From 26a799952737de20626e8c5c51b24534f1c90536 Mon Sep 17 00:00:00 2001 From: Konrad Rzeszutek Wilk Date: Fri, 16 Aug 2013 14:39:56 -0400 Subject: [PATCH] xen/smp: Update pv_lock_ops functions before alternative code starts under PVHVM Before this patch we would patch all of the pv_lock_ops sites using alternative assembler. Then later in the bootup cycle change the unlock_kick and lock_spinning to the Xen specific - without re patching. That meant that for the core of the kernel we would be running with the baremetal version of unlock_kick and lock_spinning while for modules we would have the proper Xen specific slowpaths. As most of the module uses some API from the core kernel that ended up with slowpath lockers waiting forever to be kicked (b/c they would be using the Xen specific slowpath logic). And the kick never came b/c the unlock path that was taken was the baremetal one. On PV we do not have the problem as we initialise before the alternative code kicks in. The fix is to make the updating of the pv_lock_ops function be done before the alternative code starts patching. Note that this patch fixes issues discovered by commit f10cd522c5fbfec9ae3cc01967868c9c2401ed23. ("xen: disable PV spinlocks on HVM") wherein it mentioned PV spinlocks cannot possibly work with the current code because they are enabled after pvops patching has already been done, and because PV spinlocks use a different data structure than native spinlocks so we cannot switch between them dynamically. The first problem is solved by this patch. The second problem has been solved by commit 816434ec4a674fcdb3c2221a6dffdc8f34020550 (Merge branch 'x86-spinlocks-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip) P.S. There is still the commit 70dd4998cb85f0ecd6ac892cc7232abefa432efb (xen/spinlock: Disable IRQ spinlock (PV) allocation on PVHVM) to revert but that can be done later after all other bugs have been fixed. Signed-off-by: Konrad Rzeszutek Wilk Reviewed-by: David Vrabel --- arch/x86/xen/smp.c | 19 ++++++++++++++----- 1 file changed, 14 insertions(+), 5 deletions(-) diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c index c21b825ed056..d1e4777b4e75 100644 --- a/arch/x86/xen/smp.c +++ b/arch/x86/xen/smp.c @@ -273,12 +273,20 @@ static void __init xen_smp_prepare_boot_cpu(void) BUG_ON(smp_processor_id() != 0); native_smp_prepare_boot_cpu(); - /* We've switched to the "real" per-cpu gdt, so make sure the - old memory can be recycled */ - make_lowmem_page_readwrite(xen_initial_gdt); + if (xen_pv_domain()) { + /* We've switched to the "real" per-cpu gdt, so make sure the + old memory can be recycled */ + make_lowmem_page_readwrite(xen_initial_gdt); - xen_filter_cpu_maps(); - xen_setup_vcpu_info_placement(); + xen_filter_cpu_maps(); + xen_setup_vcpu_info_placement(); + } + /* + * The alternative logic (which patches the unlock/lock) runs before + * the smp bootup up code is activated. Hence we need to set this up + * the core kernel is being patched. Otherwise we will have only + * modules patched but not core code. + */ xen_init_spinlocks(); } @@ -737,4 +745,5 @@ void __init xen_hvm_smp_init(void) smp_ops.cpu_die = xen_hvm_cpu_die; smp_ops.send_call_func_ipi = xen_smp_send_call_function_ipi; smp_ops.send_call_func_single_ipi = xen_smp_send_call_function_single_ipi; + smp_ops.smp_prepare_boot_cpu = xen_smp_prepare_boot_cpu; } -- 2.34.1