From 4313feae90068fb8fccafe401dd7976cbe117db8 Mon Sep 17 00:00:00 2001 From: Oleksii Kurochko Date: Fri, 6 Mar 2026 17:33:24 +0100 Subject: [PATCH] xen/riscv: add vtimer context switch helpers Introduce vtimer_ctxt_switch_from() and vtimer_ctxt_switch_to() to handle virtual timer state across vCPU context switches. At present, vtimer_ctxt_switch_from() is a no-op because the RISC-V SSTC extension, which provides a virtualization-aware timer, is not yet supported. Xen therefore relies the virtual (SBI-based) timer. The virtual timer uses Xen's internal timer infrastructure and must be associated with the pCPU on which the vCPU is currently running so that timer events can be delivered efficiently. As a result, vtimer_ctxt_switch_to() migrates the timer to the target pCPU when a vCPU is scheduled in. Signed-off-by: Oleksii Kurochko Acked-by: Jan Beulich --- xen/arch/riscv/include/asm/vtimer.h | 3 +++ xen/arch/riscv/vtimer.c | 15 +++++++++++++++ 2 files changed, 18 insertions(+) diff --git a/xen/arch/riscv/include/asm/vtimer.h b/xen/arch/riscv/include/asm/vtimer.h index 111863610a..b4d48d1a17 100644 --- a/xen/arch/riscv/include/asm/vtimer.h +++ b/xen/arch/riscv/include/asm/vtimer.h @@ -14,4 +14,7 @@ void vcpu_timer_destroy(struct vcpu *v); void vtimer_set_timer(struct vtimer *t, uint64_t ticks); +void vtimer_ctxt_switch_from(struct vcpu *p); +void vtimer_ctxt_switch_to(struct vcpu *n); + #endif /* ASM__RISCV__VTIMER_H */ diff --git a/xen/arch/riscv/vtimer.c b/xen/arch/riscv/vtimer.c index 32d142bcdf..afd8a53a73 100644 --- a/xen/arch/riscv/vtimer.c +++ b/xen/arch/riscv/vtimer.c @@ -1,5 +1,6 @@ /* SPDX-License-Identifier: GPL-2.0-only */ +#include #include #include @@ -69,3 +70,17 @@ void vtimer_set_timer(struct vtimer *t, const uint64_t ticks) migrate_timer(&t->timer, smp_processor_id()); set_timer(&t->timer, expires); } + +void vtimer_ctxt_switch_from(struct vcpu *p) +{ + ASSERT(!is_idle_vcpu(p)); + + /* Nothing to do at the moment as SSTC isn't supported now. */ +} + +void vtimer_ctxt_switch_to(struct vcpu *n) +{ + ASSERT(!is_idle_vcpu(n)); + + migrate_timer(&n->arch.vtimer.timer, n->processor); +}