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From: Alexandru Elisei <alexandru.elisei@arm.com>
To: Eric Auger <eric.auger@redhat.com>,
	eric.auger.pro@gmail.com, linux-kernel@vger.kernel.org,
	kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu,
	maz@kernel.org, drjones@redhat.com
Cc: james.morse@arm.com, julien.thierry.kdev@gmail.com,
	suzuki.poulose@arm.com, shuah@kernel.org, pbonzini@redhat.com
Subject: Re: [PATCH 8/9] KVM: arm64: vgic-v3: Expose GICR_TYPER.Last for userspace
Date: Tue, 12 Jan 2021 17:28:52 +0000	[thread overview]
Message-ID: <fe0a3415-0c7b-be13-6438-89e82fe4c281@arm.com> (raw)
In-Reply-To: <20201212185010.26579-9-eric.auger@redhat.com>

Hi Eric,

On 12/12/20 6:50 PM, Eric Auger wrote:
> Commit 23bde34771f1 ("KVM: arm64: vgic-v3: Drop the
> reporting of GICR_TYPER.Last for userspace") temporarily fixed
> a bug identified when attempting to access the GICR_TYPER
> register before the redistributor region setting but dropped
> the support of the LAST bit. This patch restores its
> support (if the redistributor region was set) while keeping the
> code safe.

If I understand your patch correctly, it is possible for the GICR_TYPER.Last bit
to be transiently 1 if the register is accessed before all the redistributors
regions have been configured.

Arm IHI 0069F states that accesses to the GICR_TYPER register are RO. I haven't
found exactly what RO means (please point me to the definition if you find it in
the architecture!), but I assume it means read-only and I'm not sure how correct
(from an architectural point of view) it is for two subsequent reads of this
register to return different values. Maybe Marc can shed some light on this.

Thanks,
Alex
>
> Signed-off-by: Eric Auger <eric.auger@redhat.com>
> ---
>  arch/arm64/kvm/vgic/vgic-mmio-v3.c | 7 ++++++-
>  include/kvm/arm_vgic.h             | 1 +
>  2 files changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/kvm/vgic/vgic-mmio-v3.c b/arch/arm64/kvm/vgic/vgic-mmio-v3.c
> index 581f0f490000..2f9ef6058f6e 100644
> --- a/arch/arm64/kvm/vgic/vgic-mmio-v3.c
> +++ b/arch/arm64/kvm/vgic/vgic-mmio-v3.c
> @@ -277,6 +277,8 @@ static unsigned long vgic_uaccess_read_v3r_typer(struct kvm_vcpu *vcpu,
>  						 gpa_t addr, unsigned int len)
>  {
>  	unsigned long mpidr = kvm_vcpu_get_mpidr_aff(vcpu);
> +	struct vgic_cpu *vgic_cpu = &vcpu->arch.vgic_cpu;
> +	struct vgic_redist_region *rdreg = vgic_cpu->rdreg;
>  	int target_vcpu_id = vcpu->vcpu_id;
>  	u64 value;
>  
> @@ -286,7 +288,9 @@ static unsigned long vgic_uaccess_read_v3r_typer(struct kvm_vcpu *vcpu,
>  	if (vgic_has_its(vcpu->kvm))
>  		value |= GICR_TYPER_PLPIS;
>  
> -	/* reporting of the Last bit is not supported for userspace */
> +	if (rdreg && (vgic_cpu->rdreg_index == (rdreg->free_index - 1)))
> +		value |= GICR_TYPER_LAST;
> +
>  	return extract_bytes(value, addr & 7, len);
>  }
>  
> @@ -714,6 +718,7 @@ int vgic_register_redist_iodev(struct kvm_vcpu *vcpu)
>  		return -EINVAL;
>  
>  	vgic_cpu->rdreg = rdreg;
> +	vgic_cpu->rdreg_index = rdreg->free_index;
>  
>  	rd_base = rdreg->base + rdreg->free_index * KVM_VGIC_V3_REDIST_SIZE;
>  
> diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
> index a8d8fdcd3723..596c069263a7 100644
> --- a/include/kvm/arm_vgic.h
> +++ b/include/kvm/arm_vgic.h
> @@ -322,6 +322,7 @@ struct vgic_cpu {
>  	 */
>  	struct vgic_io_device	rd_iodev;
>  	struct vgic_redist_region *rdreg;
> +	u32 rdreg_index;
>  
>  	/* Contains the attributes and gpa of the LPI pending tables. */
>  	u64 pendbaser;

  parent reply	other threads:[~2021-01-12 17:29 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-12 18:50 [PATCH 0/9] KVM/ARM: Some vgic fixes and init sequence KVM selftests Eric Auger
2020-12-12 18:50 ` [PATCH 1/9] KVM: arm64: vgic-v3: Fix some error codes when setting RDIST base Eric Auger
2021-01-06 16:32   ` Alexandru Elisei
2021-01-14 10:02     ` Auger Eric
2020-12-12 18:50 ` [PATCH 2/9] KVM: arm64: Fix KVM_VGIC_V3_ADDR_TYPE_REDIST_REGION read Eric Auger
2021-01-06 17:12   ` Alexandru Elisei
2021-01-13 17:18     ` Auger Eric
2020-12-12 18:50 ` [PATCH 3/9] KVM: arm64: vgic-v3: Fix error handling in vgic_v3_set_redist_base() Eric Auger
2020-12-28 15:35   ` Marc Zyngier
2021-01-13 17:18     ` Auger Eric
2020-12-12 18:50 ` [PATCH 4/9] KVM: arm/arm64: vgic: Reset base address on kvm_vgic_dist_destroy() Eric Auger
2020-12-28 15:41   ` Marc Zyngier
2021-01-13 17:18     ` Auger Eric
2020-12-12 18:50 ` [PATCH 5/9] KVM: arm: move has_run_once after the map_resources Eric Auger
2021-01-12 14:55   ` Alexandru Elisei
2021-01-14 10:02     ` Auger Eric
2021-01-20 15:56       ` Alexandru Elisei
2021-03-12 17:27         ` Auger Eric
2020-12-12 18:50 ` [PATCH 6/9] docs: kvm: devices/arm-vgic-v3: enhance KVM_DEV_ARM_VGIC_CTRL_INIT doc Eric Auger
2021-01-12 15:39   ` Alexandru Elisei
2021-01-13 17:18     ` Auger Eric
2020-12-12 18:50 ` [PATCH 7/9] KVM: arm64: Simplify argument passing to vgic_uaccess_[read|write] Eric Auger
2021-01-12 16:04   ` Alexandru Elisei
2021-01-12 16:16     ` Alexandru Elisei
2021-01-13 17:18       ` Auger Eric
2020-12-12 18:50 ` [PATCH 8/9] KVM: arm64: vgic-v3: Expose GICR_TYPER.Last for userspace Eric Auger
2021-01-12 17:02   ` Alexandru Elisei
2021-01-14 10:16     ` Auger Eric
2021-01-20 16:13       ` Alexandru Elisei
2021-03-12 17:26         ` Auger Eric
2021-01-12 17:28   ` Alexandru Elisei [this message]
2021-01-12 17:48     ` Marc Zyngier
2020-12-12 18:50 ` [PATCH 9/9] KVM: selftests: aarch64/vgic-v3 init sequence tests Eric Auger

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