Hi Julien, Sorry for the late reply, I kinda missed this email somehow....
Please see my inline reply ^^ > -----Original Message----- > From: Xen-devel <xen-devel-boun...@lists.xenproject.org> On Behalf Of > Julien Grall > Sent: Monday, April 26, 2021 4:20 AM > 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 10:32, Henry Wang wrote: > > Hi Julien, > > Hi Henry, > > >> -----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. > > I spent sometimes today to clean-up the PoC and sent a series on the ML > (see [1]). This has been lightly tested so far. > > Would you be able to give a try and let me know if it helps your problem? Yes of course! I will start to test this series ^^ Thank you for your work! > > For convenience, I have pushed a branch with the series applied here: > > https://xenbits.xen.org/gitweb/?p=people/julieng/xen- > unstable.git;a=shortlog;h=refs/heads/pt/rfc-v2 > Great, thanks! > Cheers, > > [1] https://lore.kernel.org/xen-devel/20210425201318.15447-1- > jul...@xen.org/ > > -- > Julien Grall
