On Wed, May 03 2023, Jing Zhang <jingzhangos@xxxxxxxxxx> wrote:
> Since reset() and val are not used for idreg in sys_reg_desc, they would
> be used with other purposes for idregs.
> The callback reset() would be used to return KVM sanitised id register
> values. The u64 val would be used as mask for writable fields in idregs.
> Only bits with 1 in val are writable from userspace.
>
> Signed-off-by: Jing Zhang <jingzhangos@xxxxxxxxxx>
> ---
> arch/arm64/kvm/id_regs.c | 44 +++++++++++++++++++----------
> arch/arm64/kvm/sys_regs.c | 59 +++++++++++++++++++++++++++------------
> arch/arm64/kvm/sys_regs.h | 10 ++++---
> 3 files changed, 77 insertions(+), 36 deletions(-)
>
(...)
> diff --git a/arch/arm64/kvm/sys_regs.h b/arch/arm64/kvm/sys_regs.h
> index e88fd77309b2..21869319f6e1 100644
> --- a/arch/arm64/kvm/sys_regs.h
> +++ b/arch/arm64/kvm/sys_regs.h
> @@ -65,12 +65,12 @@ struct sys_reg_desc {
> const struct sys_reg_desc *);
>
> /* Initialization for vcpu. */
Maybe be a bit more verbose here?
/* Initialization for vcpu. Return initialized value, or KVM sanitized
value for id registers. */
> - void (*reset)(struct kvm_vcpu *, const struct sys_reg_desc *);
> + u64 (*reset)(struct kvm_vcpu *, const struct sys_reg_desc *);
>
> /* Index into sys_reg[], or 0 if we don't need to save it. */
> int reg;
>
> - /* Value (usually reset value) */
> + /* Value (usually reset value), or write mask for idregs */
> u64 val;
>
> /* Custom get/set_user functions, fallback to generic if NULL */
