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fcb732d8f8
There are circumstances whem kvm_xen_update_runstate_guest() should not
sleep because it ends up being called from __schedule() when the vCPU
is preempted:
[ 222.830825] kvm_xen_update_runstate_guest+0x24/0x100
[ 222.830878] kvm_arch_vcpu_put+0x14c/0x200
[ 222.830920] kvm_sched_out+0x30/0x40
[ 222.830960] __schedule+0x55c/0x9f0
To handle this, make it use the same trick as __kvm_xen_has_interrupt(),
of using the hva from the gfn_to_hva_cache directly. Then it can use
pagefault_disable() around the accesses and just bail out if the page
is absent (which is unlikely).
I almost switched to using a gfn_to_pfn_cache here and bailing out if
kvm_map_gfn() fails, like kvm_steal_time_set_preempted() does — but on
closer inspection it looks like kvm_map_gfn() will *always* fail in
atomic context for a page in IOMEM, which means it will silently fail
to make the update every single time for such guests, AFAICT. So I
didn't do it that way after all. And will probably fix that one too.
Cc: stable@vger.kernel.org
Fixes: 30b5c851af ("KVM: x86/xen: Add support for vCPU runstate information")
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Message-Id: <b17a93e5ff4561e57b1238e3e7ccd0b613eb827e.camel@infradead.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.