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From: Maxim Levitsky <mlevitsk@redhat.com>
To: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>,
	linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Cc: pbonzini@redhat.com, seanjc@google.com, joro@8bytes.org,
	jon.grimm@amd.com, wei.huang2@amd.com, terry.bowman@amd.com
Subject: Re: [RFCv2 PATCH 06/12] KVM: SVM: Do not update logical APIC ID table when in x2APIC mode
Date: Thu, 24 Mar 2022 13:37:55 +0200	[thread overview]
Message-ID: <8da749c7fec55633e4c65f38a00040afbb22f85a.camel@redhat.com> (raw)
In-Reply-To: <20220308163926.563994-7-suravee.suthikulpanit@amd.com>

On Tue, 2022-03-08 at 10:39 -0600, Suravee Suthikulpanit wrote:
> In X2APIC mode the Logical Destination Register is read-only,
> which provides a fixed mapping between the logical and physical
> APIC IDs. Therefore, there is no Logical APIC ID table in X2AVIC
> and the processor uses the X2APIC ID in the backing page to create
> a vCPU’s logical ID. Also, when x2AVIC is activated, a guest write
> to the x2APIC LDR register would result in #GP injection into
> the guest by the hardware.
> 
> Therefore, add logic to check x2APIC mode before updating logical
> APIC ID table.
> 
> Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
> ---
>  arch/x86/kvm/svm/avic.c | 11 ++++++++++-
>  1 file changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
> index 5329b93dc4cd..4d7a8743196e 100644
> --- a/arch/x86/kvm/svm/avic.c
> +++ b/arch/x86/kvm/svm/avic.c
> @@ -406,6 +406,10 @@ static int avic_ldr_write(struct kvm_vcpu *vcpu, u8 g_physical_id, u32 ldr)
>  	bool flat;
>  	u32 *entry, new_entry;
>  
> +	/* Note: x2AVIC does not use logical APIC ID table */
> +	if (apic_x2apic_mode(vcpu->arch.apic))
> +		return 0;
> +
>  	flat = kvm_lapic_get_reg(vcpu->arch.apic, APIC_DFR) == APIC_DFR_FLAT;
>  	entry = avic_get_logical_id_entry(vcpu, ldr, flat);
>  	if (!entry)
> @@ -424,8 +428,13 @@ static void avic_invalidate_logical_id_entry(struct kvm_vcpu *vcpu)
>  {
>  	struct vcpu_svm *svm = to_svm(vcpu);
>  	bool flat = svm->dfr_reg == APIC_DFR_FLAT;
> -	u32 *entry = avic_get_logical_id_entry(vcpu, svm->ldr_reg, flat);
> +	u32 *entry;
> +
> +	/* Note: x2AVIC does not use logical APIC ID table */
> +	if (apic_x2apic_mode(vcpu->arch.apic))
> +		return;
>  
> +	entry = avic_get_logical_id_entry(vcpu, svm->ldr_reg, flat);
>  	if (entry)
>  		clear_bit(AVIC_LOGICAL_ID_ENTRY_VALID_BIT, (unsigned long *)entry);
>  }

Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>

Best regards,
	Maxim Levitsky


  reply	other threads:[~2022-03-24 11:38 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-03-08 16:39 [RFCv2 PATCH 00/12] Introducing AMD x2APIC Virtualization (x2AVIC) support Suravee Suthikulpanit
2022-03-08 16:39 ` [RFCv2 PATCH 01/12] x86/cpufeatures: Introduce x2AVIC CPUID bit Suravee Suthikulpanit
2022-03-08 16:39 ` [RFCv2 PATCH 02/12] KVM: x86: lapic: Rename [GET/SET]_APIC_DEST_FIELD to [GET/SET]_XAPIC_DEST_FIELD Suravee Suthikulpanit
2022-03-24 10:30   ` Maxim Levitsky
2022-03-08 16:39 ` [RFCv2 PATCH 03/12] KVM: SVM: Detect X2APIC virtualization (x2AVIC) support Suravee Suthikulpanit
2022-03-24 10:53   ` Maxim Levitsky
2022-03-08 16:39 ` [RFCv2 PATCH 04/12] KVM: SVM: Update max number of vCPUs supported for x2AVIC mode Suravee Suthikulpanit
2022-03-24 11:13   ` Maxim Levitsky
2022-03-08 16:39 ` [RFCv2 PATCH 05/12] KVM: SVM: Update avic_kick_target_vcpus to support 32-bit APIC ID Suravee Suthikulpanit
2022-03-24 11:36   ` Maxim Levitsky
2022-03-08 16:39 ` [RFCv2 PATCH 06/12] KVM: SVM: Do not update logical APIC ID table when in x2APIC mode Suravee Suthikulpanit
2022-03-24 11:37   ` Maxim Levitsky [this message]
2022-03-08 16:39 ` [RFCv2 PATCH 07/12] KVM: SVM: Introduce helper function kvm_get_apic_id Suravee Suthikulpanit
2022-03-24 14:14   ` Maxim Levitsky
2022-04-05  3:58     ` Suravee Suthikulpanit
2022-04-05  9:36       ` Suravee Suthikulpanit
2022-03-08 16:39 ` [RFCv2 PATCH 08/12] KVM: SVM: Adding support for configuring x2APIC MSRs interception Suravee Suthikulpanit
2022-03-24 15:19   ` Maxim Levitsky
2022-04-05  1:45     ` Suravee Suthikulpanit
2022-03-08 16:39 ` [RFCv2 PATCH 09/12] KVM: SVM: Refresh AVIC settings when changing APIC mode Suravee Suthikulpanit
2022-03-24 15:35   ` Maxim Levitsky
2022-03-31  4:04     ` Suravee Suthikulpanit
2022-03-08 16:39 ` [RFCv2 PATCH 10/12] KVM: SVM: Introduce helper functions to (de)activate AVIC and x2AVIC Suravee Suthikulpanit
2022-03-24 15:40   ` Maxim Levitsky
2022-03-08 16:39 ` [RFCv2 PATCH 11/12] KVM: SVM: Do not throw warning when calling avic_vcpu_load on a running vcpu Suravee Suthikulpanit
2022-03-24 15:42   ` Maxim Levitsky
2022-03-08 16:39 ` [RFCv2 PATCH 12/12] KVM: SVM: Do not inhibit APICv when x2APIC is present Suravee Suthikulpanit

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