Commit ccdb36cb authored by Amit Machhiwal's avatar Amit Machhiwal Committed by Madhavan Srinivasan
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KVM: PPC: Book3S HV: Fix IRQ map warnings with XICS on pSeries KVM Guest 



The commit 9576730d ("KVM: PPC: select IRQ_BYPASS_MANAGER") enabled
IRQ_BYPASS_MANAGER when CONFIG_KVM was set. Subsequently, commit
c57875f5 ("KVM: PPC: Book3S HV: Enable IRQ bypass") enabled IRQ
bypass and added the necessary callbacks to create/remove the mappings
between host real IRQ and the guest GSI.

The availability of IRQ bypass is determined by the arch-specific
function kvm_arch_has_irq_bypass(), which invokes
kvmppc_irq_bypass_add_producer_hv(). This function, in turn, calls
kvmppc_set_passthru_irq_hv() to create a mapping in the passthrough IRQ
map, associating a host IRQ to a guest GSI.

However, when a pSeries KVM guest (L2) is booted within an LPAR (L1)
with the kernel boot parameter `xive=off`, it defaults to using emulated
XICS controller. As an attempt to establish host IRQ to guest GSI
mappings via kvmppc_set_passthru_irq() on a PCI device hotplug
(passhthrough) operation fail, returning -ENOENT. This failure occurs
because only interrupts with EOI operations handled through OPAL calls
(verified via is_pnv_opal_msi()) are currently supported.

These mapping failures lead to below repeated warnings in the L1 host:

 [  509.220349] kvmppc_set_passthru_irq_hv: Could not assign IRQ map for (58,4970)
 [  509.220368] kvmppc_set_passthru_irq (irq 58, gsi 4970) fails: -2
 [  509.220376] vfio-pci 0015:01:00.0: irq bypass producer (token 0000000090bc635b) registration fails: -2
 ...
 [  509.291781] vfio-pci 0015:01:00.0: irq bypass producer (token 000000003822eed8) registration fails: -2

Fix this by restricting IRQ bypass enablement on pSeries systems by
making the IRQ bypass callbacks unavailable when running on pSeries
platform.

Signed-off-by: default avatarAmit Machhiwal <amachhiw@linux.ibm.com>
Tested-by: default avatarGautam Menghani <gautam@linux.ibm.com>
Reviewed-by: default avatarVaibhav Jain <vaibhav@linux.ibm.com>
Signed-off-by: default avatarMadhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/20250425185641.1611857-1-amachhiw@linux.ibm.com
parent f9cb1476

arch/powerpc/kvm/book3s_hv.c

+16 −4
Original line number Diff line number Diff line
@@ -6541,10 +6541,6 @@ static struct kvmppc_ops kvm_ops_hv = { 
	.fast_vcpu_kick = kvmppc_fast_vcpu_kick_hv,

	.arch_vm_ioctl  = kvm_arch_vm_ioctl_hv,

	.hcall_implemented = kvmppc_hcall_impl_hv,

#ifdef CONFIG_KVM_XICS

	.irq_bypass_add_producer = kvmppc_irq_bypass_add_producer_hv,

	.irq_bypass_del_producer = kvmppc_irq_bypass_del_producer_hv,

#endif

	.configure_mmu = kvmhv_configure_mmu,

	.get_rmmu_info = kvmhv_get_rmmu_info,

	.set_smt_mode = kvmhv_set_smt_mode,
@@ -6662,6 +6658,22 @@ static int kvmppc_book3s_init_hv(void) 
		return r;

	}



#if defined(CONFIG_KVM_XICS)

	/*

	 * IRQ bypass is supported only for interrupts whose EOI operations are

	 * handled via OPAL calls. Therefore, register IRQ bypass handlers

	 * exclusively for PowerNV KVM when booted with 'xive=off', indicating

	 * the use of the emulated XICS interrupt controller.

	 */

	if (!kvmhv_on_pseries()) {

		pr_info("KVM-HV: Enabling IRQ bypass\n");

		kvm_ops_hv.irq_bypass_add_producer =

			kvmppc_irq_bypass_add_producer_hv;

		kvm_ops_hv.irq_bypass_del_producer =

			kvmppc_irq_bypass_del_producer_hv;

	}

#endif



	kvm_ops_hv.owner = THIS_MODULE;

	kvmppc_hv_ops = &kvm_ops_hv;