Hi Marc,
On 4/7/21 7:13 PM, Marc Zyngier wrote:
> On vcpu reset, we expect all the registers to be brought back
> to their initial state, which happens to be a bunch of zeroes.
>
> However, some recent commit broke this, and is now leaving a bunch
> of registers (such as a FP state) with whatever was left by the
> guest. My bad.
>
> Just zero the whole vcpu context on reset. It is more than we
> strictly need, but at least we won't miss anything. This also
> zeroes the __hyp_running_vcpu pointer, which is always NULL
> for a vcpu anyway.
Had a look at struct kvm_cpu_context and indeed the only field which doesn't
represent a guest register is __hyp_running_vcpu. Did a grep for all the places
where __hyp_running_vcpu is used, and indeed the assumption is that for a guest
the pointer is NULL, as __sysreg_restore_el1_state() relies on it.
>
> Cc: stable@xxxxxxxxxxxxxxx
> Fixes: e47c2055c68e ("KVM: arm64: Make struct kvm_regs userspace-only")
> Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
> ---
> arch/arm64/kvm/reset.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
> index bd354cd45d28..ef1c49a1a3ad 100644
> --- a/arch/arm64/kvm/reset.c
> +++ b/arch/arm64/kvm/reset.c
> @@ -240,8 +240,8 @@ int kvm_reset_vcpu(struct kvm_vcpu *vcpu)
> break;
> }
>
> - /* Reset core registers */
> - memset(vcpu_gp_regs(vcpu), 0, sizeof(*vcpu_gp_regs(vcpu)));
> + /* Zero all registers */
> + memset(&vcpu->arch.ctxt, 0, sizeof(vcpu->arch.ctxt));
Checked that code earlier in the function does not touch the guest registers from
vcpu->arch.ctxt, to make sure we're not overwriting other reset values by mistake.
Looks good to me:
Reviewed-by: Alexandru Elisei <alexandru.elisei@xxxxxxx>
Thanks,
Alex
> vcpu_gp_regs(vcpu)->pstate = pstate;
>
> /* Reset system registers */
