On 05.02.2020 11:24, David Woodhouse wrote: > On Wed, 2020-02-05 at 11:02 +0100, Jan Beulich wrote: >>> + /* Pages from the boot allocator need to pass through >>> init_heap_pages() */ >>> + if ( unlikely(!pg->count_info) ) >> >> ... while I think this check may be fine here, no similar one >> can be used in free_domheap_pages(), yet pages getting handed >> there isn't less likely than ones getting handed to >> free_xenheap_pages() (if we already fear mismatch). > > Do we care about that? > > ICBW but I don't think I've seen a case where boot-allocated pages get > handed to free_domheap_pages() later. I've only seen them handed to > free_xenheap_pages(). These are pages which are mapped to Xen, not > domheap pages. > > You are already expected *not* to conflate free_xenheap_pages() and > free_domheap_pages().
That's the case now, but with us wanting to get rid of the direct map, to sole difference will be whether a mapping gets established. There'll likely be no need for a PGC_xen_heap flag anymore, as we don't need to tell apart the underlying pages (at least as far as the allocator is concerned). > I think it should be OK to declare that freeing boot-allocated pages > with free_xenheap_pages() is permitted, but freeing them with > free_domheap_pages() isn't. I don't think this is going to be a good idea. free_xenheap_pages() right now expects an address within the direct map to be passed. alloc_boot_pages(), however, returns an MFN, which may get mapped to arbitrary linear addresses (or none at all). There's quite a bit more similarity to alloc_domheap_pages(), as that returns struct page_info *, which in turn has a reliable translation to/from MFN. Yet, as you say elsewhere, whether an MFN has an entry in frame_table[] is entirely unclear, so permitting boot- allocator pages to be freed via alloc_domheap_pages() nevertheless still doesn't look any better an idea to me. Jan _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
