Hi Greg,

On Mon, Sep 20, 2021 at 10:56:55AM +0200, gregkh@linuxfoundation.org wrote:

The patch below does not apply to the 5.14-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.

There is one prerequisite patch for this patch. I can backport both to all relevant stable branches, but I would like to know how you would like to receive backport patches. Several git bundles to stable@? Several two-patch series to stable@? I can also give you several tags / branches to pull from if you like.

Thanks, Wei.

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);

}