Hi Julien, > -----Original Message----- > From: Julien Grall <jul...@xen.org> > Sent: Wednesday, April 21, 2021 5:04 PM > To: Henry Wang <henry.w...@arm.com>; sstabell...@kernel.org; xen- > de...@lists.xenproject.org > Cc: Wei Chen <wei.c...@arm.com>; Penny Zheng > <penny.zh...@arm.com>; Bertrand Marquis <bertrand.marq...@arm.com> > Subject: Re: Discussion of Xenheap problems on AArch64 > > > > On 21/04/2021 07:28, Henry Wang wrote: > > Hi, > > Hi Henry, > > > > > We are trying to implement the static memory allocation on AArch64. Part > of > > this feature is the reserved heap memory allocation, where a specific range > of > > memory is reserved only for heap. In the development process, we found a > > pitfall in current AArch64 setup_xenheap_mappings() function. > > > > According to a previous discussion in community > > https://lore.kernel.org/xen-devel/20190216134456.10681-1- > peng....@nxp.com/, > > on AArch64, bootmem is initialized after setup_xenheap_mappings(), > > setup_xenheap_mappings() may try to allocate memory before memory > has been > > handed over to the boot allocator. If the reserved heap memory allocation > is > > introduced, either of below 2 cases will trigger a crash: > > > > 1. If the reserved heap memory is at the end of the memory block list and > the > > gap between reserved and unreserved memory is bigger than 512GB, when > we setup > > mappings from the beginning of the memory block list, we will get OOM > caused > > by lack of pages in boot allocator. This is because the memory that is > reserved > > for heap has not been mapped and added to the boot allocator. > > > > 2. If we add the memory that is reserved for heap to boot allocator first, > and > > then setup mappings for banks in the memory block list, we may get a page > which > > has not been setup mapping, causing a data abort. > > There are a few issues with setup_xenheap_mappings(). I have been > reworking the code on my spare time and started to upstream bits of it. > A PoC can be found here: > > https://xenbits.xen.org/gitweb/?p=people/julieng/xen- > unstable.git;a=shortlog;h=refs/heads/pt/dev >
Really great news! Thanks you very much for the information and your hard work on the PoC :) I will start to go through your PoC code then. Kind regards, Henry > Cheers, > > -- > Julien Grall
