Re: [PATCH 06/59] KVM: arm64: nv: Allow userspace to set PSR_MODE_EL2x

Julien Thierry
2019-06-21T13:24:57Z

On 21/06/2019 10:37, Marc Zyngier wrote:
> From: Christoffer Dall <christoffer.dall@linaro.org>
>
> We were not allowing userspace to set a more privileged mode for the VCPU
> than EL1, but we should allow this when nested virtualization is enabled
> for the VCPU.
>
> Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
> ---
> arch/arm64/kvm/guest.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c
> index 3ae2f82fca46..4c35b5d51e21 100644
> --- a/arch/arm64/kvm/guest.c
> +++ b/arch/arm64/kvm/guest.c
> @@ -37,6 +37,7 @@
> #include <asm/kvm_emulate.h>
> #include <asm/kvm_coproc.h>
> #include <asm/kvm_host.h>
> +#include <asm/kvm_nested.h>
> #include <asm/sigcontext.h>
>
> #include "trace.h"
> @@ -194,6 +195,11 @@ static int set_core_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
> if (vcpu_el1_is_32bit(vcpu))
> return -EINVAL;
> break;
> + case PSR_MODE_EL2h:
> + case PSR_MODE_EL2t:
> + if (vcpu_el1_is_32bit(vcpu) || !nested_virt_in_use(vcpu))

This condition reads a bit weirdly. Why do we care about anything else
than !nested_virt_in_use() ?

If nested virt is not in use then obviously we return the error.

If nested virt is in use then why do we care about EL1? Or should this
test read as "highest_el_is_32bit" ?

Thanks,

--
Julien Thierry