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hw/s390x/s390-skeys: lazy storage key enablement under TCG

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Let's enable storage keys lazily under TCG, just as we do under KVM.
Only fairly old Linux versions actually make use of storage keys, so it
can be kind of wasteful to allocate quite some memory and track
changes and references if nobody cares.

We have to make sure to flush the TLB when enabling storage keys after
the VM was already running: otherwise it might happen that we don't
catch references or modifications afterwards.

Add proper documentation to all callbacks.

The kvm-unit-tests skey tests keeps on working with this change.

Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Message-Id: <20210903155514.44772-14-david@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
This commit is contained in:
David Hildenbrand 2021-09-03 17:55:14 +02:00 • committed by Thomas Huth
parent 5227b32601
commit c35622387e
4 changed files with 134 additions and 17 deletions
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9
target/s390x/tcg/mem_helper.c
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@ -2186,6 +2186,9 @@ uint64_t HELPER(iske)(CPUS390XState *env, uint64_t r2)
if (unlikely(!ss)) {
ss = s390_get_skeys_device();
skeyclass = S390_SKEYS_GET_CLASS(ss);
if (skeyclass->enable_skeys && !skeyclass->enable_skeys(ss)) {
tlb_flush_all_cpus_synced(env_cpu(env));
}
}
rc = skeyclass->get_skeys(ss, addr / TARGET_PAGE_SIZE, 1, &key);
@ -2213,6 +2216,9 @@ void HELPER(sske)(CPUS390XState *env, uint64_t r1, uint64_t r2)
if (unlikely(!ss)) {
ss = s390_get_skeys_device();
skeyclass = S390_SKEYS_GET_CLASS(ss);
if (skeyclass->enable_skeys && !skeyclass->enable_skeys(ss)) {
tlb_flush_all_cpus_synced(env_cpu(env));
}
}
key = r1 & 0xfe;
@ -2244,6 +2250,9 @@ uint32_t HELPER(rrbe)(CPUS390XState *env, uint64_t r2)
if (unlikely(!ss)) {
ss = s390_get_skeys_device();
skeyclass = S390_SKEYS_GET_CLASS(ss);
if (skeyclass->enable_skeys && !skeyclass->enable_skeys(ss)) {
tlb_flush_all_cpus_synced(env_cpu(env));
}
}
rc = skeyclass->get_skeys(ss, addr / TARGET_PAGE_SIZE, 1, &key);