linux-kernel - Re: [PATCH v5 11/21] KVM: s390: pci: do initial setup for AEN interpretation

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Date:   Thu, 14 Apr 2022 09:00:58 -0400
From:   Matthew Rosato <mjrosato@...ux.ibm.com>
To:     Christian Borntraeger <borntraeger@...ux.ibm.com>,
        linux-s390@...r.kernel.org
Cc:     alex.williamson@...hat.com, cohuck@...hat.com,
        schnelle@...ux.ibm.com, farman@...ux.ibm.com, pmorel@...ux.ibm.com,
        hca@...ux.ibm.com, gor@...ux.ibm.com,
        gerald.schaefer@...ux.ibm.com, agordeev@...ux.ibm.com,
        svens@...ux.ibm.com, frankja@...ux.ibm.com, david@...hat.com,
        imbrenda@...ux.ibm.com, vneethv@...ux.ibm.com,
        oberpar@...ux.ibm.com, freude@...ux.ibm.com, thuth@...hat.com,
        pasic@...ux.ibm.com, pbonzini@...hat.com, corbet@....net,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org
Subject: Re: [PATCH v5 11/21] KVM: s390: pci: do initial setup for AEN
 interpretation

On 4/14/22 3:20 AM, Christian Borntraeger wrote:
> 
> 
> Am 04.04.22 um 19:43 schrieb Matthew Rosato:
>> Initial setup for Adapter Event Notification Interpretation for zPCI
>> passthrough devices.  Specifically, allocate a structure for 
>> forwarding of
>> adapter events and pass the address of this structure to firmware.
>>
>> Signed-off-by: Matthew Rosato <mjrosato@...ux.ibm.com>
> [...]
>> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
>> index 156d1c25a3c1..9db6f8080f71 100644
>> --- a/arch/s390/kvm/kvm-s390.c
>> +++ b/arch/s390/kvm/kvm-s390.c
>> @@ -47,6 +47,7 @@
>>   #include <asm/fpu/api.h>
>>   #include "kvm-s390.h"
>>   #include "gaccess.h"
>> +#include "pci.h"
>>   #define CREATE_TRACE_POINTS
>>   #include "trace.h"
>> @@ -502,6 +503,14 @@ int kvm_arch_init(void *opaque)
>>           goto out;
>>       }
>> +    if (kvm_s390_pci_interp_allowed()) {
>> +        rc = kvm_s390_pci_init();
>> +        if (rc) {
>> +            pr_err("Unable to allocate AIFT for PCI\n");
>> +            goto out;
>> +        }
>> +    }
>> +
>>       rc = kvm_s390_gib_init(GAL_ISC);
>>       if (rc)
>>           goto out;
> 
> We would not free the aift that was allocated by kvm_s390_pci_init
> in kvm_arch_exit.
> Wouldnt we re-allocate a new aift when we unload/reload kvm forgetting 
> about the old one?

Oops, yes it looks like that's the case.  We must back-pocket a certain 
subset of firmware-shared structures (e.g. zpci_aipb and zpci_aif_sbv) 
as these cannot change for the life of the system once registered with 
firmware; but the aift is a kernel-only structure that should be safe to 
free until next module load.  I think this can be done at the end of 
kvm_s390_pci_aen_exit (with some caller adjustments re: the aift mutex)
> 
> 
>> diff --git a/arch/s390/kvm/pci.c b/arch/s390/kvm/pci.c
> [...]
>> +static int zpci_setup_aipb(u8 nisc)
> [...]
>> +    size = get_order(PAGE_ALIGN(ZPCI_NR_DEVICES *
>> +                        sizeof(struct zpci_gaite)));
> [...]
>> +    if (zpci_set_irq_ctrl(SIC_SET_AENI_CONTROLS, 0, zpci_aipb)) {
>> +        rc = -EIO;
>> +        goto free_gait;
>> +    }
>> +
>> +    return 0;
>> +
>> +free_gait:
>> +    size = get_order(PAGE_ALIGN(ZPCI_NR_DEVICES *
>> +                    sizeof(struct zpci_gaite)));
> 
> size should still be valid here?

Good point

> 
>> +    free_pages((unsigned long)aift->gait, size);
>> +free_sbv:
>> +    airq_iv_release(aift->sbv);
>> +    zpci_aif_sbv = 0;
>> +free_aipb:
>> +    kfree(zpci_aipb);
>> +    zpci_aipb = 0;
>> +
>> +    return rc;
>> +}
>> +
> 
> The remaining parts look sane.