From: Ralf Baechle <ralf@linux-mips.org>
To: James Hogan <james.hogan@imgtec.com>
Cc: linux-mips@linux-mips.org, "Paolo Bonzini" <pbonzini@redhat.com>,
"Radim Krčmář" <rkrcmar@redhat.com>,
kvm@vger.kernel.org, stable@vger.kernel.org
Subject: Re: [PATCH] KVM: MIPS/Emulate: Fix preemption warning
Date: Wed, 15 Mar 2017 15:15:42 +0100 [thread overview]
Message-ID: <20170315141542.GF5512@linux-mips.org> (raw)
In-Reply-To: <20170314000515.26573-1-james.hogan@imgtec.com>
On Tue, Mar 14, 2017 at 12:05:15AM +0000, James Hogan wrote:
> Host kernels with preemption enabled will emit the following preemption
> warning when the guest FPU is used:
>
> BUG: using smp_processor_id() in preemptible [00000000] code: qemu-system-mip/1495
> caller is kvm_mips_emulate_CP0+0xa48/0xea0 [kvm]
> ...
> Call Trace:
> [<ffffffff81122d50>] show_stack+0x88/0xa8
> [<ffffffff814307ac>] dump_stack+0x9c/0xd0
> [<ffffffff81459f24>] check_preemption_disabled+0x124/0x130
> [<ffffffffc000e908>] kvm_mips_emulate_CP0+0xa48/0xea0 [kvm]
> [<ffffffffc000f9f0>] kvm_mips_emulate_inst+0x190/0x268 [kvm]
> [<ffffffffc0016220>] kvm_trap_emul_handle_cop_unusable+0x48/0x160 [kvm]
> [<ffffffffc000c120>] kvm_mips_handle_exit+0x520/0x7e0 [kvm]
>
> This is due to the use of current_cpu_data.fpu_id from a preemptible
> context to read the MIPS_FPIR_F64 bit. We don't currently support
> asymmetric FPU capabilities with KVM, so just use boot_cpu_data instead
> to silence the warning.
>
> Fixes: 6cdc65e31d4f ("MIPS: KVM: Emulate FPU bits in COP0 interface")
> Signed-off-by: James Hogan <james.hogan@imgtec.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: "Radim Krčmář" <rkrcmar@redhat.com>
> Cc: Ralf Baechle <ralf@linux-mips.org>
> Cc: linux-mips@linux-mips.org
> Cc: kvm@vger.kernel.org
> Cc: <stable@vger.kernel.org> # 4.1.x-
Acked-by: Ralf Baechle <ralf@linux-mips.org>
James, we've fixed too many of these warnings over the past years, we
should look for a solution to kill this whole class of bugs.
Ralf
prev parent reply other threads:[~2017-03-15 15:28 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-14 0:05 [PATCH] KVM: MIPS/Emulate: Fix preemption warning James Hogan
2017-03-14 0:05 ` James Hogan
2017-03-15 14:15 ` Ralf Baechle [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20170315141542.GF5512@linux-mips.org \
--to=ralf@linux-mips.org \
--cc=james.hogan@imgtec.com \
--cc=kvm@vger.kernel.org \
--cc=linux-mips@linux-mips.org \
--cc=pbonzini@redhat.com \
--cc=rkrcmar@redhat.com \
--cc=stable@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.