diff mbox series

[v2,06/11] KVM: arm64: hide MOPS from guests

Message ID 20230509142235.3284028-7-kristina.martsenko@arm.com
State New
Headers
Series arm64: Support for Armv8.8 memcpy instructions in userspace |

Commit Message

Kristina Martsenko May 9, 2023, 2:22 p.m. UTC 
  As FEAT_MOPS is not supported in guests yet, hide it from the ID
registers for guests.

The MOPS instructions are UNDEFINED in guests as HCRX_EL2.MSCEn is not
set in HCRX_GUEST_FLAGS, and will take an exception to EL1 if executed.

Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Kristina Martsenko <kristina.martsenko@arm.com>
---
 arch/arm64/kvm/sys_regs.c | 1 +
 1 file changed, 1 insertion(+)

Comments

Colton Lewis May 25, 2023, 7:26 p.m. UTC | #1 
> As FEAT_MOPS is not supported in guests yet, hide it from the ID
> registers for guests.

> The MOPS instructions are UNDEFINED in guests as HCRX_EL2.MSCEn is not
> set in HCRX_GUEST_FLAGS, and will take an exception to EL1 if executed.

For my benefit, could you please explain why no support for guests yet?
Why not set HCRX_EL2.MSCEn in this series?
Kristina Martsenko May 30, 2023, 4:34 p.m. UTC | #2 
On 25/05/2023 20:26, Colton Lewis wrote:
>> As FEAT_MOPS is not supported in guests yet, hide it from the ID
>> registers for guests.
> 
>> The MOPS instructions are UNDEFINED in guests as HCRX_EL2.MSCEn is not
>> set in HCRX_GUEST_FLAGS, and will take an exception to EL1 if executed.
> 
> For my benefit, could you please explain why no support for guests yet?
> Why not set HCRX_EL2.MSCEn in this series?

There's probably a few more things that need doing for guest support, such as 
setting the HCRX_EL2.MCE2 bit and handling the mops exception in KVM. I'm
currently having a look at guest support.

Thanks,
Kristina
Marc Zyngier June 3, 2023, 8:42 a.m. UTC | #3 
On Tue, 09 May 2023 15:22:30 +0100,
Kristina Martsenko <kristina.martsenko@arm.com> wrote:
> 
> As FEAT_MOPS is not supported in guests yet, hide it from the ID
> registers for guests.
> 
> The MOPS instructions are UNDEFINED in guests as HCRX_EL2.MSCEn is not
> set in HCRX_GUEST_FLAGS, and will take an exception to EL1 if executed.
> 
> Acked-by: Catalin Marinas <catalin.marinas@arm.com>
> Signed-off-by: Kristina Martsenko <kristina.martsenko@arm.com>

This is very likely to clash with Jing's series that completely
reworks the whole idreg series, but as long as this is on its own
branch, we can deal with that.

Acked-by: Marc Zyngier <maz@kernel.org>

	M.
Oliver Upton June 5, 2023, 3:45 p.m. UTC | #4 
On Sat, Jun 03, 2023 at 09:42:18AM +0100, Marc Zyngier wrote:
> On Tue, 09 May 2023 15:22:30 +0100,
> Kristina Martsenko <kristina.martsenko@arm.com> wrote:
> > 
> > As FEAT_MOPS is not supported in guests yet, hide it from the ID
> > registers for guests.
> > 
> > The MOPS instructions are UNDEFINED in guests as HCRX_EL2.MSCEn is not
> > set in HCRX_GUEST_FLAGS, and will take an exception to EL1 if executed.
> > 
> > Acked-by: Catalin Marinas <catalin.marinas@arm.com>
> > Signed-off-by: Kristina Martsenko <kristina.martsenko@arm.com>
> 
> This is very likely to clash with Jing's series that completely
> reworks the whole idreg series, but as long as this is on its own
> branch, we can deal with that.

Yup, we will definitely want to get that ironed out. I'll pull Catalin's
branch when this all gets queued up.

Acked-by: Oliver Upton <oliver.upton@linux.dev>
diff mbox series

Patch

diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 71b12094d613..6dae7fe91cfa 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1252,6 +1252,7 @@  static u64 read_id_reg(const struct kvm_vcpu *vcpu, struct sys_reg_desc const *r
 				 ARM64_FEATURE_MASK(ID_AA64ISAR2_EL1_GPA3));
 		if (!cpus_have_final_cap(ARM64_HAS_WFXT))
 			val &= ~ARM64_FEATURE_MASK(ID_AA64ISAR2_EL1_WFxT);
+		val &= ~ARM64_FEATURE_MASK(ID_AA64ISAR2_EL1_MOPS);
 		break;
 	case SYS_ID_AA64DFR0_EL1:
 		/* Limit debug to ARMv8.0 */