, .domid = DOMID_SELF }