KVM: s390: fix memory slot handling for KVM_SET_USER_MEMORY_REGION
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Message ID 20190524140623.104033-1-borntraeger@de.ibm.com
State New
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Series
  • KVM: s390: fix memory slot handling for KVM_SET_USER_MEMORY_REGION
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Commit Message

Christian Borntraeger May 24, 2019, 2:06 p.m. UTC
kselftests exposed a problem in the s390 handling for memory slots.
Right now we only do proper memory slot handling for creation of new
memory slots. Neither MOVE, nor DELETION are handled properly. Let us
implement those.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
---
 arch/s390/kvm/kvm-s390.c | 35 +++++++++++++++++++++--------------
 1 file changed, 21 insertions(+), 14 deletions(-)

Comments

Paolo Bonzini May 24, 2019, 7:21 p.m. UTC | #1
On 24/05/19 16:06, Christian Borntraeger wrote:
> kselftests exposed a problem in the s390 handling for memory slots.
> Right now we only do proper memory slot handling for creation of new
> memory slots. Neither MOVE, nor DELETION are handled properly. Let us
> implement those.
> 
> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
> ---
>  arch/s390/kvm/kvm-s390.c | 35 +++++++++++++++++++++--------------
>  1 file changed, 21 insertions(+), 14 deletions(-)
> 
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index 871d2e99b156..6ec0685ab2c7 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -4525,21 +4525,28 @@ void kvm_arch_commit_memory_region(struct kvm *kvm,
>  				const struct kvm_memory_slot *new,
>  				enum kvm_mr_change change)
>  {
> -	int rc;
> +	int rc = 0;
>  
> -	/* If the basics of the memslot do not change, we do not want
> -	 * to update the gmap. Every update causes several unnecessary
> -	 * segment translation exceptions. This is usually handled just
> -	 * fine by the normal fault handler + gmap, but it will also
> -	 * cause faults on the prefix page of running guest CPUs.
> -	 */
> -	if (old->userspace_addr == mem->userspace_addr &&
> -	    old->base_gfn * PAGE_SIZE == mem->guest_phys_addr &&
> -	    old->npages * PAGE_SIZE == mem->memory_size)
> -		return;
> -
> -	rc = gmap_map_segment(kvm->arch.gmap, mem->userspace_addr,
> -		mem->guest_phys_addr, mem->memory_size);
> +	switch (change) {
> +	case KVM_MR_DELETE:
> +		rc = gmap_unmap_segment(kvm->arch.gmap, old->base_gfn * PAGE_SIZE,
> +					old->npages * PAGE_SIZE);
> +		break;
> +	case KVM_MR_MOVE:
> +		rc = gmap_unmap_segment(kvm->arch.gmap, old->base_gfn * PAGE_SIZE,
> +					old->npages * PAGE_SIZE);
> +		if (rc)
> +			break;
> +		/* FALLTHROUGH */
> +	case KVM_MR_CREATE:
> +		rc = gmap_map_segment(kvm->arch.gmap, mem->userspace_addr,
> +				      mem->guest_phys_addr, mem->memory_size);
> +		break;
> +	case KVM_MR_FLAGS_ONLY:
> +		break;
> +	default:
> +		WARN(1, "Unknown KVM MR CHANGE: %d\n", change);
> +	}
>  	if (rc)
>  		pr_warn("failed to commit memory region\n");
>  	return;
> 

Queued for 5.2-rc2, thanks.

Paolo
Thomas Huth May 27, 2019, 7:39 a.m. UTC | #2
On 24/05/2019 16.06, Christian Borntraeger wrote:
> kselftests exposed a problem in the s390 handling for memory slots.
> Right now we only do proper memory slot handling for creation of new
> memory slots. Neither MOVE, nor DELETION are handled properly. Let us
> implement those.
> 
> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
> ---
>  arch/s390/kvm/kvm-s390.c | 35 +++++++++++++++++++++--------------
>  1 file changed, 21 insertions(+), 14 deletions(-)
> 
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index 871d2e99b156..6ec0685ab2c7 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -4525,21 +4525,28 @@ void kvm_arch_commit_memory_region(struct kvm *kvm,
>  				const struct kvm_memory_slot *new,
>  				enum kvm_mr_change change)
>  {
> -	int rc;
> +	int rc = 0;
>  
> -	/* If the basics of the memslot do not change, we do not want
> -	 * to update the gmap. Every update causes several unnecessary
> -	 * segment translation exceptions. This is usually handled just
> -	 * fine by the normal fault handler + gmap, but it will also
> -	 * cause faults on the prefix page of running guest CPUs.
> -	 */
> -	if (old->userspace_addr == mem->userspace_addr &&
> -	    old->base_gfn * PAGE_SIZE == mem->guest_phys_addr &&
> -	    old->npages * PAGE_SIZE == mem->memory_size)
> -		return;

This check is now gone in the new code. Maybe mention the reason in the
patch description?

