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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox