From 9d3ee578e2dbc044986d40d6b4729a7e44732e46 Mon Sep 17 00:00:00 2001 From: Julien Grall Date: Tue, 5 May 2015 16:02:09 +0100 Subject: [PATCH] xen/arm: p2m: Restrict preemption check in apply_p2m_changes The commit 569fb6c "xen/arm: Data abort exception (R/W) mem_access events" makes apply_p2m_changes to call hypercall_preempt_check for any operation rather than for relinquish. The function hypercall_preempt_check call local_events_need_delivery which rely on the current VCPU is not an idle VCPU. Although, during DOM0 building the current VCPU is an idle one. This would make Xen crash with the following stack trace: (XEN) CPU0: Unexpected Trap: Data Abort [...] (XEN) Xen call trace: (XEN) [<00256ef4>] apply_p2m_changes+0x210/0x1190 (PC) (XEN) [<002506b4>] gic_events_need_delivery+0x5c/0x13c (LR) (XEN) [<002580ec>] map_mmio_regions+0x64/0x74 (XEN) [<00251958>] gicv2v_setup+0xf8/0x150 (XEN) [<00250964>] gicv_setup+0x20/0x30 (XEN) [<0024cb3c>] arch_domain_create+0x170/0x244 (XEN) [<00207df0>] domain_create+0x2ac/0x4d8 (XEN) [<0028e3d0>] start_xen+0xcbc/0xee4 (XEN) [<00200540>] paging+0x94/0xd8 (XEN) (XEN) (XEN) **************************************** (XEN) Panic on CPU 0: (XEN) CPU0: Unexpected Trap: Data Abort (XEN) (XEN) **************************************** hypercall_preempt_check is expecting to be call only when the current VCPU belong to a real domain (see x86 behavior). As the bug prevents Xen booting on some platform, fix it by only check preemption when the current VCPU is an idle one for now. We could improve it later. Reported-by: Riku Voipio Signed-off-by: Julien Grall CC: Tamas K Lengyel Acked-by: Ian Campbell --- xen/arch/arm/p2m.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c index 65efa949e5..59dd23a7f1 100644 --- a/xen/arch/arm/p2m.c +++ b/xen/arch/arm/p2m.c @@ -948,6 +948,7 @@ static int apply_p2m_changes(struct domain *d, const unsigned long sgfn = paddr_to_pfn(start_gpaddr), egfn = paddr_to_pfn(end_gpaddr); const unsigned int preempt_count_limit = (op == MEMACCESS) ? 1 : 0x2000; + const bool_t preempt = !is_idle_vcpu(current); bool_t flush = false; bool_t flush_pt; @@ -980,7 +981,8 @@ static int apply_p2m_changes(struct domain *d, * always make at least one pass as long as preempt_count_limit is * initialized with a value >= 1. */ - if ( count >= preempt_count_limit && hypercall_preempt_check() ) + if ( preempt && count >= preempt_count_limit + && hypercall_preempt_check() ) { switch ( op ) { -- 2.30.2