On Mon, Nov 29, 2021 at 08:00:49PM +0000, Marc Zyngier wrote:
> From: Christoffer Dall <christoffer.dall@xxxxxxx>
>
> Reset the VCPU with PSTATE.M = EL2h when the nested virtualization
> feature is enabled on the VCPU.
>
> Signed-off-by: Christoffer Dall <christoffer.dall@xxxxxxx>
> [maz: rework register reset not to use empty data structures]
> Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
Reviewed-by: Russell King (Oracle) <rmk+kernel@xxxxxxxxxxxxxxx>
However, a couple of comments below.
> ---
> arch/arm64/kvm/reset.c | 10 ++++++++--
> 1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
> index 426bd7fbc3fd..38a7182819fb 100644
> --- a/arch/arm64/kvm/reset.c
> +++ b/arch/arm64/kvm/reset.c
> @@ -27,6 +27,7 @@
> #include <asm/kvm_asm.h>
> #include <asm/kvm_emulate.h>
> #include <asm/kvm_mmu.h>
> +#include <asm/kvm_nested.h>
> #include <asm/virt.h>
>
> /* Maximum phys_shift supported for any VM on this host */
> @@ -38,6 +39,9 @@ static u32 kvm_ipa_limit;
> #define VCPU_RESET_PSTATE_EL1 (PSR_MODE_EL1h | PSR_A_BIT | PSR_I_BIT | \
> PSR_F_BIT | PSR_D_BIT)
>
> +#define VCPU_RESET_PSTATE_EL2 (PSR_MODE_EL2h | PSR_A_BIT | PSR_I_BIT | \
> + PSR_F_BIT | PSR_D_BIT)
> +
> #define VCPU_RESET_PSTATE_SVC (PSR_AA32_MODE_SVC | PSR_AA32_A_BIT | \
> PSR_AA32_I_BIT | PSR_AA32_F_BIT)
>
> @@ -176,8 +180,8 @@ static bool vcpu_allowed_register_width(struct kvm_vcpu *vcpu)
> if (!cpus_have_const_cap(ARM64_HAS_32BIT_EL1) && is32bit)
> return false;
>
> - /* MTE is incompatible with AArch32 */
> - if (kvm_has_mte(vcpu->kvm) && is32bit)
> + /* MTE and NV are incompatible with AArch32 */
> + if ((kvm_has_mte(vcpu->kvm) || nested_virt_in_use(vcpu)) && is32bit)
> return false;
It seems we have a bunch of:
if (something && is32bit)
return false;
tests here - would it make sense to do:
if (is32bit) {
if (!cpus_have_const_cap(ARM64_HAS_32BIT_EL1))
return false;
/* MTE is incompatible with AArch32 */
if (kvm_has_mte(vcpu->kvm))
return false;
/* NV is incompatible with AArch32 */
if (nested_virt_in_use(vcpu))
return false;
}
in terms of improved readability?
> @@ -255,6 +259,8 @@ int kvm_reset_vcpu(struct kvm_vcpu *vcpu)
> default:
> if (test_bit(KVM_ARM_VCPU_EL1_32BIT, vcpu->arch.features)) {
> pstate = VCPU_RESET_PSTATE_SVC;
> + } else if (nested_virt_in_use(vcpu)) {
> + pstate = VCPU_RESET_PSTATE_EL2;
> } else {
> pstate = VCPU_RESET_PSTATE_EL1;
> }
Not an issue with your patch, but the switch around this looks useless.
The only case is this default case, so it's entirely a no-op.
--
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