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[PATCH v1 2/2] KVM: s390: Fix FOLL_*/FAULT_FLAG_* confusion

Claudio Imbrenda posted 2 patches 2 months ago
There is a newer version of this series
[PATCH v1 2/2] KVM: s390: Fix FOLL_*/FAULT_FLAG_* confusion
Posted by Claudio Imbrenda 2 months ago 
Pass the right type of flag to vcpu_dat_fault_handler(); it expects a
FOLL_* flag (in particular FOLL_WRITE), but FAULT_FLAG_WRITE is passed
instead.

This still works because they happen to have the same integer value,
but it's a mistake, thus the fix.

Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Fixes: 05066cafa925 ("s390/mm/fault: Handle guest-related program interrupts in KVM")
---
 arch/s390/kvm/kvm-s390.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index d5ad10791c25..d41d77f2c7cd 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -4954,13 +4954,13 @@ static int vcpu_dat_fault_handler(struct kvm_vcpu *vcpu, unsigned long gaddr, un
 
 static int vcpu_post_run_handle_fault(struct kvm_vcpu *vcpu)
 {
-	unsigned int flags = 0;
+	unsigned int foll = 0;
 	unsigned long gaddr;
 	int rc;
 
 	gaddr = current->thread.gmap_teid.addr * PAGE_SIZE;
 	if (kvm_s390_cur_gmap_fault_is_write())
-		flags = FAULT_FLAG_WRITE;
+		foll = FOLL_WRITE;
 
 	switch (current->thread.gmap_int_code & PGM_INT_CODE_MASK) {
 	case 0:
@@ -5002,7 +5002,7 @@ static int vcpu_post_run_handle_fault(struct kvm_vcpu *vcpu)
 			send_sig(SIGSEGV, current, 0);
 		if (rc != -ENXIO)
 			break;
-		flags = FAULT_FLAG_WRITE;
+		foll = FOLL_WRITE;
 		fallthrough;
 	case PGM_PROTECTION:
 	case PGM_SEGMENT_TRANSLATION:
@@ -5012,7 +5012,7 @@ static int vcpu_post_run_handle_fault(struct kvm_vcpu *vcpu)
 	case PGM_REGION_SECOND_TRANS:
 	case PGM_REGION_THIRD_TRANS:
 		kvm_s390_assert_primary_as(vcpu);
-		return vcpu_dat_fault_handler(vcpu, gaddr, flags);
+		return vcpu_dat_fault_handler(vcpu, gaddr, foll);
 	default:
 		KVM_BUG(1, vcpu->kvm, "Unexpected program interrupt 0x%x, TEID 0x%016lx",
 			current->thread.gmap_int_code, current->thread.gmap_teid.val);
-- 
2.50.1
Re: [PATCH v1 2/2] KVM: s390: Fix FOLL_*/FAULT_FLAG_* confusion
Posted by Christian Borntraeger 2 months ago 
Am 05.08.25 um 13:14 schrieb Claudio Imbrenda:
> Pass the right type of flag to vcpu_dat_fault_handler(); it expects a
> FOLL_* flag (in particular FOLL_WRITE), but FAULT_FLAG_WRITE is passed
> instead.
> 
> This still works because they happen to have the same integer value,
> but it's a mistake, thus the fix.
> 
> Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
> Fixes: 05066cafa925 ("s390/mm/fault: Handle guest-related program interrupts in KVM")

Acked-by: Christian Borntraeger <borntraeger@linux.ibm.com>

Shouldnt we rename the parameter to __kvm_s390_handle_dat_fault and
vcpu_dat_fault_handler from flags to foll as well in their
implementation and prototypes to keep this consistent?

> ---
>   arch/s390/kvm/kvm-s390.c | 8 ++++----
>   1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index d5ad10791c25..d41d77f2c7cd 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -4954,13 +4954,13 @@ static int vcpu_dat_fault_handler(struct kvm_vcpu *vcpu, unsigned long gaddr, un
>   
>   static int vcpu_post_run_handle_fault(struct kvm_vcpu *vcpu)
>   {
> -	unsigned int flags = 0;
> +	unsigned int foll = 0;
>   	unsigned long gaddr;
>   	int rc;
>   
>   	gaddr = current->thread.gmap_teid.addr * PAGE_SIZE;
>   	if (kvm_s390_cur_gmap_fault_is_write())
> -		flags = FAULT_FLAG_WRITE;
> +		foll = FOLL_WRITE;
>   
>   	switch (current->thread.gmap_int_code & PGM_INT_CODE_MASK) {
>   	case 0:
> @@ -5002,7 +5002,7 @@ static int vcpu_post_run_handle_fault(struct kvm_vcpu *vcpu)
>   			send_sig(SIGSEGV, current, 0);
>   		if (rc != -ENXIO)
>   			break;
> -		flags = FAULT_FLAG_WRITE;
> +		foll = FOLL_WRITE;
>   		fallthrough;
>   	case PGM_PROTECTION:
>   	case PGM_SEGMENT_TRANSLATION:
> @@ -5012,7 +5012,7 @@ static int vcpu_post_run_handle_fault(struct kvm_vcpu *vcpu)
>   	case PGM_REGION_SECOND_TRANS:
>   	case PGM_REGION_THIRD_TRANS:
>   		kvm_s390_assert_primary_as(vcpu);
> -		return vcpu_dat_fault_handler(vcpu, gaddr, flags);
> +		return vcpu_dat_fault_handler(vcpu, gaddr, foll);
>   	default:
>   		KVM_BUG(1, vcpu->kvm, "Unexpected program interrupt 0x%x, TEID 0x%016lx",
>   			current->thread.gmap_int_code, current->thread.gmap_teid.val);
Re: [PATCH v1 2/2] KVM: s390: Fix FOLL_*/FAULT_FLAG_* confusion
Posted by Claudio Imbrenda 2 months ago 
On Tue, 5 Aug 2025 13:44:04 +0200
Christian Borntraeger <borntraeger@de.ibm.com> wrote:

