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Re: [PATCH v3] s390: kvm: adjust diag318 resets to retain data

From: Christian Borntraeger
Subject: Re: [PATCH v3] s390: kvm: adjust diag318 resets to retain data
Date: Wed, 17 Nov 2021 08:43:39 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.2.0

Am 09.11.21 um 21:56 schrieb Collin Walling:
The CPNC portion of the diag 318 data is erroneously reset during an
initial CPU reset caused by SIGP. Let's go ahead and relocate the
diag318_info field within the CPUS390XState struct such that it is
only zeroed during a clear reset. This way, the CPNC will be retained
for each VCPU in the configuration after the diag 318 instruction
has been invoked.

Signed-off-by: Collin Walling <walling@linux.ibm.com>
Fixes: fabdada9357b ("s390: guest support for diagnose 0x318")
Reported-by: Christian Borntraeger <borntraeger@de.ibm.com>

Reviewed-by: Christian Borntraeger <borntraeger@linux.ibm.com>

maybe add cc stable just in case there will be one.
Can you resend with the final patch description and add Thomas as TO (not cc)
as this should probably go via Thomas tree.


     - handler uses run_on_cpu again
     - reworded commit message slightly
     - added fixes and reported-by tags

     - nixed code reduction changes
     - added a comment to diag318 handler to briefly describe
         when relevent data is zeroed

  target/s390x/cpu.h     | 4 ++--
  target/s390x/kvm/kvm.c | 4 ++++
  2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/target/s390x/cpu.h b/target/s390x/cpu.h
index 3153d053e9..88aace36ff 100644
--- a/target/s390x/cpu.h
+++ b/target/s390x/cpu.h
@@ -63,6 +63,8 @@ struct CPUS390XState {
      uint64_t etoken;       /* etoken */
      uint64_t etoken_extension; /* etoken extension */
+ uint64_t diag318_info;
      /* Fields up to this point are not cleared by initial CPU reset */
      struct {} start_initial_reset_fields;
@@ -118,8 +120,6 @@ struct CPUS390XState {
      uint16_t external_call_addr;
      DECLARE_BITMAP(emergency_signals, S390_MAX_CPUS);
- uint64_t diag318_info;
  #if !defined(CONFIG_USER_ONLY)
      uint64_t tlb_fill_tec;   /* translation exception code during tlb_fill */
      int tlb_fill_exc;        /* exception number seen during tlb_fill */
diff --git a/target/s390x/kvm/kvm.c b/target/s390x/kvm/kvm.c
index 5b1fdb55c4..6acf14d5ec 100644
--- a/target/s390x/kvm/kvm.c
+++ b/target/s390x/kvm/kvm.c
@@ -1585,6 +1585,10 @@ void kvm_s390_set_diag318(CPUState *cs, uint64_t 
          env->diag318_info = diag318_info;
          cs->kvm_run->s.regs.diag318 = diag318_info;
          cs->kvm_run->kvm_dirty_regs |= KVM_SYNC_DIAG318;
+        /*
+         * diag 318 info is zeroed during a clear reset and
+         * diag 308 IPL subcodes.
+         */

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