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riscv: vector: allow non-preemptible kernel-mode vector with IRQs off

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Similar to commit 7137a203b2 ("arm64/fpsimd: Permit kernel mode NEON
with IRQs off"), we are upgrading get/put_cpu_vector_context such that
kvm_arch_vcpu_load/put can be safely called under both irq off and
regular process context.

Also, export both symbols so the kvm module can call into it.

Signed-off-by: Andy Chiu <tchiu@tenstorrent.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Link: https://lore.kernel.org/r/20260803215250.824417-3-tchiu@tenstorrent.com
Signed-off-by: Anup Patel <anup@brainfault.org>
This commit is contained in:
Andy Chiu 2026-08-03 16:52:41 -05:00 committed by Anup Patel
parent 8f798d6d7f
commit 848a973c5f
2 changed files with 16 additions and 19 deletions
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16
arch/riscv/include/asm/simd.h
View File

@ -36,20 +36,10 @@ static __must_check inline bool may_use_simd(void)
/*
* Nesting is achieved in preempt_v by spreading the control for
* preemptible and non-preemptible kernel-mode Vector into two fields.
* Always try to match with preempt_v if kernel V-context exists. Then,
* fallback to check non preempt_v if nesting happens, or if the config
* is not set.
* Only non-preempt_v can nest on top of preempt_v, if non-preempt_v is
* unavailable, then preempt_v is not allowed.
*/
if (IS_ENABLED(CONFIG_RISCV_ISA_V_PREEMPTIVE) && current->thread.kernel_vstate.datap) {
if (!riscv_preempt_v_started(current))
return true;
}
/*
* Non-preemptible kernel-mode Vector temporarily disables bh. So we
* must not return true on irq_disabled(). Otherwise we would fail the
* lockdep check calling local_bh_enable()
*/
return !irqs_disabled() && !(riscv_v_flags() & RISCV_KERNEL_MODE_V);
return !(riscv_v_flags() & RISCV_KERNEL_MODE_V);
}
#else /* ! CONFIG_RISCV_ISA_V */

19
arch/riscv/kernel/kernel_mode_vector.c
View File

@ -10,6 +10,7 @@
#include <linux/percpu.h>
#include <linux/preempt.h>
#include <linux/types.h>
#include <linux/kvm_types.h>
#include <asm/vector.h>
#include <asm/switch_to.h>
@ -55,13 +56,16 @@ void get_cpu_vector_context(void)
* disable softirqs so it is impossible for softirqs to nest
* get_cpu_vector_context() when kernel is actively using Vector.
*/
if (!IS_ENABLED(CONFIG_PREEMPT_RT))
local_bh_disable();
else
if (!IS_ENABLED(CONFIG_PREEMPT_RT)) {
if (!irqs_disabled())
local_bh_disable();
} else {
preempt_disable();
}
riscv_v_start(RISCV_KERNEL_MODE_V);
}
EXPORT_SYMBOL_FOR_KVM(get_cpu_vector_context);
/*
* Release the CPU vector context.
@ -74,11 +78,14 @@ void put_cpu_vector_context(void)
{
riscv_v_stop(RISCV_KERNEL_MODE_V);
if (!IS_ENABLED(CONFIG_PREEMPT_RT))
local_bh_enable();
else
if (!IS_ENABLED(CONFIG_PREEMPT_RT)) {
if (!irqs_disabled())
local_bh_enable();
} else {
preempt_enable();
}
}
EXPORT_SYMBOL_FOR_KVM(put_cpu_vector_context);
#ifdef CONFIG_RISCV_ISA_V_PREEMPTIVE
static __always_inline u32 *riscv_v_flags_ptr(void)