2024-05-14 07:23:33

by Sebastian Ott

Subject: [PATCH v3 4/6] KVM: arm64: show writable masks for feature registers

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.

This changes the mask for the CTR_EL0 and CLIDR_EL1 registers.

Signed-off-by: Sebastian Ott <[email protected]>
---
arch/arm64/kvm/sys_regs.c | 19 +++++--------------
1 file changed, 5 insertions(+), 14 deletions(-)

diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 8e8acf3dd9bd..1b6ab483e21e 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -2562,7 +2562,7 @@ 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 = ~CLIDR_EL1_RES0 },
{ 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 },
@@ -4121,20 +4121,11 @@ 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_vm_ftr_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;

if (put_user(val, (masks + KVM_ARM_FEATURE_ID_RANGE_INDEX(encoding))))
return -EFAULT;
--
2.42.0

2024-05-29 13:49:55

by Eric Auger

Subject: Re: [PATCH v3 4/6] KVM: arm64: show writable masks for feature registers

Hi Sebastian,

On 5/14/24 09:22, Sebastian Ott 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.
>
> This changes the mask for the CTR_EL0 and CLIDR_EL1 registers.
>
> Signed-off-by: Sebastian Ott <[email protected]>
> ---
> arch/arm64/kvm/sys_regs.c | 19 +++++--------------
> 1 file changed, 5 insertions(+), 14 deletions(-)
>
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index 8e8acf3dd9bd..1b6ab483e21e 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -2562,7 +2562,7 @@ 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 = ~CLIDR_EL1_RES0 },
> { 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 },
> @@ -4121,20 +4121,11 @@ 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_vm_ftr_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;
>
> if (put_user(val, (masks + KVM_ARM_FEATURE_ID_RANGE_INDEX(encoding))))
> return -EFAULT;
Reviewed-by: Eric Auger <[email protected]>

Eric