linux-kernel - Re: [PATCH 4.19 111/120] KVM: do not assume PTE is writable after follow

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Date:   Tue, 27 Jul 2021 11:33:18 +0300
From:   Ovidiu Panait <ovidiu.panait@...driver.com>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        Sudip Mukherjee <sudipm.mukherjee@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel <linux-kernel@...r.kernel.org>,
        Stable <stable@...r.kernel.org>,
        David Stevens <stevensd@...gle.com>, 3pvd@...gle.com,
        Jann Horn <jannh@...gle.com>, Jason Gunthorpe <jgg@...pe.ca>
Subject: Re: [PATCH 4.19 111/120] KVM: do not assume PTE is writable after
 follow_pfn

Hi,

On 7/27/21 1:02 AM, Paolo Bonzini wrote:

> [Please note: This e-mail is from an EXTERNAL e-mail address]
>
> On 26/07/21 23:17, Sudip Mukherjee wrote:
>> Hi Greg,
>>
>> On Mon, Jul 26, 2021 at 4:58 PM Greg Kroah-Hartman
>> <gregkh@...uxfoundation.org> wrote:
>>>
>>> From: Paolo Bonzini <pbonzini@...hat.com>
>>>
>>> commit bd2fae8da794b55bf2ac02632da3a151b10e664c upstream.
>>
>> The build of mips malta_kvm_defconfig fails with the error:
>> In file included from arch/mips/kvm/../../../virt/kvm/kvm_main.c:21:
>> arch/mips/kvm/../../../virt/kvm/kvm_main.c: In function 
>> 'hva_to_pfn_remapped':
>> ./include/linux/kvm_host.h:70:33: error: conversion from 'long long
>> unsigned int' to 'long unsigned int' changes value from
>> '9218868437227405314' to '2' [-Werror=overflow]
>>     70 | #define KVM_PFN_ERR_RO_FAULT    (KVM_PFN_ERR_MASK + 2)
>>        |                                 ^
>> arch/mips/kvm/../../../virt/kvm/kvm_main.c:1530:23: note: in expansion
>> of macro 'KVM_PFN_ERR_RO_FAULT'
>>   1530 |                 pfn = KVM_PFN_ERR_RO_FAULT;
>>
>> It built fine after reverting this patch.
>> gcc version 11.1.1 20210723
>
> I'll resend a version that works tomorrow (including the second patch
> too, which depends on this one for context).
>
The following upstream commit needed to be backported as well:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=a9545779ee9e9e103648f6f2552e73cfe808d0f4


I have sent v2 for this patchset.


Thanks!

Ovidiu


> Paolo
>