Re: [PATCH RFC v2 03/11] KVM: s390: Move scao validation into a function

["Christoph Schlameuss" <schlameuss@linux.ibm.com>]

On Mon Nov 10, 2025 at 10:30 PM CET, Eric Farman wrote:
> On Mon, 2025-11-10 at 18:16 +0100, Christoph Schlameuss wrote:
>> This improves readability as well as allows re-use in coming patches.
>> 
>> Signed-off-by: Christoph Schlameuss <schlameuss@linux.ibm.com>
>> ---
>>  arch/s390/kvm/vsie.c | 27 ++++++++++++++++++++-------
>>  1 file changed, 20 insertions(+), 7 deletions(-)
>> 
>> diff --git a/arch/s390/kvm/vsie.c b/arch/s390/kvm/vsie.c
>> index ced2ca4ce5b584403d900ed11cb064919feda8e9..3d602bbd1f70b7bd8ddc2c54d43027dc37a6e032 100644
>> --- a/arch/s390/kvm/vsie.c
>> +++ b/arch/s390/kvm/vsie.c
>> @@ -95,6 +95,25 @@ static int set_validity_icpt(struct kvm_s390_sie_block *scb,
>>  	return 1;
>>  }
>>  
>> +/* The sca header must not cross pages etc. */
>> +static int validate_scao(struct kvm_vcpu *vcpu, struct kvm_s390_sie_block *scb, gpa_t gpa)
>> +{
>> +	int offset;
>> +
>> +	if (gpa < 2 * PAGE_SIZE)
>> +		return set_validity_icpt(scb, 0x0038U);
>> +	if ((gpa & ~0x1fffUL) == kvm_s390_get_prefix(vcpu))
>> +		return set_validity_icpt(scb, 0x0011U);
>> +
>> +	if (sie_uses_esca(scb))
>
> This helper doesn't turn up until patch 7
>

Good catch, thank you.

I will pull up that helper into this patch then. (Decreasing the size of patch 7
is an absolute plus here.)

>> +		offset = offsetof(struct esca_block, cpu[0]) - 1;
>> +	else
>> +		offset = offsetof(struct bsca_block, cpu[0]) - 1;
>> +	if ((gpa & PAGE_MASK) != ((gpa + offset) & PAGE_MASK))
>> +		return set_validity_icpt(scb, 0x003bU);
>> +	return false;
>> +}
>> +
>>  /* mark the prefix as unmapped, this will block the VSIE */
>>  static void prefix_unmapped(struct vsie_page *vsie_page)
>>  {
>> @@ -791,13 +810,7 @@ static int pin_blocks(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
>>  
>>  	gpa = read_scao(vcpu->kvm, scb_o);
>>  	if (gpa) {
>> -		if (gpa < 2 * PAGE_SIZE)
>> -			rc = set_validity_icpt(scb_s, 0x0038U);
>> -		else if ((gpa & ~0x1fffUL) == kvm_s390_get_prefix(vcpu))
>> -			rc = set_validity_icpt(scb_s, 0x0011U);
>> -		else if ((gpa & PAGE_MASK) !=
>> -			 ((gpa + sizeof(struct bsca_block) - 1) & PAGE_MASK))
>> -			rc = set_validity_icpt(scb_s, 0x003bU);
>> +		rc = validate_scao(vcpu, scb_o, gpa);
>>  		if (!rc) {
>>  			rc = pin_guest_page(vcpu->kvm, gpa, &hpa);
>>  			if (rc)