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

[fangyu.yu at linux.alibaba.com]

From: Fangyu Yu <fangyu.yu at linux.alibaba.com>

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 at linux.alibaba.com>
---
 arch/riscv/kvm/aia_imsic.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/arch/riscv/kvm/aia_imsic.c b/arch/riscv/kvm/aia_imsic.c
index fda0346f0ea1..168c02ad0a78 100644
--- a/arch/riscv/kvm/aia_imsic.c
+++ b/arch/riscv/kvm/aia_imsic.c
@@ -689,8 +689,12 @@ 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) {
+		if (imsic->vsfile_cpu != smp_processor_id())
+			ret = true;
+		else
+			ret = !!(csr_read(CSR_HGEIP) & BIT(imsic->vsfile_hgei));
+	}
 	read_unlock_irqrestore(&imsic->vsfile_lock, flags);
 
 	return ret;
-- 
2.50.1