Message-ID: <5148de60-4a9d-67ef-ca64-5c6461034c0c@redhat.com>
Date:   Wed, 17 Nov 2021 14:06:59 +0100
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Subject: Re: [PATCH 2/2] KVM: SVM: Extend host physical APIC ID field to
 support more than 8-bit
Content-Language: en-US
To:     Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>,
        linux-kernel@vger.kernel.org, kvm@vger.kernel.org, x86@kernel.org
Cc:     joro@8bytes.org, tglx@linutronix.de, mingo@redhat.com,
        bp@alien8.de, peterz@infradead.org, hpa@zytor.com,
        thomas.lendacky@amd.com, jon.grimm@amd.com
References: <20211110101805.16343-1-suravee.suthikulpanit@amd.com>
 <20211110101805.16343-3-suravee.suthikulpanit@amd.com>
From:   Paolo Bonzini <pbonzini@redhat.com>
In-Reply-To: <20211110101805.16343-3-suravee.suthikulpanit@amd.com>
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On 11/10/21 11:18, Suravee Suthikulpanit wrote:
> +	if (level_type != 2 || !x2apic_mode) {
> +		avic_host_physical_id_mask = 0xffULL;
> +		goto out;
> +	}
> +
> +	core_mask_width = eax & 0xF;
> +
> +	max_phys_mask_width = get_count_order(apic_get_max_phys_apicid());
> +
> +	/*
> +	 * Sanity check to ensure core_mask_width for a processor does not
> +	 * exceed the calculated mask.
> +	 */
> +	if (WARN_ON(core_mask_width > max_phys_mask_width))
> +		return -EINVAL;

Can it just use apic_get_max_phys_apicid() in x2apic mode, and 0xff in 
!x2apic mode?  I'm not sure why you need to check CPUID[0xb,0x1].

Paolo