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Date: Fri, 10 Sep 2021 18:57:14 +0000
From: Wei Liu <wei.liu@...nel.org>
To: Linux on Hyper-V List <linux-hyperv@...r.kernel.org>
Cc: Michael Kelley <mikelley@...rosoft.com>, kys@...rosoft.com,
haiyangz@...rosoft.com, decui@...rosoft.com,
sthemmin@...rosoft.com, Wei Liu <wei.liu@...nel.org>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
x86@...nel.org (maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)),
"H. Peter Anvin" <hpa@...or.com>,
linux-kernel@...r.kernel.org (open list:X86 ARCHITECTURE (32-BIT AND
64-BIT))
Subject: [PATCH v2 2/2] 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@...ux-foundation.org>
Suggested-by: Michael Kelley <mikelley@...rosoft.com>
Suggested-by: Linus Torvalds <torvalds@...ux-foundation.org>
Fixes: 68bb7bfb7985d ("X86/Hyper-V: Enable IPI enlightenments")
Signed-off-by: Wei Liu <wei.liu@...nel.org>
---
v2: more robust check in __send_ipi_mask
---
arch/x86/hyperv/hv_apic.c | 43 +++++++++++++++++++++++----------------
1 file changed, 26 insertions(+), 17 deletions(-)
diff --git a/arch/x86/hyperv/hv_apic.c b/arch/x86/hyperv/hv_apic.c
index 90e682a92820..48aefcea724b 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_first(mask) == this_cpu))
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);
}
--
2.30.2
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