On Thu, Feb 21, 2013 at 04:34:06PM -0800, H. Peter Anvin wrote: > Hi Linus, > > This is a huge set of several partly interrelated (and concurrently > developed) changes, which is why the branch history is messier than > one would like. > > The *really* big items are two humonguous patchsets mostly developed > by Yinghai Lu at my request, which completely revamps the way we > create initial page tables. In particular, rather than estimating how > much memory we will need for page tables and then build them into that > memory -- a calculation that has shown to be incredibly fragile -- we > now build them (on 64 bits) with the aid of a "pseudo-linear mode" -- > a #PF handler which creates temporary page tables on demand. > > This has several advantages: > > 1. It makes it much easier to support things that need access to > data very early (a followon patchset uses this to load microcode > way early in the kernel startup). > > 2. It allows the kernel and all the kernel data objects to be invoked > from above the 4 GB limit. This allows kdump to work on very large > systems. > > 3. It greatly reduces the difference between Xen and native (Xen's > equivalent of the #PF handler are the temporary page tables created > by the domain builder), eliminating a bunch of fragile hooks. > > The patch series also gets us a bit closer to W^X. > > Additional work in this pull is the 64-bit get_user() work which you > were also involved with, and a bunch of cleanups/speedups to > __phys_addr()/__pa(). Looking at figuring out which of the patches in the branch did this, but with this merge I am getting a crash with a very simple PV guest (booted with one 1G): Call Trace: [<ffffffff8103feba>] xen_get_user_pgd+0x5a <-- [<ffffffff8103feba>] xen_get_user_pgd+0x5a [<ffffffff81042d27>] xen_write_cr3+0x77 [<ffffffff81ad2d21>] init_mem_mapping+0x1f9 [<ffffffff81ac293f>] setup_arch+0x742 [<ffffffff81666d71>] printk+0x48 [<ffffffff81abcd62>] start_kernel+0x90 [<ffffffff8109416b>] __add_preferred_console.clone.1+0x9b [<ffffffff81abc5f7>] x86_64_start_reservations+0x2a [<ffffffff81abf0c7>] xen_start_kernel+0x564 And the hypervisor says: (XEN) d7:v0: unhandled page fault (ec=0000) (XEN) Pagetable walk from ffffea000005b2d0: (XEN) L4[0x1d4] = 0000000000000000 ffffffffffffffff (XEN) domain_crash_sync called from entry.S (XEN) Domain 7 (vcpu#0) crashed on cpu#3: (XEN) ----[ Xen-4.2.0 x86_64 debug=n Not tainted ]---- (XEN) CPU: 3 (XEN) RIP: e033:[<ffffffff8103feba>] (XEN) RFLAGS: 0000000000000206 EM: 1 CONTEXT: pv guest (XEN) rax: ffffea0000000000 rbx: 0000000001a0c000 rcx: 0000000080000000 (XEN) rdx: 000000000005b2a0 rsi: 0000000001a0c000 rdi: 0000000000000000 (XEN) rbp: ffffffff81a01dd8 rsp: ffffffff81a01d90 r8: 0000000000000000 (XEN) r9: 0000000010000001 r10: 0000000000000000 r11: 0000000000000000 (XEN) r12: 0000000000000000 r13: 0000001000000000 r14: 0000000000000000 (XEN) r15: 0000000000100000 cr0: 000000008005003b cr4: 00000000000406f0 (XEN) cr3: 0000000411165000 cr2: ffffea000005b2d0 (XEN) ds: 0000 es: 0000 fs: 0000 gs: 0000 ss: e02b cs: e033 (XEN) Guest stack trace from rsp=ffffffff81a01d90: (XEN) 0000000080000000 0000000000000000 0000000000000000 ffffffff8103feba (XEN) 000000010000e030 0000000000010006 ffffffff81a01dd8 000000000000e02b What is bizzare is that I do recall testing this (and Stefano also did it). So I am not sure what has altered.