> Am 05.08.25 um 13:14 schrieb Claudio Imbrenda:
> > Pass the right type of flag to vcpu_dat_fault_handler(); it expects a
> > FOLL_* flag (in particular FOLL_WRITE), but FAULT_FLAG_WRITE is passed
> > instead.
> > 
> > This still works because they happen to have the same integer value,
> > but it's a mistake, thus the fix.
> > 
> > Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
> > Fixes: 05066cafa925 ("s390/mm/fault: Handle guest-related program interrupts in KVM")  
> 
> Acked-by: Christian Borntraeger <borntraeger@linux.ibm.com>
> 
> Shouldnt we rename the parameter to __kvm_s390_handle_dat_fault and
> vcpu_dat_fault_handler from flags to foll as well in their
> implementation and prototypes to keep this consistent?

that's a fair point

a patch in an upcoming series will do that, but I guess I can move that
change here instead.

I'll send a v2 later on today

> 
> > ---
> >   arch/s390/kvm/kvm-s390.c | 8 ++++----
> >   1 file changed, 4 insertions(+), 4 deletions(-)
> > 
> > diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> > index d5ad10791c25..d41d77f2c7cd 100644
> > --- a/arch/s390/kvm/kvm-s390.c
> > +++ b/arch/s390/kvm/kvm-s390.c
> > @@ -4954,13 +4954,13 @@ static int vcpu_dat_fault_handler(struct kvm_vcpu *vcpu, unsigned long gaddr, un
> >   
> >   static int vcpu_post_run_handle_fault(struct kvm_vcpu *vcpu)
> >   {
> > -	unsigned int flags = 0;
> > +	unsigned int foll = 0;
> >   	unsigned long gaddr;
> >   	int rc;
> >   
> >   	gaddr = current->thread.gmap_teid.addr * PAGE_SIZE;
> >   	if (kvm_s390_cur_gmap_fault_is_write())
> > -		flags = FAULT_FLAG_WRITE;
> > +		foll = FOLL_WRITE;
> >   
> >   	switch (current->thread.gmap_int_code & PGM_INT_CODE_MASK) {
> >   	case 0:
> > @@ -5002,7 +5002,7 @@ static int vcpu_post_run_handle_fault(struct kvm_vcpu *vcpu)
> >   			send_sig(SIGSEGV, current, 0);
> >   		if (rc != -ENXIO)
> >   			break;
> > -		flags = FAULT_FLAG_WRITE;
> > +		foll = FOLL_WRITE;
> >   		fallthrough;
> >   	case PGM_PROTECTION:
> >   	case PGM_SEGMENT_TRANSLATION:
> > @@ -5012,7 +5012,7 @@ static int vcpu_post_run_handle_fault(struct kvm_vcpu *vcpu)
> >   	case PGM_REGION_SECOND_TRANS:
> >   	case PGM_REGION_THIRD_TRANS:
> >   		kvm_s390_assert_primary_as(vcpu);
> > -		return vcpu_dat_fault_handler(vcpu, gaddr, flags);
> > +		return vcpu_dat_fault_handler(vcpu, gaddr, foll);
> >   	default:
> >   		KVM_BUG(1, vcpu->kvm, "Unexpected program interrupt 0x%x, TEID 0x%016lx",
> >   			current->thread.gmap_int_code, current->thread.gmap_teid.val);  
>
Re: [PATCH v1 2/2] KVM: s390: Fix FOLL_*/FAULT_FLAG_* confusion
Posted by David Hildenbrand 2 months ago 
On 05.08.25 13:14, Claudio Imbrenda wrote:
> Pass the right type of flag to vcpu_dat_fault_handler(); it expects a
> FOLL_* flag (in particular FOLL_WRITE), but FAULT_FLAG_WRITE is passed
> instead.
> 
> This still works because they happen to have the same integer value,
> but it's a mistake, thus the fix.
> 
> Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
> Fixes: 05066cafa925 ("s390/mm/fault: Handle guest-related program interrupts in KVM")
> ---

Reviewed-by: David Hildenbrand <david@redhat.com>

-- 
Cheers,

David / dhildenb

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