linux-kernel - [PATCH v1] powerpc/eeh: Fix missing PE bridge reconfiguration during VFIO EEH recovery

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Message-ID: <20250508062928.146043-1-nnmlinux@linux.ibm.com>
Date: Thu,  8 May 2025 02:29:28 -0400
From: Narayana Murty N <nnmlinux@...ux.ibm.com>
To: mahesh@...ux.ibm.com, maddy@...ux.ibm.com, mpe@...erman.id.au,
        linuxppc-dev@...ts.ozlabs.org
Cc: linux-kernel@...r.kernel.org, oohall@...il.com, npiggin@...il.com,
        christophe.leroy@...roup.eu, naveen@...nel.org,
        gwshan@...ux.vnet.ibm.com, benh@...nel.crashing.org, agraf@...e.de,
        vaibhav@...ux.ibm.com
Subject: [PATCH v1] powerpc/eeh: Fix missing PE bridge reconfiguration during VFIO EEH recovery

VFIO EEH recovery for PCI passthrough devices fails on PowerNV and pseries
platforms due to missing host-side PE bridge reconfiguration. In the
current implementation, eeh_pe_configure() only performs RTAS or OPAL-based
bridge reconfiguration for native host devices, but skips it entirely for
PEs managed through VFIO in guest passthrough scenarios.

This leads to incomplete EEH recovery when a PCI error affects a
passthrough device assigned to a QEMU/KVM guest. Although VFIO triggers the
EEH recovery flow through VFIO_EEH_PE_ENABLE ioctl, the platform-specific
bridge reconfiguration step is silently bypassed. As a result, the PE's
config space is not fully restored, causing subsequent config space access
failures or EEH freeze-on-access errors inside the guest.

This patch fixes the issue by ensuring that eeh_pe_configure() always
invokes the platform's configure_bridge() callback (e.g.,
pseries_eeh_phb_configure_bridge) even for VFIO-managed PEs. This ensures
that RTAS or OPAL calls to reconfigure the PE bridge are correctly issued
on the host side, restoring the PE's configuration space after an EEH
event.

This fix is essential for reliable EEH recovery in QEMU/KVM guests using
VFIO PCI passthrough on PowerNV and pseries systems.

Tested with:
- QEMU/KVM guest using VFIO passthrough (IBM Power9,(lpar)Power11 host)
- Injected EEH errors with pseries EEH errinjct tool on host, recovery
  verified on qemu guest.
- Verified successful config space access and CAP_EXP DevCtl restoration
  after recovery

Fixes: 212d16cdca2d ("powerpc/eeh: EEH support for VFIO PCI device")
Signed-off-by: Narayana Murty N <nnmlinux@...ux.ibm.com>
Reviewed-by: Vaibhav Jain <vaibhav@...ux.ibm.com>
---
 arch/powerpc/kernel/eeh.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/powerpc/kernel/eeh.c b/arch/powerpc/kernel/eeh.c
index 83fe99861eb1..ca7f7bb2b478 100644
--- a/arch/powerpc/kernel/eeh.c
+++ b/arch/powerpc/kernel/eeh.c
@@ -1509,6 +1509,8 @@ int eeh_pe_configure(struct eeh_pe *pe)
 	/* Invalid PE ? */
 	if (!pe)
 		return -ENODEV;
+	else
+		ret = eeh_ops->configure_bridge(pe);

 	return ret;
 }
--
2.48.1