Hi Marc,
On Fri, Jan 28, 2022 at 12:18:27PM +0000, Marc Zyngier wrote:
> From: Jintack Lim <jintack.lim@xxxxxxxxxx>
>
> For the same reason we trap virtual memory register accesses at virtual
> EL2, we need to trap SPSR_EL1, ELR_EL1 and VBAR_EL1 accesses. ARM v8.3
> introduces the HCR_EL2.NV1 bit to be able to trap on those register
> accesses in EL1. Do not set this bit until the whole nesting support is
> completed.
>
> Signed-off-by: Jintack Lim <jintack.lim@xxxxxxxxxx>
> Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
> ---
> arch/arm64/kvm/sys_regs.c | 29 ++++++++++++++++++++++++++++-
> 1 file changed, 28 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index 9d3520f1d17a..4f2bcc1e0c25 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -1650,6 +1650,30 @@ static bool access_sp_el1(struct kvm_vcpu *vcpu,
> return true;
> }
>
> +static bool access_elr(struct kvm_vcpu *vcpu,
> + struct sys_reg_params *p,
> + const struct sys_reg_desc *r)
> +{
> + if (p->is_write)
> + vcpu_write_sys_reg(vcpu, p->regval, ELR_EL1);
> + else
> + p->regval = vcpu_read_sys_reg(vcpu, ELR_EL1);
Going over the patch again, I was a bit confused why access_elr() uses
vcpu_{read,write}_sys_reg(), but access_spsr() uses __vcpu_sys_reg(). In
the end, vcpu_{read,write}_sys_reg() will write to the shadow copy of the
registers, as the guest is executing at virtual non-VHE EL2, so the two are
equivalent.
It's obviously me nitpicking, but the inconsistency is unexpected. How
about using vcpu_{read,write}_sys_reg() for access_spsr() below?
Thanks,
Alex
> +
> + return true;
> +}
> +
> +static bool access_spsr(struct kvm_vcpu *vcpu,
> + struct sys_reg_params *p,
> + const struct sys_reg_desc *r)
> +{
> + if (p->is_write)
> + __vcpu_sys_reg(vcpu, SPSR_EL1) = p->regval;
> + else
> + p->regval = __vcpu_sys_reg(vcpu, SPSR_EL1);
> +
> + return true;
> +}
> +
> static bool access_spsr_el2(struct kvm_vcpu *vcpu,
> struct sys_reg_params *p,
> const struct sys_reg_desc *r)
> @@ -1812,6 +1836,9 @@ static const struct sys_reg_desc sys_reg_descs[] = {
> PTRAUTH_KEY(APDB),
> PTRAUTH_KEY(APGA),
>
> + { SYS_DESC(SYS_SPSR_EL1), access_spsr},
> + { SYS_DESC(SYS_ELR_EL1), access_elr},
> +
> { SYS_DESC(SYS_AFSR0_EL1), access_vm_reg, reset_unknown, AFSR0_EL1 },
> { SYS_DESC(SYS_AFSR1_EL1), access_vm_reg, reset_unknown, AFSR1_EL1 },
> { SYS_DESC(SYS_ESR_EL1), access_vm_reg, reset_unknown, ESR_EL1 },
> @@ -1859,7 +1886,7 @@ static const struct sys_reg_desc sys_reg_descs[] = {
> { SYS_DESC(SYS_LORC_EL1), trap_loregion },
> { SYS_DESC(SYS_LORID_EL1), trap_loregion },
>
> - { SYS_DESC(SYS_VBAR_EL1), NULL, reset_val, VBAR_EL1, 0 },
> + { SYS_DESC(SYS_VBAR_EL1), access_rw, reset_val, VBAR_EL1, 0 },
> { SYS_DESC(SYS_DISR_EL1), NULL, reset_val, DISR_EL1, 0 },
>
> { SYS_DESC(SYS_ICC_IAR0_EL1), write_to_read_only },
> --
> 2.30.2
>
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