From f5c20e4a5f18677e22d8dd2846066251b006a62d Mon Sep 17 00:00:00 2001 From: Vitaly Kuznetsov Date: Wed, 6 Oct 2021 14:50:16 +0200 Subject: [PATCH] x86/hyperv: Avoid erroneously sending IPI to 'self' __send_ipi_mask_ex() uses an optimization: when the target CPU mask is equal to 'cpu_present_mask' it uses 'HV_GENERIC_SET_ALL' format to avoid converting the specified cpumask to VP_SET. This case was overlooked when 'exclude_self' parameter was added. As the result, a spurious IPI to 'self' can be send. Reported-by: Thomas Gleixner Fixes: dfb5c1e12c28 ("x86/hyperv: remove on-stack cpumask from hv_send_ipi_mask_allbutself") Signed-off-by: Vitaly Kuznetsov Reviewed-by: Michael Kelley Link: https://lore.kernel.org/r/20211006125016.941616-1-vkuznets@redhat.com Signed-off-by: Wei Liu --- arch/x86/hyperv/hv_apic.c | 20 +++++++++++++++----- 1 file changed, 15 insertions(+), 5 deletions(-) diff --git a/arch/x86/hyperv/hv_apic.c b/arch/x86/hyperv/hv_apic.c index 32a1ad356c18..db2d92fb44da 100644 --- a/arch/x86/hyperv/hv_apic.c +++ b/arch/x86/hyperv/hv_apic.c @@ -122,17 +122,27 @@ static bool __send_ipi_mask_ex(const struct cpumask *mask, int vector, ipi_arg->reserved = 0; ipi_arg->vp_set.valid_bank_mask = 0; - if (!cpumask_equal(mask, cpu_present_mask)) { + /* + * Use HV_GENERIC_SET_ALL and avoid converting cpumask to VP_SET + * when the IPI is sent to all currently present CPUs. + */ + if (!cpumask_equal(mask, cpu_present_mask) || exclude_self) { ipi_arg->vp_set.format = HV_GENERIC_SET_SPARSE_4K; if (exclude_self) nr_bank = cpumask_to_vpset_noself(&(ipi_arg->vp_set), mask); else nr_bank = cpumask_to_vpset(&(ipi_arg->vp_set), mask); - } - if (nr_bank < 0) - goto ipi_mask_ex_done; - if (!nr_bank) + + /* + * 'nr_bank <= 0' means some CPUs in cpumask can't be + * represented in VP_SET. Return an error and fall back to + * native (architectural) method of sending IPIs. + */ + if (nr_bank <= 0) + goto ipi_mask_ex_done; + } else { ipi_arg->vp_set.format = HV_GENERIC_SET_ALL; + } status = hv_do_rep_hypercall(HVCALL_SEND_IPI_EX, 0, nr_bank, ipi_arg, NULL); -- 2.34.1