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Message-ID: <ZLsHq69sMG7pmRiz@google.com>
Date: Fri, 21 Jul 2023 15:33:15 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Isaku Yamahata <isaku.yamahata@...il.com>
Cc: Yuan Yao <yuan.yao@...ux.intel.com>,
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,
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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>,
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Wang <wei.w.wang@...el.com>,
Liam Merwick <liam.merwick@...cle.com>,
"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: Re: [RFC PATCH v11 12/29] KVM: Add KVM_CREATE_GUEST_MEMFD ioctl() for
guest-specific backing memory
On Fri, Jul 21, 2023, Isaku Yamahata wrote:
> On Fri, Jul 21, 2023 at 02:13:14PM +0800,
> Yuan Yao <yuan.yao@...ux.intel.com> wrote:
> > > +static int kvm_gmem_error_page(struct address_space *mapping, struct page *page)
> > > +{
> > > + struct list_head *gmem_list = &mapping->private_list;
> > > + struct kvm_memory_slot *slot;
> > > + struct kvm_gmem *gmem;
> > > + unsigned long index;
> > > + pgoff_t start, end;
> > > + gfn_t gfn;
> > > +
> > > + filemap_invalidate_lock_shared(mapping);
> > > +
> > > + start = page->index;
> > > + end = start + thp_nr_pages(page);
> > > +
> > > + list_for_each_entry(gmem, gmem_list, entry) {
> > > + xa_for_each_range(&gmem->bindings, index, slot, start, end - 1) {
> > > + for (gfn = start; gfn < end; gfn++) {
> >
> > Why the start end range used as gfn here ?
Math is hard? I almost always mess up these types of things, and then catch my
bugs via tests. But I don't have tests for this particular flow... Which
reminds me, we need tests for this :-) Hopefully error injection provides most
of what we need?
> > the page->index is offset of inode's page cache mapping and
> > gmem address space, IIUC, gfn calculation should follow same
> > way as kvm_gmem_invalidate_begin().
>
> Also instead of sending signal multiple times, we can utilize lsb argument.
As Vishal pointed out, this code shouldn't be sending signals in the first place.
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