[PATCH 3/4] KVM: arm64: show writable masks for feature registers
Marc Zyngier
maz at kernel.org
Mon Mar 18 05:03:04 PDT 2024
On Mon, 18 Mar 2024 11:16:35 +0000,
Sebastian Ott <sebott at redhat.com> wrote:
>
> Instead of using ~0UL provide the actual writable mask for
> non-id feature registers in the output of the
> KVM_ARM_GET_REG_WRITABLE_MASKS ioctl.
CTR_EL0 definitely seems to be in the feature ID range. And so does
CLIDR_EL1.
>
> This changes the mask for the CTR_EL0 register.
Only that?
>
> Signed-off-by: Sebastian Ott <sebott at redhat.com>
> ---
> arch/arm64/kvm/sys_regs.c | 21 ++++++---------------
> 1 file changed, 6 insertions(+), 15 deletions(-)
>
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index b2019faa9d73..0f8fe7790c35 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -2489,12 +2489,12 @@ static const struct sys_reg_desc sys_reg_descs[] = {
>
> { SYS_DESC(SYS_CCSIDR_EL1), access_ccsidr },
> { SYS_DESC(SYS_CLIDR_EL1), access_clidr, reset_clidr, CLIDR_EL1,
> - .set_user = set_clidr },
> + .set_user = set_clidr, .val = ~0UL },
How is CLIDR_EL1 (and all the crap that depend on it) recomputed when
CTR_EL0 is changed?
> { SYS_DESC(SYS_CCSIDR2_EL1), undef_access },
> { SYS_DESC(SYS_SMIDR_EL1), undef_access },
> { SYS_DESC(SYS_CSSELR_EL1), access_csselr, reset_unknown, CSSELR_EL1 },
> { SYS_DESC(SYS_CTR_EL0), access_ctr, .reset = reset_ctr,
> - .get_user = get_ctr, .set_user = set_ctr},
> + .get_user = get_ctr, .set_user = set_ctr, .val = CTR_EL0_DIC_MASK},
This is all extremely fragile. We need a better solution for this. And
we need far more than just DIC here.
> { SYS_DESC(SYS_SVCR), undef_access },
>
> { PMU_SYS_REG(PMCR_EL0), .access = access_pmcr, .reset = reset_pmcr,
> @@ -3934,20 +3934,11 @@ int kvm_vm_ioctl_get_reg_writable_masks(struct kvm *kvm, struct reg_mask_range *
> if (!is_feature_id_reg(encoding) || !reg->set_user)
> continue;
>
> - /*
> - * For ID registers, we return the writable mask. Other feature
> - * registers return a full 64bit mask. That's not necessary
> - * compliant with a given revision of the architecture, but the
> - * RES0/RES1 definitions allow us to do that.
> - */
> - if (is_id_reg(encoding)) {
> - if (!reg->val ||
> - (is_aa32_id_reg(encoding) && !kvm_supports_32bit_el0()))
> - continue;
> - val = reg->val;
> - } else {
> - val = ~0UL;
> + if (!reg->val ||
> + (is_aa32_id_reg(encoding) && !kvm_supports_32bit_el0())) {
> + continue;
> }
> + val = reg->val;
Are CLIDR_EL1 and CTR_EL0 the only two ID registers that had a
set_user callback without an encoded mask?
M.
--
Without deviation from the norm, progress is not possible.
More information about the linux-arm-kernel
mailing list