On 5/22/25 11:31 AM, Christoph Schlameuss wrote:
Instead of allocating a BSCA and upgrading it for PV or when adding the
65th cpu we can always use the ESCA.
The only downside of the change is that we will always allocate 4 pages
for a 248 cpu ESCA instead of a single page for the BSCA per VM.
In return we can delete a bunch of checks and special handling depending
on the SCA type as well as the whole BSCA to ESCA conversion.
As a fallback we can still run without SCA entries when the SIGP
interpretation facility or ESCA are not available.
Signed-off-by: Christoph Schlameuss <schlameuss@xxxxxxxxxxxxx>
---
arch/s390/include/asm/kvm_host.h | 1 -
arch/s390/kvm/interrupt.c | 71 +++++------------
arch/s390/kvm/kvm-s390.c | 161 ++++++---------------------------------
arch/s390/kvm/kvm-s390.h | 4 +-
4 files changed, 45 insertions(+), 192 deletions(-)
diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
index f51bac835260f562eaf4bbfd373a24bfdbc43834..d03e354a63d9c931522c1a1607eba8685c24527f 100644
--- a/arch/s390/include/asm/kvm_host.h
+++ b/arch/s390/include/asm/kvm_host.h
@@ -631,7 +631,6 @@ struct kvm_s390_pv {
[...]
int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
{
- gfp_t alloc_flags = GFP_KERNEL_ACCOUNT;
- int i, rc;
+ gfp_t alloc_flags = GFP_KERNEL_ACCOUNT | __GFP_ZERO;
char debug_name[16];
- static unsigned long sca_offset;
+ int i, rc;
rc = -EINVAL;
#ifdef CONFIG_KVM_S390_UCONTROL
@@ -3358,17 +3341,12 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
if (!sclp.has_64bscao)
alloc_flags |= GFP_DMA;
rwlock_init(&kvm->arch.sca_lock);
- /* start with basic SCA */
- kvm->arch.sca = (struct bsca_block *) get_zeroed_page(alloc_flags);
- if (!kvm->arch.sca)
- goto out_err;
mutex_lock(&kvm_lock);
- sca_offset += 16;
- if (sca_offset + sizeof(struct bsca_block) > PAGE_SIZE)
- sca_offset = 0;
- kvm->arch.sca = (struct bsca_block *)
- ((char *) kvm->arch.sca + sca_offset);
+
+ kvm->arch.sca = alloc_pages_exact(sizeof(*kvm->arch.sca), alloc_flags);
kvm->arch.sca is (void *) at the point of this patch, which makes this a
very bad idea. Granted, you fix that up in the next patch but this is
still wrong.
Any reason why you have patch #3 at all?
We could just squash it and avoid this problem?
mutex_unlock(&kvm_lock);
+ if (!kvm->arch.sca)
+ goto out_err;
sprintf(debug_name, "kvm-%u", current->pid);
[...]
/* needs disabled preemption to protect from TOD sync and vcpu_load/put */
@@ -3919,7 +3808,7 @@ static int kvm_s390_vcpu_setup(struct kvm_vcpu *vcpu)
vcpu->arch.sie_block->eca |= ECA_IB;
if (sclp.has_siif)
vcpu->arch.sie_block->eca |= ECA_SII;
- if (sclp.has_sigpif)
+ if (kvm_s390_use_sca_entries())
vcpu->arch.sie_block->eca |= ECA_SIGPI;
if (test_kvm_facility(vcpu->kvm, 129)) {
vcpu->arch.sie_block->eca |= ECA_VX;
diff --git a/arch/s390/kvm/kvm-s390.h b/arch/s390/kvm/kvm-s390.h
index 8d3bbb2dd8d27802bbde2a7bd1378033ad614b8e..2c8e177e4af8f2dab07fd42a904cefdea80f6855 100644
--- a/arch/s390/kvm/kvm-s390.h
+++ b/arch/s390/kvm/kvm-s390.h
@@ -531,7 +531,7 @@ int kvm_s390_handle_per_event(struct kvm_vcpu *vcpu);
/* support for Basic/Extended SCA handling */
static inline union ipte_control *kvm_s390_get_ipte_control(struct kvm *kvm)
{
- struct bsca_block *sca = kvm->arch.sca; /* SCA version doesn't matter */
+ struct esca_block *sca = kvm->arch.sca; /* SCA version doesn't matter */
Remove the comment as well please
return &sca->ipte_control;
}
@@ -542,7 +542,7 @@ static inline int kvm_s390_use_sca_entries(void)
* might use the entries. By not setting the entries and keeping them
* invalid, hardware will not access them but intercept.
*/
- return sclp.has_sigpif;
+ return sclp.has_sigpif && sclp.has_esca;
}
void kvm_s390_reinject_machine_check(struct kvm_vcpu *vcpu,
struct mcck_volatile_info *mcck_info);
