From: Peter Xu <peterx@redhat.com>
To: Sean Christopherson <seanjc@google.com>
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
Paolo Bonzini <pbonzini@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
David Hildenbrand <david@redhat.com>,
"Dr . David Alan Gilbert" <dgilbert@redhat.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Linux MM Mailing List <linux-mm@kvack.org>
Subject: Re: [PATCH 3/4] kvm: Add new pfn error KVM_PFN_ERR_INTR
Date: Thu, 23 Jun 2022 15:32:39 -0400 [thread overview]
Message-ID: <YrS/13dBmSIpvd3C@xz-m1.local> (raw)
In-Reply-To: <YrR5U1mHP9fYQ1k9@google.com>
On Thu, Jun 23, 2022 at 02:31:47PM +0000, Sean Christopherson wrote:
> On Wed, Jun 22, 2022, Peter Xu wrote:
> > Add one new PFN error type to show when we cannot finish fetching the PFN
> > due to interruptions. For example, by receiving a generic signal.
> >
> > This prepares KVM to be able to respond to SIGUSR1 (for QEMU that's the
> > SIGIPI) even during e.g. handling an userfaultfd page fault.
> >
> > Signed-off-by: Peter Xu <peterx@redhat.com>
> > ---
> > include/linux/kvm_host.h | 11 +++++++++++
> > 1 file changed, 11 insertions(+)
> >
> > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> > index b646b6fcaec6..4f84a442f67f 100644
> > --- a/include/linux/kvm_host.h
> > +++ b/include/linux/kvm_host.h
> > @@ -96,6 +96,7 @@
> > #define KVM_PFN_ERR_FAULT (KVM_PFN_ERR_MASK)
> > #define KVM_PFN_ERR_HWPOISON (KVM_PFN_ERR_MASK + 1)
> > #define KVM_PFN_ERR_RO_FAULT (KVM_PFN_ERR_MASK + 2)
> > +#define KVM_PFN_ERR_INTR (KVM_PFN_ERR_MASK + 3)
> >
> > /*
> > * error pfns indicate that the gfn is in slot but faild to
> > @@ -106,6 +107,16 @@ static inline bool is_error_pfn(kvm_pfn_t pfn)
> > return !!(pfn & KVM_PFN_ERR_MASK);
> > }
> >
> > +/*
> > + * When KVM_PFN_ERR_INTR is returned, it means we're interrupted during
> > + * fetching the PFN (e.g. a signal might have arrived), so we may want to
> > + * retry at some later point and kick the userspace to handle the signal.
> > + */
> > +static inline bool is_intr_pfn(kvm_pfn_t pfn)
> > +{
> > + return pfn == KVM_PFN_ERR_INTR;
>
> What about is_sigpending_pfn() and KVM_PFN_ERR_SIGPENDING? "intr" is too close to
> a real thing KVM will encounter, and I think knowing that KVM is effectively
> responding to a pending signal is the most important detail for KVM developers
> encountering this code for this first time. E.g. from KVM_PFN_ERR_INTR alone, one
> might think that any interrupt during GUP will trigger this.
Sounds good; INTR could be too general for KVM indeed. Thanks,
--
Peter Xu
next prev parent reply other threads:[~2022-06-23 19:42 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-22 21:36 [PATCH 0/4] kvm/mm: Allow GUP to respond to non fatal signals Peter Xu
2022-06-22 21:36 ` [PATCH 1/4] mm/gup: Add FOLL_INTERRUPTIBLE Peter Xu
2022-06-25 0:35 ` Jason Gunthorpe
2022-06-25 1:23 ` Peter Xu
2022-06-25 23:59 ` Jason Gunthorpe
2022-06-27 15:29 ` Peter Xu
2022-06-28 2:07 ` John Hubbard
2022-06-28 19:31 ` Peter Xu
2022-06-28 21:40 ` John Hubbard
2022-06-28 22:33 ` Peter Xu
2022-06-29 0:31 ` John Hubbard
2022-06-29 15:47 ` Peter Xu
2022-06-30 1:53 ` John Hubbard
2022-06-30 13:49 ` Peter Xu
2022-06-30 19:01 ` John Hubbard
2022-06-30 21:27 ` Peter Xu
2022-07-04 22:48 ` Matthew Wilcox
2022-07-07 15:06 ` Peter Xu
2022-06-22 21:36 ` [PATCH 2/4] kvm: Merge "atomic" and "write" in __gfn_to_pfn_memslot() Peter Xu
2022-06-23 14:49 ` Sean Christopherson
2022-06-23 19:46 ` Peter Xu
2022-06-23 20:29 ` Sean Christopherson
2022-06-23 21:29 ` Peter Xu
2022-06-23 21:52 ` Sean Christopherson
2022-06-27 19:12 ` John Hubbard
2022-06-28 2:17 ` John Hubbard
2022-06-28 19:46 ` Peter Xu
2022-06-28 21:52 ` John Hubbard
2022-06-28 22:50 ` Peter Xu
2022-06-28 22:55 ` John Hubbard
2022-06-28 23:02 ` Peter Xu
2022-06-22 21:36 ` [PATCH 3/4] kvm: Add new pfn error KVM_PFN_ERR_INTR Peter Xu
2022-06-23 14:31 ` Sean Christopherson
2022-06-23 19:32 ` Peter Xu [this message]
2022-06-22 21:36 ` [PATCH 4/4] kvm/x86: Allow to respond to generic signals during slow page faults Peter Xu
2022-06-23 14:46 ` Sean Christopherson
2022-06-23 19:31 ` Peter Xu
2022-06-23 20:07 ` Sean Christopherson
2022-06-23 20:18 ` Peter Xu
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