Hi Marc,
On 2020/4/22 20:00, Marc Zyngier wrote:
Keeping empty structure as the vcpu state initializer is slightly
wasteful: we only want to set pstate, and zero everything else.
Just do that.
Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
---
arch/arm64/kvm/reset.c | 20 +++++++++-----------
1 file changed, 9 insertions(+), 11 deletions(-)
diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
index 241db35a7ef4f..895d7d9ad1866 100644
--- a/arch/arm64/kvm/reset.c
+++ b/arch/arm64/kvm/reset.c
@@ -37,15 +37,11 @@ static u32 kvm_ipa_limit;
/*
* ARMv8 Reset Values
*/
-static const struct kvm_regs default_regs_reset = {
- .regs.pstate = (PSR_MODE_EL1h | PSR_A_BIT | PSR_I_BIT |
- PSR_F_BIT | PSR_D_BIT),
-};
+#define VCPU_RESET_PSTATE_EL1 (PSR_MODE_EL1h | PSR_A_BIT | PSR_I_BIT | \
+ PSR_F_BIT | PSR_D_BIT)
-static const struct kvm_regs default_regs_reset32 = {
- .regs.pstate = (PSR_AA32_MODE_SVC | PSR_AA32_A_BIT |
- PSR_AA32_I_BIT | PSR_AA32_F_BIT),
-};
+#define VCPU_RESET_PSTATE_SVC (PSR_AA32_MODE_SVC | PSR_AA32_A_BIT | \
+ PSR_AA32_I_BIT | PSR_AA32_F_BIT)
static bool cpu_has_32bit_el1(void)
{
@@ -261,6 +257,7 @@ int kvm_reset_vcpu(struct kvm_vcpu *vcpu)
const struct kvm_regs *cpu_reset;
int ret = -EINVAL;
bool loaded;
+ u32 pstate;
/* Reset PMU outside of the non-preemptible section */
kvm_pmu_vcpu_reset(vcpu);
@@ -291,16 +288,17 @@ int kvm_reset_vcpu(struct kvm_vcpu *vcpu)
if (test_bit(KVM_ARM_VCPU_EL1_32BIT, vcpu->arch.features)) {
if (!cpu_has_32bit_el1())
goto out;
- cpu_reset = &default_regs_reset32;
+ pstate = VCPU_RESET_PSTATE_SVC;
} else {
- cpu_reset = &default_regs_reset;
+ pstate = VCPU_RESET_PSTATE_EL1;
}
break;
}
/* Reset core registers */
- memcpy(vcpu_gp_regs(vcpu), cpu_reset, sizeof(*cpu_reset));
+ memset(vcpu_gp_regs(vcpu), 0, sizeof(*cpu_reset));
Be careful that we can *not* use 'sizeof(*cpu_reset)' here anymore. As
you're going to refactor the layout of the core registers whilst keeping
the kvm_regs API unchanged. Resetting the whole kvm_regs will go
corrupting some affected registers and make them temporarily invalid.
The bad thing will show up after you start moving ELR_EL1 around,
specifically in patch #20...
And the first victim is ... MPIDR_EL1 (the first one in sys_regs array).
Now you know how this was spotted ;-) I think this should be the root
cause of what Zengtao had previously reported [*].
If these registers are all expected to be reset to architecturally
UNKNOWN values, I think we can just drop this memset(), though haven't
check with the ARM ARM carefully.
Thanks,
Zenghui
[*]
https://lore.kernel.org/kvmarm/f55386a9-8eaa-944f-453d-9c3c4abee5fb@xxxxxxx/T/#mc6c7268755f5cdaff7a23c34e6e16ea36bcfbe22
+ vcpu_gp_regs(vcpu)->regs.pstate = pstate;
/* Reset system registers */
kvm_reset_sys_regs(vcpu);
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