The patch below does not apply to the 5.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From dfb5c1e12c28e35e4d4e5bc8022b0e9d585b89a7 Mon Sep 17 00:00:00 2001
From: Wei Liu wei.liu@kernel.org Date: Fri, 10 Sep 2021 18:57:14 +0000 Subject: [PATCH] x86/hyperv: remove on-stack cpumask from hv_send_ipi_mask_allbutself
It is not a good practice to allocate a cpumask on stack, given it may consume up to 1 kilobytes of stack space if the kernel is configured to have 8192 cpus.
The internal helper functions __send_ipi_mask{,_ex} need to loop over the provided mask anyway, so it is not too difficult to skip `self' there. We can thus do away with the on-stack cpumask in hv_send_ipi_mask_allbutself.
Adjust call sites of __send_ipi_mask as needed.
Reported-by: Linus Torvalds torvalds@linux-foundation.org Suggested-by: Michael Kelley mikelley@microsoft.com Suggested-by: Linus Torvalds torvalds@linux-foundation.org Fixes: 68bb7bfb7985d ("X86/Hyper-V: Enable IPI enlightenments") Signed-off-by: Wei Liu wei.liu@kernel.org Reviewed-by: Michael Kelley mikelley@microsoft.com Link: https://lore.kernel.org/r/20210910185714.299411-3-wei.liu@kernel.org
diff --git a/arch/x86/hyperv/hv_apic.c b/arch/x86/hyperv/hv_apic.c index 90e682a92820..32a1ad356c18 100644 --- a/arch/x86/hyperv/hv_apic.c +++ b/arch/x86/hyperv/hv_apic.c @@ -99,7 +99,8 @@ static void hv_apic_eoi_write(u32 reg, u32 val) /* * IPI implementation on Hyper-V. */ -static bool __send_ipi_mask_ex(const struct cpumask *mask, int vector) +static bool __send_ipi_mask_ex(const struct cpumask *mask, int vector, + bool exclude_self) { struct hv_send_ipi_ex **arg; struct hv_send_ipi_ex *ipi_arg; @@ -123,7 +124,10 @@ static bool __send_ipi_mask_ex(const struct cpumask *mask, int vector)
if (!cpumask_equal(mask, cpu_present_mask)) { ipi_arg->vp_set.format = HV_GENERIC_SET_SPARSE_4K; - nr_bank = cpumask_to_vpset(&(ipi_arg->vp_set), mask); + 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; @@ -138,15 +142,25 @@ static bool __send_ipi_mask_ex(const struct cpumask *mask, int vector) return hv_result_success(status); }
-static bool __send_ipi_mask(const struct cpumask *mask, int vector) +static bool __send_ipi_mask(const struct cpumask *mask, int vector, + bool exclude_self) { - int cur_cpu, vcpu; + int cur_cpu, vcpu, this_cpu = smp_processor_id(); struct hv_send_ipi ipi_arg; u64 status; + unsigned int weight;
trace_hyperv_send_ipi_mask(mask, vector);
- if (cpumask_empty(mask)) + weight = cpumask_weight(mask); + + /* + * Do nothing if + * 1. the mask is empty + * 2. the mask only contains self when exclude_self is true + */ + if (weight == 0 || + (exclude_self && weight == 1 && cpumask_test_cpu(this_cpu, mask))) return true;
if (!hv_hypercall_pg) @@ -172,6 +186,8 @@ static bool __send_ipi_mask(const struct cpumask *mask, int vector) ipi_arg.cpu_mask = 0;
for_each_cpu(cur_cpu, mask) { + if (exclude_self && cur_cpu == this_cpu) + continue; vcpu = hv_cpu_number_to_vp_number(cur_cpu); if (vcpu == VP_INVAL) return false; @@ -191,7 +207,7 @@ static bool __send_ipi_mask(const struct cpumask *mask, int vector) return hv_result_success(status);
do_ex_hypercall: - return __send_ipi_mask_ex(mask, vector); + return __send_ipi_mask_ex(mask, vector, exclude_self); }
static bool __send_ipi_one(int cpu, int vector) @@ -208,7 +224,7 @@ static bool __send_ipi_one(int cpu, int vector) return false;
if (vp >= 64) - return __send_ipi_mask_ex(cpumask_of(cpu), vector); + return __send_ipi_mask_ex(cpumask_of(cpu), vector, false);
status = hv_do_fast_hypercall16(HVCALL_SEND_IPI, vector, BIT_ULL(vp)); return hv_result_success(status); @@ -222,20 +238,13 @@ static void hv_send_ipi(int cpu, int vector)
static void hv_send_ipi_mask(const struct cpumask *mask, int vector) { - if (!__send_ipi_mask(mask, vector)) + if (!__send_ipi_mask(mask, vector, false)) orig_apic.send_IPI_mask(mask, vector); }
static void hv_send_ipi_mask_allbutself(const struct cpumask *mask, int vector) { - unsigned int this_cpu = smp_processor_id(); - struct cpumask new_mask; - const struct cpumask *local_mask; - - cpumask_copy(&new_mask, mask); - cpumask_clear_cpu(this_cpu, &new_mask); - local_mask = &new_mask; - if (!__send_ipi_mask(local_mask, vector)) + if (!__send_ipi_mask(mask, vector, true)) orig_apic.send_IPI_mask_allbutself(mask, vector); }
@@ -246,7 +255,7 @@ static void hv_send_ipi_allbutself(int vector)
static void hv_send_ipi_all(int vector) { - if (!__send_ipi_mask(cpu_online_mask, vector)) + if (!__send_ipi_mask(cpu_online_mask, vector, false)) orig_apic.send_IPI_all(vector); }