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

[Matthew Rosato]

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@xxxxxxxxxxxxx>
> [...]
> > 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.