Re: [PATCH v10 2/3] KVM: s390: guest support for topology function

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On 6/24/22 11:32, Claudio Imbrenda wrote:
On Mon, 20 Jun 2022 14:54:36 +0200
Pierre Morel <pmorel@xxxxxxxxxxxxx> wrote:

We report a topology change to the guest for any CPU hotplug.

The reporting to the guest is done using the Multiprocessor
Topology-Change-Report (MTCR) bit of the utility entry in the guest's
SCA which will be cleared during the interpretation of PTF.

On every vCPU creation we set the MCTR bit to let the guest know the
next time he uses the PTF with command 2 instruction that the
topology changed and that he should use the STSI(15.1.x) instruction
to get the topology details.

STSI(15.1.x) gives information on the CPU configuration topology.
Let's accept the interception of STSI with the function code 15 and
let the userland part of the hypervisor handle it when userland
support the CPU Topology facility.

Signed-off-by: Pierre Morel <pmorel@xxxxxxxxxxxxx>
---
  arch/s390/include/asm/kvm_host.h | 11 ++++++++---
  arch/s390/kvm/kvm-s390.c         | 27 ++++++++++++++++++++++++++-
  arch/s390/kvm/priv.c             | 15 +++++++++++----
  arch/s390/kvm/vsie.c             |  3 +++
  4 files changed, 48 insertions(+), 8 deletions(-)

diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
index 766028d54a3e..bb54196d4ed6 100644
--- a/arch/s390/include/asm/kvm_host.h
+++ b/arch/s390/include/asm/kvm_host.h
@@ -97,15 +97,19 @@ struct bsca_block {
  	union ipte_control ipte_control;
  	__u64	reserved[5];
  	__u64	mcn;
-	__u64	reserved2;
+#define SCA_UTILITY_MTCR	0x8000
+	__u16	utility;
+	__u8	reserved2[6];
  	struct bsca_entry cpu[KVM_S390_BSCA_CPU_SLOTS];
  };
struct esca_block {
  	union ipte_control ipte_control;
-	__u64   reserved1[7];
+	__u64   reserved1[6];
+	__u16	utility;
+	__u8	reserved2[6];
  	__u64   mcn[4];
-	__u64   reserved2[20];
+	__u64   reserved3[20];
  	struct esca_entry cpu[KVM_S390_ESCA_CPU_SLOTS];
  };
@@ -249,6 +253,7 @@ struct kvm_s390_sie_block {
  #define ECB_SPECI	0x08
  #define ECB_SRSI	0x04
  #define ECB_HOSTPROTINT	0x02
+#define ECB_PTF		0x01
  	__u8	ecb;			/* 0x0061 */
  #define ECB2_CMMA	0x80
  #define ECB2_IEP	0x20
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 8fcb56141689..95b96019ca8e 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -1691,6 +1691,25 @@ static int kvm_s390_get_cpu_model(struct kvm *kvm, struct kvm_device_attr *attr)
  	return ret;
  }
+/**
+ * kvm_s390_sca_set_mtcr

the format for kdoc is:

	function_name - very short description

please add a very short description. something like:

	kvm_s390_sca_set_mtcr - update mtcr to signal topology change


OK, thanks,

Pierre

--
Pierre Morel
IBM Lab Boeblingen



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