linux-kernel - Re: [PATCH v1 2/8] x86/xen: simplify xen_oldmem_pfn_is

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Message-ID: <e6ace8c8-8a2d-9bf7-e65b-91d0037c4d08@redhat.com>
Date:   Wed, 29 Sep 2021 17:07:10 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        linux-kernel@...r.kernel.org
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, Juergen Gross <jgross@...e.com>,
        Stefano Stabellini <sstabellini@...nel.org>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Dave Young <dyoung@...hat.com>, Baoquan He <bhe@...hat.com>,
        Vivek Goyal <vgoyal@...hat.com>,
        Michal Hocko <mhocko@...e.com>,
        Oscar Salvador <osalvador@...e.de>,
        Mike Rapoport <rppt@...nel.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>, x86@...nel.org,
        xen-devel@...ts.xenproject.org,
        virtualization@...ts.linux-foundation.org,
        kexec@...ts.infradead.org, linux-fsdevel@...r.kernel.org,
        linux-mm@...ck.org
Subject: Re: [PATCH v1 2/8] x86/xen: simplify xen_oldmem_pfn_is_ram()

On 29.09.21 16:22, Boris Ostrovsky wrote:
> 
> On 9/29/21 5:03 AM, David Hildenbrand wrote:
>> On 29.09.21 10:45, David Hildenbrand wrote:
>>>>
>>> Can we go one step further and do
>>>
>>>
>>> @@ -20,24 +20,11 @@ static int xen_oldmem_pfn_is_ram(unsigned long pfn)
>>>            struct xen_hvm_get_mem_type a = {
>>>                    .domid = DOMID_SELF,
>>>                    .pfn = pfn,
>>> +               .mem_type = HVMMEM_ram_rw,
>>>            };
>>> -       int ram;
>>>     -       if (HYPERVISOR_hvm_op(HVMOP_get_mem_type, &a))
>>> -               return -ENXIO;
>>> -
>>> -       switch (a.mem_type) {
>>> -       case HVMMEM_mmio_dm:
>>> -               ram = 0;
>>> -               break;
>>> -       case HVMMEM_ram_rw:
>>> -       case HVMMEM_ram_ro:
>>> -       default:
>>> -               ram = 1;
>>> -               break;
>>> -       }
>>> -
>>> -       return ram;
>>> +       HYPERVISOR_hvm_op(HVMOP_get_mem_type, &a);
>>> +       return a.mem_type != HVMMEM_mmio_dm;
> 
> 
> I was actually thinking of asking you to add another patch with pr_warn_once() here (and print error code as well). This call failing is indication of something going quite wrong and it would be good to know about this.

Will include a patch in v2, thanks!


-- 
Thanks,

David / dhildenb