From de75abbe0121a6c3c9c6b04c75300088e57ad1d5 Mon Sep 17 00:00:00 2001 From: Vitaly Kuznetsov Date: Thu, 8 Sep 2016 11:48:28 +0200 Subject: [PATCH] arm/xen: fix SMP guests boot Commit 88e957d6e47f ("xen: introduce xen_vcpu_id mapping") broke SMP ARM guests on Xen. When FIFO-based event channels are in use (this is the default), evtchn_fifo_alloc_control_block() is called on CPU_UP_PREPARE event and this happens before we set up xen_vcpu_id mapping in xen_starting_cpu. Temporary fix the issue by setting direct Linux CPU id <-> Xen vCPU id mapping for all possible CPUs at boot. We don't currently support kexec/kdump on Xen/ARM so these ids always match. In future, we have several ways to solve the issue, e.g.: - Eliminate all hypercalls from CPU_UP_PREPARE, do them from the starting CPU. This can probably be done for both x86 and ARM and, if done, will allow us to get Xen's idea of vCPU id from CPUID/MPIDR on the starting CPU directly, no messing with ACPI/device tree required. - Save vCPU id information from ACPI/device tree on ARM and use it to initialize xen_vcpu_id mapping. This is the same trick we currently do on x86. Reported-by: Julien Grall Tested-by: Wei Chen Signed-off-by: Vitaly Kuznetsov Acked-by: Stefano Stabellini Signed-off-by: David Vrabel --- arch/arm/xen/enlighten.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c index 3d2cef6488ea..f193414d0f6f 100644 --- a/arch/arm/xen/enlighten.c +++ b/arch/arm/xen/enlighten.c @@ -170,9 +170,6 @@ static int xen_starting_cpu(unsigned int cpu) pr_info("Xen: initializing cpu%d\n", cpu); vcpup = per_cpu_ptr(xen_vcpu_info, cpu); - /* Direct vCPU id mapping for ARM guests. */ - per_cpu(xen_vcpu_id, cpu) = cpu; - info.mfn = virt_to_gfn(vcpup); info.offset = xen_offset_in_page(vcpup); @@ -330,6 +327,7 @@ static int __init xen_guest_init(void) { struct xen_add_to_physmap xatp; struct shared_info *shared_info_page = NULL; + int cpu; if (!xen_domain()) return 0; @@ -380,7 +378,8 @@ static int __init xen_guest_init(void) return -ENOMEM; /* Direct vCPU id mapping for ARM guests. */ - per_cpu(xen_vcpu_id, 0) = 0; + for_each_possible_cpu(cpu) + per_cpu(xen_vcpu_id, cpu) = cpu; xen_auto_xlat_grant_frames.count = gnttab_max_grant_frames(); if (xen_xlate_map_ballooned_pages(&xen_auto_xlat_grant_frames.pfn, -- 2.20.1