| From foo@baz Sun Jun 17 12:07:34 CEST 2018 |
| From: "van der Linden, Frank" <fllinden@amazon.com> |
| Date: Fri, 4 May 2018 16:11:00 -0400 |
| Subject: x86/xen: Reset VCPU0 info pointer after shared_info remap |
| |
| From: "van der Linden, Frank" <fllinden@amazon.com> |
| |
| [ Upstream commit d1ecfa9d1f402366b1776fbf84e635678a51414f ] |
| |
| This patch fixes crashes during boot for HVM guests on older (pre HVM |
| vector callback) Xen versions. Without this, current kernels will always |
| fail to boot on those Xen versions. |
| |
| Sample stack trace: |
| |
| BUG: unable to handle kernel paging request at ffffffffff200000 |
| IP: __xen_evtchn_do_upcall+0x1e/0x80 |
| PGD 1e0e067 P4D 1e0e067 PUD 1e10067 PMD 235c067 PTE 0 |
| Oops: 0002 [#1] SMP PTI |
| Modules linked in: |
| CPU: 0 PID: 512 Comm: kworker/u2:0 Not tainted 4.14.33-52.13.amzn1.x86_64 #1 |
| Hardware name: Xen HVM domU, BIOS 3.4.3.amazon 11/11/2016 |
| task: ffff88002531d700 task.stack: ffffc90000480000 |
| RIP: 0010:__xen_evtchn_do_upcall+0x1e/0x80 |
| RSP: 0000:ffff880025403ef0 EFLAGS: 00010046 |
| RAX: ffffffff813cc760 RBX: ffffffffff200000 RCX: ffffc90000483ef0 |
| RDX: ffff880020540a00 RSI: ffff880023c78000 RDI: 000000000000001c |
| RBP: 0000000000000001 R08: 0000000000000000 R09: 0000000000000000 |
| R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 |
| R13: ffff880025403f5c R14: 0000000000000000 R15: 0000000000000000 |
| FS: 0000000000000000(0000) GS:ffff880025400000(0000) knlGS:0000000000000000 |
| CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 |
| CR2: ffffffffff200000 CR3: 0000000001e0a000 CR4: 00000000000006f0 |
| Call Trace: |
| <IRQ> |
| do_hvm_evtchn_intr+0xa/0x10 |
| __handle_irq_event_percpu+0x43/0x1a0 |
| handle_irq_event_percpu+0x20/0x50 |
| handle_irq_event+0x39/0x60 |
| handle_fasteoi_irq+0x80/0x140 |
| handle_irq+0xaf/0x120 |
| do_IRQ+0x41/0xd0 |
| common_interrupt+0x7d/0x7d |
| </IRQ> |
| |
| During boot, the HYPERVISOR_shared_info page gets remapped to make it work |
| with KASLR. This means that any pointer derived from it needs to be |
| adjusted. |
| |
| The only value that this applies to is the vcpu_info pointer for VCPU 0. |
| For PV and HVM with the callback vector feature, this gets done via the |
| smp_ops prepare_boot_cpu callback. Older Xen versions do not support the |
| HVM callback vector, so there is no Xen-specific smp_ops set up in that |
| scenario. So, the vcpu_info pointer for VCPU 0 never gets set to the proper |
| value, and the first reference of it will be bad. Fix this by resetting it |
| immediately after the remap. |
| |
| Signed-off-by: Frank van der Linden <fllinden@amazon.com> |
| Reviewed-by: Eduardo Valentin <eduval@amazon.com> |
| Reviewed-by: Alakesh Haloi <alakeshh@amazon.com> |
| Reviewed-by: Vallish Vaidyeshwara <vallish@amazon.com> |
| Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com> |
| Cc: Juergen Gross <jgross@suse.com> |
| Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> |
| Cc: xen-devel@lists.xenproject.org |
| Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com> |
| Signed-off-by: Sasha Levin <alexander.levin@microsoft.com> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| arch/x86/xen/enlighten_hvm.c | 13 +++++++++++++ |
| 1 file changed, 13 insertions(+) |
| |
| --- a/arch/x86/xen/enlighten_hvm.c |
| +++ b/arch/x86/xen/enlighten_hvm.c |
| @@ -65,6 +65,19 @@ static void __init xen_hvm_init_mem_mapp |
| { |
| early_memunmap(HYPERVISOR_shared_info, PAGE_SIZE); |
| HYPERVISOR_shared_info = __va(PFN_PHYS(shared_info_pfn)); |
| + |
| + /* |
| + * The virtual address of the shared_info page has changed, so |
| + * the vcpu_info pointer for VCPU 0 is now stale. |
| + * |
| + * The prepare_boot_cpu callback will re-initialize it via |
| + * xen_vcpu_setup, but we can't rely on that to be called for |
| + * old Xen versions (xen_have_vector_callback == 0). |
| + * |
| + * It is, in any case, bad to have a stale vcpu_info pointer |
| + * so reset it now. |
| + */ |
| + xen_vcpu_info_reset(0); |
| } |
| |
| static void __init init_hvm_pv_info(void) |