linux-kernel - Re: [PATCH 25/34] KVM: selftests: Add helpers to convert guest memory b/w private and shared

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Date:   Mon, 6 Nov 2023 16:24:42 +0000
From:   Fuad Tabba <tabba@...gle.com>
To:     Sean Christopherson <seanjc@...gle.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>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Christian Brauner <brauner@...nel.org>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>, 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-kernel@...r.kernel.org, Xiaoyao Li <xiaoyao.li@...el.com>,
        Xu Yilun <yilun.xu@...el.com>,
        Chao Peng <chao.p.peng@...ux.intel.com>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        Anish Moorthy <amoorthy@...gle.com>,
        David Matlack <dmatlack@...gle.com>,
        Yu Zhang <yu.c.zhang@...ux.intel.com>,
        Isaku Yamahata <isaku.yamahata@...el.com>,
        Mickaël Salaün <mic@...ikod.net>,
        Vlastimil Babka <vbabka@...e.cz>,
        Vishal Annapurve <vannapurve@...gle.com>,
        Ackerley Tng <ackerleytng@...gle.com>,
        Maciej Szmigiero <mail@...iej.szmigiero.name>,
        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: [PATCH 25/34] KVM: selftests: Add helpers to convert guest memory
 b/w private and shared

On Mon, Nov 6, 2023 at 4:13 PM Sean Christopherson <seanjc@...gle.com> wrote:
>
> On Mon, Nov 06, 2023, Fuad Tabba wrote:
> > On Sun, Nov 5, 2023 at 4:34 PM Paolo Bonzini <pbonzini@...hat.com> wrote:
> > > +void vm_guest_mem_fallocate(struct kvm_vm *vm, uint64_t base, uint64_t size,
> > > +                           bool punch_hole)
> > > +{
> > > +       const int mode = FALLOC_FL_KEEP_SIZE | (punch_hole ? FALLOC_FL_PUNCH_HOLE : 0);
> > > +       struct userspace_mem_region *region;
> > > +       uint64_t end = base + size;
> > > +       uint64_t gpa, len;
> > > +       off_t fd_offset;
> > > +       int ret;
> > > +
> > > +       for (gpa = base; gpa < end; gpa += len) {
> > > +               uint64_t offset;
> > > +
> > > +               region = userspace_mem_region_find(vm, gpa, gpa);
> > > +               TEST_ASSERT(region && region->region.flags & KVM_MEM_GUEST_MEMFD,
> > > +                           "Private memory region not found for GPA 0x%lx", gpa);
> > > +
> > > +               offset = (gpa - region->region.guest_phys_addr);
> >
> > nit: why the parentheses?
>
> I simply forgot to remove them when I changed the function to support spanning
> multiple memslots, i.e. when the code went from this
>
>         fd_offset = region->region.gmem_offset +
>                     (gpa - region->region.guest_phys_addr);
>
> to what you see above.

I wasn't actually expecting an answer, but I literally _did_ ask for it :)

Thanks,
/fuad