linux-kernel - Re: [PATCH v2] x86/xen: Add support for HVMOP_set_evtchn_upcall

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Date:   Wed, 27 Jul 2022 15:42:46 +0000
From:   Jane Malalane <Jane.Malalane@...rix.com>
To:     Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        LKML <linux-kernel@...r.kernel.org>
CC:     Juergen Gross <jgross@...e.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Stefano Stabellini <sstabellini@...nel.org>,
        Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>,
        Maximilian Heyne <mheyne@...zon.de>,
        Jan Beulich <jbeulich@...e.com>,
        Colin Ian King <colin.king@...el.com>,
        "xen-devel@...ts.xenproject.org" <xen-devel@...ts.xenproject.org>
Subject: Re: [PATCH v2] x86/xen: Add support for
 HVMOP_set_evtchn_upcall_vector

On 27/07/2022 00:31, Boris Ostrovsky wrote:
> [CAUTION - EXTERNAL EMAIL] DO NOT reply, click links, or open 
> attachments unless you have verified the sender and know the content is 
> safe.
> 
> On 7/26/22 8:56 AM, Jane Malalane wrote:
>> +/* Setup per-vCPU vector-type callbacks and trick toolstack to think
>> + * we are enlightened. If this setup is unavailable, fallback to the
>> + * global vector-type callback. */
> 
> 
> Comment style.
> 
> 
>> +static __init void xen_init_setup_upcall_vector(void)
>> +{
>> +    unsigned int cpu = 0;
> 
> 
> Unnecessary variable.
> 
> 
>> +
>> +    if (!xen_have_vector_callback)
>> +        return;
>> +
>> +    if ((cpuid_eax(xen_cpuid_base() + 4) & 
>> XEN_HVM_CPUID_UPCALL_VECTOR) &&
>> +        !xen_set_upcall_vector(cpu) && !xen_set_callback_via(1))
>> +        xen_percpu_upcall = true;
>> +    else if (xen_feature(XENFEAT_hvm_callback_vector))
>> +        xen_setup_callback_vector();
>> +    else
>> +        xen_have_vector_callback = false;
>> +}
>> +
>> +int xen_set_upcall_vector(unsigned int cpu)
>> +{
>> +    int rc;
>> +    xen_hvm_evtchn_upcall_vector_t op = {
>> +        .vector = HYPERVISOR_CALLBACK_VECTOR,
>> +        .vcpu = per_cpu(xen_vcpu_id, cpu),
>> +    };
>> +
>> +    rc = HYPERVISOR_hvm_op(HVMOP_set_evtchn_upcall_vector, &op);
>> +    if (rc)
>> +        return rc;
>> +
>> +    if (!cpu)
> 
> 
> A comment (e.g. "Let toolstack know that we are enlightened." or 
> something along these lines) would be useful here.
>Thanks, will include all these changes in a v3.

Jane.