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RISC-V: KVM: Read HGEIP CSR on the correct cpu

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When executing kvm_riscv_vcpu_aia_has_interrupts, the vCPU may have
migrated and the IMSIC VS-file have not been updated yet, currently
the HGEIP CSR should be read from the imsic->vsfile_cpu ( the pCPU
before migration ) via on_each_cpu_mask, but this will trigger an
IPI call and repeated IPI within a period of time is expensive in
a many-core systems.

Just let the vCPU execute and update the correct IMSIC VS-file via
kvm_riscv_vcpu_aia_imsic_update may be a simple solution.

Fixes: 4cec89db80 ("RISC-V: KVM: Move HGEI[E|P] CSR access to IMSIC virtualization")
Signed-off-by: Fangyu Yu <fangyu.yu@linux.alibaba.com>
Reviewed-by: Guo Ren <guoren@kernel.org>
Reviewed-by: Anup Patel <anup@brainfault.org>
Tested-by: Anup Patel <anup@brainfault.org>
Link: https://lore.kernel.org/r/20251016012659.82998-1-fangyu.yu@linux.alibaba.com
Signed-off-by: Anup Patel <anup@brainfault.org>
This commit is contained in:
Fangyu Yu 2025-10-16 09:26:59 +08:00 committed by Anup Patel
parent ea138a6077
commit 873f10cf8e
1 changed files with 14 additions and 2 deletions
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16
arch/riscv/kvm/aia_imsic.c
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@ -689,8 +689,20 @@ bool kvm_riscv_vcpu_aia_imsic_has_interrupt(struct kvm_vcpu *vcpu)
*/
read_lock_irqsave(&imsic->vsfile_lock, flags);
if (imsic->vsfile_cpu > -1)
ret = !!(csr_read(CSR_HGEIP) & BIT(imsic->vsfile_hgei));
if (imsic->vsfile_cpu > -1) {
/*
* This function is typically called from kvm_vcpu_block() via
* kvm_arch_vcpu_runnable() upon WFI trap. The kvm_vcpu_block()
* can be preempted and the blocking VCPU might resume on a
* different CPU. This means it is possible that current CPU
* does not match the imsic->vsfile_cpu hence this function
* must check imsic->vsfile_cpu before accessing HGEIP CSR.
*/
if (imsic->vsfile_cpu != vcpu->cpu)
ret = true;
else
ret = !!(csr_read(CSR_HGEIP) & BIT(imsic->vsfile_hgei));
}
read_unlock_irqrestore(&imsic->vsfile_lock, flags);
return ret;