linux-kernel - Re: [PATCH v3 05/12] x86/xen: set MTRR state when running as Xen PV initial domain

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Message-ID: <432bb9b3-959e-1074-c0e6-a65ac46e489e@oracle.com>
Date:   Mon, 27 Feb 2023 08:52:05 -0500
From:   Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:     Juergen Gross <jgross@...e.com>, linux-kernel@...r.kernel.org,
        x86@...nel.org
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>, xen-devel@...ts.xenproject.org
Subject: Re: [PATCH v3 05/12] x86/xen: set MTRR state when running as Xen PV
 initial domain



On 2/27/23 2:12 AM, Juergen Gross wrote:
> On 24.02.23 22:00, Boris Ostrovsky wrote:
>>
>> On 2/23/23 4:32 AM, Juergen Gross wrote:
>>> +
>>> +    for (reg = 0; reg < MTRR_MAX_VAR_RANGES; reg++) {
>>> +        op.u.read_memtype.reg = reg;
>>> +        if (HYPERVISOR_platform_op(&op))
>>> +            break;
>>
>>
>> If we fail on the first iteration, do we still want to mark MTRRs are enabled/set in mtrr_overwrite_state()?
> 
> Hmm, good idea.
> 
> I think we should just drop the call of mtrr_overwrite_state() in this
> case.


TBH I am not sure what the right way is to handle errors here. What if the hypercall fails on second iteration?


-boris