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

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Message-ID: <9b936f0c-14d0-4601-927e-89fc0b7016b6@linux.ibm.com>
Date: Wed, 14 May 2025 18:39:47 +0530
From: Ganesh G R <ganeshgr@...ux.ibm.com>
To: Narayana Murty N <nnmlinux@...ux.ibm.com>, 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: Re: [PATCH v1] powerpc/eeh: Fix missing PE bridge reconfiguration
 during VFIO EEH recovery

On 5/8/25 11:59 AM, Narayana Murty N wrote:
> 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
> 
Looks good to me.
Reviewed-by: Ganesh Goudar <ganeshgr@...ux.ibm.com>