Date: Mon, 24 Dec 2018 11:28:37 +0800 From: =?UTF-8?B?5a6L6L6w5Lyf?= <scwsy00@gmail.com> To: freebsd-questions@freebsd.org Subject: Re: How to access physical memory Message-ID: <CABsV5RzE8JiOOBA408XXenuLFBwgLAtB5PDMQT7o_8mEkAxU=A@mail.gmail.com> In-Reply-To: <CABsV5RwodOK18HRE%2BDj7BNNQWw9O45ynixabij2Dg_CWDO9YFA@mail.gmail.com> References: <CABsV5RwodOK18HRE%2BDj7BNNQWw9O45ynixabij2Dg_CWDO9YFA@mail.gmail.com>
next in thread | previous in thread | raw e-mail | index | archive | help
``` pdp = (pdp_entry_t *)PHYS_TO_DMAP(*pml4 & PG_FRAME); /* Now find the pdp page */ pdp = &pdp[pdpindex & ((1ul << NPDPEPGSHIFT) - 1)]; *pdp = VM_PAGE_TO_PHYS(m) | PG_U | PG_RW | PG_V | PG_A | PG_M; ``` There is the code in _pmap_allocpte. 宋辰伟 <scwsy00@gmail.com> 于2018年12月24日周一 上午11:23写道： > Hi I'm the new here . And I have some questions with pmap. > > [image: 1545542790461.png] > > > See `*pml4` is the physical address of a page with some flag. And then > updated the address to the Direct Map Space. Then We calculate the offset > of the real pdp we need . > > How could it access to `*pdp`? it is a virtual addr in Direct Map Space. > Why don't change the physical space directly since we have the physical > page already. >
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?CABsV5RzE8JiOOBA408XXenuLFBwgLAtB5PDMQT7o_8mEkAxU=A>