diff options
| author | Fangyu Yu <fangyu.yu@linux.alibaba.com> | 2025-10-16 09:26:59 +0800 |
|---|---|---|
| committer | Anup Patel <anup@brainfault.org> | 2025-10-17 13:10:01 +0530 |
| commit | 873f10cf8e4d59605bc38fa1051dea8ee56fe3be (patch) | |
| tree | b8bb4b1c9c0c996e94c5d817b690e3fc4e5451f3 | |
| parent | ea138a607709bf72c162f62d2a670fe899d73daa (diff) | |
RISC-V: KVM: Read HGEIP CSR on the correct cpu
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: 4cec89db80ba ("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>
| -rw-r--r-- | arch/riscv/kvm/aia_imsic.c | 16 |
1 files changed, 14 insertions, 2 deletions
diff --git a/arch/riscv/kvm/aia_imsic.c b/arch/riscv/kvm/aia_imsic.c index fda0346f0ea1..11422cb95a64 100644 --- a/arch/riscv/kvm/aia_imsic.c +++ b/arch/riscv/kvm/aia_imsic.c @@ -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; |