> -	rc = gmap_map_segment(kvm->arch.gmap, mem->userspace_addr,
> -		mem->guest_phys_addr, mem->memory_size);
> +	switch (change) {
> +	case KVM_MR_DELETE:
> +		rc = gmap_unmap_segment(kvm->arch.gmap, old->base_gfn * PAGE_SIZE,
> +					old->npages * PAGE_SIZE);
> +		break;
> +	case KVM_MR_MOVE:
> +		rc = gmap_unmap_segment(kvm->arch.gmap, old->base_gfn * PAGE_SIZE,
> +					old->npages * PAGE_SIZE);
> +		if (rc)
> +			break;
> +		/* FALLTHROUGH */
> +	case KVM_MR_CREATE:
> +		rc = gmap_map_segment(kvm->arch.gmap, mem->userspace_addr,
> +				      mem->guest_phys_addr, mem->memory_size);
> +		break;
> +	case KVM_MR_FLAGS_ONLY:
> +		break;
> +	default:
> +		WARN(1, "Unknown KVM MR CHANGE: %d\n", change);
> +	}
>  	if (rc)
>  		pr_warn("failed to commit memory region\n");
>  	return;
> 

Looks good to me, but I'm not an expert in this area, so FWIW a weak:

Reviewed-by: Thomas Huth <thuth@redhat.com>
Christian Borntraeger May 27, 2019, 8:04 a.m. UTC | #3
On 27.05.19 09:39, Thomas Huth wrote:
> On 24/05/2019 16.06, Christian Borntraeger wrote:
>> kselftests exposed a problem in the s390 handling for memory slots.
>> Right now we only do proper memory slot handling for creation of new
>> memory slots. Neither MOVE, nor DELETION are handled properly. Let us
>> implement those.
>>
>> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
>> ---
>>  arch/s390/kvm/kvm-s390.c | 35 +++++++++++++++++++++--------------
>>  1 file changed, 21 insertions(+), 14 deletions(-)
>>
>> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
>> index 871d2e99b156..6ec0685ab2c7 100644
>> --- a/arch/s390/kvm/kvm-s390.c
>> +++ b/arch/s390/kvm/kvm-s390.c
>> @@ -4525,21 +4525,28 @@ void kvm_arch_commit_memory_region(struct kvm *kvm,
>>  				const struct kvm_memory_slot *new,
>>  				enum kvm_mr_change change)
>>  {
>> -	int rc;
>> +	int rc = 0;
>>  
>> -	/* If the basics of the memslot do not change, we do not want
>> -	 * to update the gmap. Every update causes several unnecessary
>> -	 * segment translation exceptions. This is usually handled just
>> -	 * fine by the normal fault handler + gmap, but it will also
>> -	 * cause faults on the prefix page of running guest CPUs.
>> -	 */
>> -	if (old->userspace_addr == mem->userspace_addr &&
>> -	    old->base_gfn * PAGE_SIZE == mem->guest_phys_addr &&
>> -	    old->npages * PAGE_SIZE == mem->memory_size)
>> -		return;
> 
> This check is now gone in the new code. Maybe mention the reason in the
> patch description?

Yes, all these checks are done in common code (and they result in the KVM_MR types).

> 
>> -	rc = gmap_map_segment(kvm->arch.gmap, mem->userspace_addr,
>> -		mem->guest_phys_addr, mem->memory_size);
>> +	switch (change) {
>> +	case KVM_MR_DELETE:
>> +		rc = gmap_unmap_segment(kvm->arch.gmap, old->base_gfn * PAGE_SIZE,
>> +					old->npages * PAGE_SIZE);
>> +		break;
>> +	case KVM_MR_MOVE:
>> +		rc = gmap_unmap_segment(kvm->arch.gmap, old->base_gfn * PAGE_SIZE,
>> +					old->npages * PAGE_SIZE);
>> +		if (rc)
>> +			break;
>> +		/* FALLTHROUGH */
>> +	case KVM_MR_CREATE:
>> +		rc = gmap_map_segment(kvm->arch.gmap, mem->userspace_addr,
>> +				      mem->guest_phys_addr, mem->memory_size);
>> +		break;
>> +	case KVM_MR_FLAGS_ONLY:
>> +		break;
>> +	default:
>> +		WARN(1, "Unknown KVM MR CHANGE: %d\n", change);
>> +	}
>>  	if (rc)
>>  		pr_warn("failed to commit memory region\n");
>>  	return;
>>
> 
> Looks good to me, but I'm not an expert in this area, so FWIW a weak:
> 
> Reviewed-by: Thomas Huth <thuth@redhat.com>
>

Patch
diff mbox series

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 871d2e99b156..6ec0685ab2c7 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -4525,21 +4525,28 @@  void kvm_arch_commit_memory_region(struct kvm *kvm,
 				const struct kvm_memory_slot *new,
 				enum kvm_mr_change change)
 {
-	int rc;
+	int rc = 0;
 
-	/* If the basics of the memslot do not change, we do not want
-	 * to update the gmap. Every update causes several unnecessary
-	 * segment translation exceptions. This is usually handled just
-	 * fine by the normal fault handler + gmap, but it will also
-	 * cause faults on the prefix page of running guest CPUs.
-	 */
-	if (old->userspace_addr == mem->userspace_addr &&
-	    old->base_gfn * PAGE_SIZE == mem->guest_phys_addr &&
-	    old->npages * PAGE_SIZE == mem->memory_size)
-		return;
-
-	rc = gmap_map_segment(kvm->arch.gmap, mem->userspace_addr,
-		mem->guest_phys_addr, mem->memory_size);
+	switch (change) {
+	case KVM_MR_DELETE:
+		rc = gmap_unmap_segment(kvm->arch.gmap, old->base_gfn * PAGE_SIZE,
+					old->npages * PAGE_SIZE);
+		break;
+	case KVM_MR_MOVE:
+		rc = gmap_unmap_segment(kvm->arch.gmap, old->base_gfn * PAGE_SIZE,
+					old->npages * PAGE_SIZE);
+		if (rc)
+			break;
+		/* FALLTHROUGH */
+	case KVM_MR_CREATE:
+		rc = gmap_map_segment(kvm->arch.gmap, mem->userspace_addr,
+				      mem->guest_phys_addr, mem->memory_size);
+		break;
+	case KVM_MR_FLAGS_ONLY:
+		break;
+	default:
+		WARN(1, "Unknown KVM MR CHANGE: %d\n", change);
+	}
 	if (rc)
 		pr_warn("failed to commit memory region\n");
 	return;