Re: [PATCH 16/21] KVM: s390: vsie: Shadow VSIE SCA in guest-1

[Janosch Frank <frankja@linux.ibm.com>]

On 7/9/26 17:15, Christoph Schlameuss wrote:
> Restructure kvm_s390_handle_vsie() to create a guest-1 shadow of the SCA
> if guest-2 attempts to enter SIE with an SCA. If the SCA is used the
> vsie_pages are stored in a new vsie_sca struct instead of the arch vsie
> struct.
> 
> When the VSIE-Interpretation-Extension Facility is active the shadow SCA
> (ssca_block) will be created and shadows of all CPUs defined in the
> configuration are created. SCAOL/H in the VSIE control block are
> overwritten with references to the shadow SCA.
> 
> The shadow SCA contains the addresses of the original guest-3 SCA as
> well as the original VSIE control blocks. With these addresses the
> machine can directly monitor the intervention bits within the original
> SCA entries, enabling it to handle SENSE_RUNNING and EXTERNAL_CALL sigp
> instructions without exiting VSIE.
> 
> The original SCA will be pinned in guest-2 memory and only be unpinned
> before reuse. This means some pages might still be pinned even after the
> guest 3 VM does no longer exist.
> 
> The vsie_scas including the ssca_blocks are also kept within a map to
> reuse already existing ssca_blocks efficiently. While the map and array
> with references to the vsie_scas are held in the arch vsie struct. The
> use of vsie_scas is tracked using an ref_count.
> 
> Signed-off-by: Christoph Schlameuss <schlameuss@linux.ibm.com>
> ---

[...]

> +/*
> + * Try to find the address of an existing shadow system control area.
> + * @sca_o_gpa: original system control area address; guest-2 physical
> + *
> + * Called with lock on vsie_sca_lock.
> + */
> +static struct vsie_sca *get_existing_vsie_sca(struct kvm *kvm, hpa_t sca_o_gpa)
> +{
> +	struct vsie_sca *vsie_sca = xa_load(&kvm->arch.vsie.osca_to_sca, sca_o_gpa >> 6);

s/6/SSCA_ALIGNMENT_SHIFT/