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target-arm: kvm: Differentiate registers based on write-back levels

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Some registers like the CNTVCT register should only be written to the
kernel as part of machine initialization or on vmload operations, but
never during runtime, as this can potentially make time go backwards or
create inconsistent time observations between VCPUs.

Introduce a list of registers that should not be written back at runtime
and check this list on syncing the register state to the KVM state.

Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
Message-id: 1437046488-10773-1-git-send-email-christoffer.dall@linaro.org
[PMM: tweaked a few comments, added the new argument to the stub
 write_list_to_kvmstate() in target-arm/kvm-stub.c]
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
This commit is contained in:
Christoffer Dall 2015-07-21 11:18:45 +01:00 • committed by Peter Maydell
parent a1bc040dab
commit 4b7a6bf402
6 changed files with 76 additions and 6 deletions
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6
target-arm/kvm.c
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@ -409,7 +409,7 @@ bool write_kvmstate_to_list(ARMCPU *cpu)
return ok;
}
bool write_list_to_kvmstate(ARMCPU *cpu)
bool write_list_to_kvmstate(ARMCPU *cpu, int level)
{
CPUState *cs = CPU(cpu);
int i;
@ -421,6 +421,10 @@ bool write_list_to_kvmstate(ARMCPU *cpu)
uint32_t v32;
int ret;
if (kvm_arm_cpreg_level(regidx) > level) {
continue;
}
r.id = regidx;
switch (regidx & KVM_REG_SIZE_MASK) {
case KVM_REG_SIZE_U32: