linux-kernel - Re: [PATCH] KVM: s390: pci: fix GAIT physical vs virtual pointers usage

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Date:   Fri, 9 Sep 2022 11:52:28 +0200
From:   Claudio Imbrenda <imbrenda@...ux.ibm.com>
To:     Matthew Rosato <mjrosato@...ux.ibm.com>
Cc:     linux-s390@...r.kernel.org, nrb@...ux.ibm.com,
        pmorel@...ux.ibm.com, schnelle@...ux.ibm.com, farman@...ux.ibm.com,
        borntraeger@...ux.ibm.com, hca@...ux.ibm.com, gor@...ux.ibm.com,
        agordeev@...ux.ibm.com, svens@...ux.ibm.com, frankja@...ux.ibm.com,
        david@...hat.com, kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KVM: s390: pci: fix GAIT physical vs virtual pointers
 usage

On Wed,  7 Sep 2022 11:59:52 -0400
Matthew Rosato <mjrosato@...ux.ibm.com> wrote:

> The GAIT and all of its entries must be represented by physical
> addresses as this structure is shared with underlying firmware.
> We can keep a virtual address of the GAIT origin in order to
> handle processing in the kernel, but when traversing the entries
> we must again convert the physical AISB stored in that GAIT entry
> into a virtual address in order to process it.
> 
> Note: this currently doesn't fix a real bug, since virtual addresses
> are indentical to physical ones.
> 
> Reviewed-by: Pierre Morel <pmorel@...ux.ibm.com>
> Acked-by: Nico Boehr <nrb@...ux.ibm.com>
> Signed-off-by: Matthew Rosato <mjrosato@...ux.ibm.com>

Reviewed-by: Claudio Imbrenda <imbrenda@...ux.ibm.com>

> ---
>  arch/s390/kvm/interrupt.c | 2 +-
>  arch/s390/kvm/pci.c       | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
> index b9c944b262c7..ab569faf0df2 100644
> --- a/arch/s390/kvm/interrupt.c
> +++ b/arch/s390/kvm/interrupt.c
> @@ -3324,7 +3324,7 @@ static void aen_host_forward(unsigned long si)
>  	if (gaite->count == 0)
>  		return;
>  	if (gaite->aisb != 0)
> -		set_bit_inv(gaite->aisbo, (unsigned long *)gaite->aisb);
> +		set_bit_inv(gaite->aisbo, phys_to_virt(gaite->aisb));
>  
>  	kvm = kvm_s390_pci_si_to_kvm(aift, si);
>  	if (!kvm)
> diff --git a/arch/s390/kvm/pci.c b/arch/s390/kvm/pci.c
> index bb8c335d17b9..8cfa0b03ebbb 100644
> --- a/arch/s390/kvm/pci.c
> +++ b/arch/s390/kvm/pci.c
> @@ -71,7 +71,7 @@ static int zpci_setup_aipb(u8 nisc)
>  		rc = -ENOMEM;
>  		goto free_sbv;
>  	}
> -	aift->gait = (struct zpci_gaite *)page_to_phys(page);
> +	aift->gait = (struct zpci_gaite *)page_to_virt(page);
>  
>  	zpci_aipb->aipb.faisb = virt_to_phys(aift->sbv->vector);
>  	zpci_aipb->aipb.gait = virt_to_phys(aift->gait);