From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wei Liu Subject: Re: [PATCH] minios: don't rely on specific page table allocation scheme Date: Fri, 20 Nov 2015 12:46:25 +0000 Message-ID: <20151120124625.GX1495@citrix.com> References: <1447949116-9543-1-git-send-email-jgross@suse.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <1447949116-9543-1-git-send-email-jgross@suse.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Juergen Gross Cc: wei.liu2@citrix.com, Ian.Campbell@citrix.com, stefano.stabellini@eu.citrix.com, ian.jackson@eu.citrix.com, xen-devel@lists.xen.org, samuel.thibault@ens-lyon.org List-Id: xen-devel@lists.xenproject.org On Thu, Nov 19, 2015 at 05:05:16PM +0100, Juergen Gross wrote: > Today mini-os is making assumptions how the page tables it is started > with are being allocated. Especially it is using the number of page > table frames to calculate which is the first unmapped pfn. > > Instead of relying on page table number assumptions just look into the > page tables to find the first pfn not already mapped. > > Signed-off-by: Juergen Gross I ran both pv-grub-x86_{64,32} up to the point when grub menu was shown -- That's beyond the point of the original crash. I also ran mini-os 32 and 64 bit with this patch on toolstack without large p2m series. They worked. > --- > arch/x86/mm.c | 47 ++++++++++++++++++++++++++++++++++++----------- > include/x86/arch_mm.h | 7 ------- > 2 files changed, 36 insertions(+), 18 deletions(-) > > diff --git a/arch/x86/mm.c b/arch/x86/mm.c > index 9c6d1b8..5d7c006 100644 > --- a/arch/x86/mm.c > +++ b/arch/x86/mm.c > @@ -200,8 +200,8 @@ static void build_pagetable(unsigned long *start_pfn, unsigned long *max_pfn) > int count = 0; > int rc; > > - pfn_to_map = > - (start_info.nr_pt_frames - NOT_L1_FRAMES) * L1_PAGETABLE_ENTRIES; > + pfn_to_map = (*start_pfn + L1_PAGETABLE_ENTRIES - 1) & > + ~(L1_PAGETABLE_ENTRIES - 1); > > if ( *max_pfn >= virt_to_pfn(HYPERVISOR_VIRT_START) ) > { > @@ -229,9 +229,15 @@ static void build_pagetable(unsigned long *start_pfn, unsigned long *max_pfn) > #if defined(__x86_64__) > offset = l4_table_offset(start_address); > /* Need new L3 pt frame */ > - if ( !(start_address & L3_MASK) ) > - if ( need_pt_frame(start_address, L3_FRAME) ) > - new_pt_frame(&pt_pfn, pt_mfn, offset, L3_FRAME); > + if ( !(tab[offset] & _PAGE_PRESENT) ) > + { > + if ( !need_pt_frame(start_address, L3_FRAME) ) > + { > + printk("ERROR: build_pagetable(): L3 frame not present\n"); > + do_exit(); > + } > + new_pt_frame(&pt_pfn, pt_mfn, offset, L3_FRAME); I'm not sure about this hunk and other similar hunks. Shouldn't this be if ( need_pt_frame(start_address, L3_FRAME) ) new_pt_frame(&pt_pfn, pt_mfn, offset, L3_FRAME); That is, just like before. Wei.