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Mon, 10 Nov 2025 17:17:38 +0000 (GMT) From: Christoph Schlameuss Date: Mon, 10 Nov 2025 18:16:50 +0100 Subject: [PATCH RFC v2 10/11] KVM: s390: Add VSIE shadow configuration Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20251110-vsieie-v2-10-9e53a3618c8c@linux.ibm.com> References: <20251110-vsieie-v2-0-9e53a3618c8c@linux.ibm.com> In-Reply-To: <20251110-vsieie-v2-0-9e53a3618c8c@linux.ibm.com> To: kvm@vger.kernel.org Cc: linux-s390@vger.kernel.org, Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Christian Borntraeger , Janosch Frank , Claudio Imbrenda , Nico Boehr , David Hildenbrand , Sven Schnelle , Paolo Bonzini , Shuah Khan , Christoph Schlameuss X-Mailer: b4 0.14.2 X-Developer-Signature: v=1; a=openpgp-sha256; l=3166; i=schlameuss@linux.ibm.com; h=from:subject:message-id; bh=OqkuoFkh+DNCH2GM1okMh1NF5heTrlG9iNrW/OksDos=; 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KVM will use the maximum of the current number of vCPUs and a maximum of 256 or this value if it is lower. This is the number of guest-3 control blocks / CPUs to keep shadowed to minimize the repeated shadowing effort. * vsie_shadow_sca_max Override the maximum number of VSIE system control areas to shadow in guest-1. KVM will use a minimum of the current number of vCPUs and a maximum of 256 or this value if it is lower. This is the number of guest-3 system control areas / VMs to keep shadowed to minimize repeated shadowing effort. Signed-off-by: Christoph Schlameuss --- arch/s390/kvm/vsie.c | 18 +++++++++++++++--- 1 file changed, 15 insertions(+), 3 deletions(-) diff --git a/arch/s390/kvm/vsie.c b/arch/s390/kvm/vsie.c index b69ef763b55296875522f2e63169446b5e2d5053..cd114df5e119bd289d14037d1f1c5bfe148cf5c7 100644 --- a/arch/s390/kvm/vsie.c +++ b/arch/s390/kvm/vsie.c @@ -98,9 +98,19 @@ struct vsie_sca { struct vsie_page *pages[KVM_S390_MAX_VSIE_VCPUS]; }; +/* maximum vsie shadow scb */ +unsigned int vsie_shadow_scb_max; +module_param(vsie_shadow_scb_max, uint, 0644); +MODULE_PARM_DESC(vsie_shadow_scb_max, "Maximum number of VSIE shadow control blocks to keep. Values smaller number vcpus uses number of vcpus; maximum 256"); + +/* maximum vsie shadow sca */ +unsigned int vsie_shadow_sca_max; +module_param(vsie_shadow_sca_max, uint, 0644); +MODULE_PARM_DESC(vsie_shadow_sca_max, "Maximum number of VSIE shadow system control areas to keep. Values smaller number of vcpus uses number of vcpus; 0 to disable sca shadowing; maximum 256"); + static inline bool use_vsie_sigpif(struct kvm *kvm) { - return kvm->arch.use_vsie_sigpif; + return kvm->arch.use_vsie_sigpif && vsie_shadow_sca_max; } static inline bool use_vsie_sigpif_for(struct kvm *kvm, struct vsie_page *vsie_page) @@ -907,7 +917,8 @@ static struct vsie_sca *get_vsie_sca(struct kvm_vcpu *vcpu, struct vsie_page *vs * We want at least #online_vcpus shadows, so every VCPU can execute the * VSIE in parallel. (Worst case all single core VMs.) */ - max_sca = MIN(atomic_read(&kvm->online_vcpus), KVM_S390_MAX_VSIE_VCPUS); + max_sca = MIN(MAX(atomic_read(&kvm->online_vcpus), vsie_shadow_sca_max), + KVM_S390_MAX_VSIE_VCPUS); if (kvm->arch.vsie.sca_count < max_sca) { BUILD_BUG_ON(sizeof(struct vsie_sca) > PAGE_SIZE); sca_new = (void *)__get_free_page(GFP_KERNEL_ACCOUNT | __GFP_ZERO); @@ -1782,7 +1793,8 @@ static struct vsie_page *get_vsie_page(struct kvm_vcpu *vcpu, unsigned long addr put_vsie_page(vsie_page); } - max_vsie_page = MIN(atomic_read(&kvm->online_vcpus), KVM_S390_MAX_VSIE_VCPUS); + max_vsie_page = MIN(MAX(atomic_read(&kvm->online_vcpus), vsie_shadow_scb_max), + KVM_S390_MAX_VSIE_VCPUS); /* allocate new vsie_page - we will likely need it */ if (addr || kvm->arch.vsie.page_count < max_vsie_page) { -- 2.51.1