linux-kernel - Re: [RFC PATCH v11 07/29] KVM: Add KVM_EXIT_MEMORY

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Date:   Wed, 19 Jul 2023 07:16:54 -0700
From:   Sean Christopherson <seanjc@...gle.com>
To:     Yuan Yao <yuan.yao@...ux.intel.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>, Marc Zyngier <maz@...nel.org>,
        Oliver Upton <oliver.upton@...ux.dev>,
        Huacai Chen <chenhuacai@...nel.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Anup Patel <anup@...infault.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Paul Moore <paul@...l-moore.com>,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>, kvm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev,
        linux-mips@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        kvm-riscv@...ts.infradead.org, linux-riscv@...ts.infradead.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Chao Peng <chao.p.peng@...ux.intel.com>,
        Fuad Tabba <tabba@...gle.com>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        Yu Zhang <yu.c.zhang@...ux.intel.com>,
        Vishal Annapurve <vannapurve@...gle.com>,
        Ackerley Tng <ackerleytng@...gle.com>,
        Maciej Szmigiero <mail@...iej.szmigiero.name>,
        Vlastimil Babka <vbabka@...e.cz>,
        David Hildenbrand <david@...hat.com>,
        Quentin Perret <qperret@...gle.com>,
        Michael Roth <michael.roth@....com>,
        Wang <wei.w.wang@...el.com>,
        Liam Merwick <liam.merwick@...cle.com>,
        Isaku Yamahata <isaku.yamahata@...il.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: Re: [RFC PATCH v11 07/29] KVM: Add KVM_EXIT_MEMORY_FAULT exit

On Wed, Jul 19, 2023, Yuan Yao wrote:
> On Tue, Jul 18, 2023 at 04:44:50PM -0700, Sean Christopherson wrote:
> > From: Chao Peng <chao.p.peng@...ux.intel.com>
> >
> > This new KVM exit allows userspace to handle memory-related errors. It
> > indicates an error happens in KVM at guest memory range [gpa, gpa+size).
> > The flags includes additional information for userspace to handle the
> > error. Currently bit 0 is defined as 'private memory' where '1'
> > indicates error happens due to private memory access and '0' indicates
> > error happens due to shared memory access.
> 
> Now it's bit 3:

Yeah, I need to update (or write) a lot of changelogs.

> #define KVM_MEMORY_EXIT_FLAG_PRIVATE (1ULL << 3)
> 
> I remember some other attributes were introduced in v10 yet:
> 
> #define KVM_MEMORY_ATTRIBUTE_READ              (1ULL << 0)
> #define KVM_MEMORY_ATTRIBUTE_WRITE             (1ULL << 1)
> #define KVM_MEMORY_ATTRIBUTE_EXECUTE           (1ULL << 2)
> #define KVM_MEMORY_ATTRIBUTE_PRIVATE           (1ULL << 3)
> 
> So KVM_MEMORY_EXIT_FLAG_PRIVATE changed to bit 3 due to above things,
> or other reason ? (Sorry I didn't follow v10 too much before).

Yep, I want to reserve space for the RWX bits.