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

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Message-ID: <8cf86f5f-480a-7093-e890-467f290b0ed3@redhat.com>
Date:   Tue, 27 Jul 2021 00:02:44 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     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>,
        Ovidiu Panait <ovidiu.panait@...driver.com>
Subject: Re: [PATCH 4.19 111/120] KVM: do not assume PTE is writable after
 follow_pfn

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).

Paolo