Commit 6d56111c authored by Christoffer Dall's avatar Christoffer Dall

KVM: arm/arm64: vgic: Fix GICC_PMR uaccess on GICv3 and clarify ABI

As an oversight, for GICv2, we accidentally export the GICC_PMR register
in the format of the GICH_VMCR.VMPriMask field in the lower 5 bits of a
word, meaning that userspace must always use the lower 5 bits to
communicate with the KVM device and must shift the value left by 3
places to obtain the actual priority mask level.

Since GICv3 supports the full 8 bits of priority masking in the ICH_VMCR,
we have to fix the value we export when emulating a GICv2 on top of a
hardware GICv3 and exporting the emulated GICv2 state to userspace.

Take the chance to clarify this aspect of the ABI.
Reviewed-by: default avatarMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: default avatarChristoffer Dall <cdall@linaro.org>
parent 5b0d2cc2
......@@ -83,6 +83,12 @@ Groups:
Bits for undefined preemption levels are RAZ/WI.
For historical reasons and to provide ABI compatibility with userspace we
export the GICC_PMR register in the format of the GICH_VMCR.VMPriMask
field in the lower 5 bits of a word, meaning that userspace must always
use the lower 5 bits to communicate with the KVM device and must shift the
value left by 3 places to obtain the actual priority mask level.
Limitations:
- Priorities are not implemented, and registers are RAZ/WI
- Currently only implemented for KVM_DEV_TYPE_ARM_VGIC_V2.
......
......@@ -96,6 +96,9 @@
#define GICH_MISR_EOI (1 << 0)
#define GICH_MISR_U (1 << 1)
#define GICV_PMR_PRIORITY_SHIFT 3
#define GICV_PMR_PRIORITY_MASK (0x1f << GICV_PMR_PRIORITY_SHIFT)
#ifndef __ASSEMBLY__
#include <linux/irqdomain.h>
......
......@@ -229,7 +229,15 @@ static unsigned long vgic_mmio_read_vcpuif(struct kvm_vcpu *vcpu,
val = vmcr.ctlr;
break;
case GIC_CPU_PRIMASK:
val = vmcr.pmr;
/*
* Our KVM_DEV_TYPE_ARM_VGIC_V2 device ABI exports the
* the PMR field as GICH_VMCR.VMPriMask rather than
* GICC_PMR.Priority, so we expose the upper five bits of
* priority mask to userspace using the lower bits in the
* unsigned long.
*/
val = (vmcr.pmr & GICV_PMR_PRIORITY_MASK) >>
GICV_PMR_PRIORITY_SHIFT;
break;
case GIC_CPU_BINPOINT:
val = vmcr.bpr;
......@@ -262,7 +270,15 @@ static void vgic_mmio_write_vcpuif(struct kvm_vcpu *vcpu,
vmcr.ctlr = val;
break;
case GIC_CPU_PRIMASK:
vmcr.pmr = val;
/*
* Our KVM_DEV_TYPE_ARM_VGIC_V2 device ABI exports the
* the PMR field as GICH_VMCR.VMPriMask rather than
* GICC_PMR.Priority, so we expose the upper five bits of
* priority mask to userspace using the lower bits in the
* unsigned long.
*/
vmcr.pmr = (val << GICV_PMR_PRIORITY_SHIFT) &
GICV_PMR_PRIORITY_MASK;
break;
case GIC_CPU_BINPOINT:
vmcr.bpr = val;
......
......@@ -206,8 +206,8 @@ void vgic_v2_set_vmcr(struct kvm_vcpu *vcpu, struct vgic_vmcr *vmcrp)
GICH_VMCR_ALIAS_BINPOINT_MASK;
vmcr |= (vmcrp->bpr << GICH_VMCR_BINPOINT_SHIFT) &
GICH_VMCR_BINPOINT_MASK;
vmcr |= (vmcrp->pmr << GICH_VMCR_PRIMASK_SHIFT) &
GICH_VMCR_PRIMASK_MASK;
vmcr |= ((vmcrp->pmr >> GICV_PMR_PRIORITY_SHIFT) <<
GICH_VMCR_PRIMASK_SHIFT) & GICH_VMCR_PRIMASK_MASK;
vcpu->arch.vgic_cpu.vgic_v2.vgic_vmcr = vmcr;
}
......@@ -222,8 +222,8 @@ void vgic_v2_get_vmcr(struct kvm_vcpu *vcpu, struct vgic_vmcr *vmcrp)
GICH_VMCR_ALIAS_BINPOINT_SHIFT;
vmcrp->bpr = (vmcr & GICH_VMCR_BINPOINT_MASK) >>
GICH_VMCR_BINPOINT_SHIFT;
vmcrp->pmr = (vmcr & GICH_VMCR_PRIMASK_MASK) >>
GICH_VMCR_PRIMASK_SHIFT;
vmcrp->pmr = ((vmcr & GICH_VMCR_PRIMASK_MASK) >>
GICH_VMCR_PRIMASK_SHIFT) << GICV_PMR_PRIORITY_SHIFT;
}
void vgic_v2_enable(struct kvm_vcpu *vcpu)
......
......@@ -81,11 +81,18 @@ static inline bool irq_is_pending(struct vgic_irq *irq)
return irq->pending_latch || irq->line_level;
}
/*
* This struct provides an intermediate representation of the fields contained
* in the GICH_VMCR and ICH_VMCR registers, such that code exporting the GIC
* state to userspace can generate either GICv2 or GICv3 CPU interface
* registers regardless of the hardware backed GIC used.
*/
struct vgic_vmcr {
u32 ctlr;
u32 abpr;
u32 bpr;
u32 pmr;
u32 pmr; /* Priority mask field in the GICC_PMR and
* ICC_PMR_EL1 priority field format */
/* Below member variable are valid only for GICv3 */
u32 grpen0;
u32 grpen1;
......
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