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Groups > linux.kernel > #1356494
| From | Borislav Petkov <bp@alien8.de> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH] x86/FPU: Fix FPU handling on legacy FPU machines |
| Date | 2016-03-12 18:50 +0100 |
| Message-ID | <rbVPQ-1dq-9@gated-at.bofh.it> (permalink) |
| References | (5 earlier) <rbA8G-1R9-25@gated-at.bofh.it> <rbDpT-4rR-3@gated-at.bofh.it> <rbDpT-4rR-1@gated-at.bofh.it> <rbDJg-4zW-1@gated-at.bofh.it> <rbVwu-14n-11@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On Sat, Mar 12, 2016 at 09:21:16AM -0800, Andy Lutomirski wrote:
> For reference, what are the QEMU options and boot options you used to
> trigger this? I'm asking because I tested eagerfpu=on without fxsr a
> few weeks ago in QEMU, and I didn't trigger it. Maybe I needed to
> force KVM off or something.
$ qemu-system-i386
-enable-kvm
-gdb tcp::1234
-cpu 486
-m 2048
-hda /home/boris/kvm/debian/sid-i386.img
-boot menu=off,order=c
-localtime
-net nic,model=rtl8139,macaddr=12:35:12:34:56:78
-net user,hostfwd=tcp::1235-:22
-usbdevice tablet
-kernel /home/boris/kernel/linux-2.6/arch/x86/boot/bzImage
-append "root=/dev/sda1 resume=/dev/sdb1 debug ignore_loglevel log_buf_len=16M earlyprintk=ttyS0,115200 console=ttyS0,115200 console=tty0 "
-monitor pty
-soundhw hda
-serial file:/home/boris/kvm/test-i386-1235.log
-snapshot
-name "Debian i386:1235"
-smp 1
-virtfs local,path=/tmp,mount_tag=tmp,security_model=none
I basically tried to get it as close to 486er as possible. I had also
CONFIG_M486=y for the guest kernel.
> Off the top of my head, I'm guessing that when I wrote "x86/fpu: Fix
> FNSAVE usage in eagerfpu mode", I was inadvertently using a bastardize
> combination of FNSAVE and FXRSTOR-of-init-state, KVM let the FXRSTOR
> through despite not advertising it in CPUID, and it papered over the
> init issue because the wrong init state format was hidden by using the
> wrong instruction to load it.
Yeah, I think qemu looks at CPUID bits for some stuff but probably not
all. And I also think we should go and fix such issues there so that we
can have as accurate an emulation as possible.
> Sigh. Yet more reason for Intel to add chicken bits to *turn off* new
> features.
Amen to that.
--
Regards/Gruss,
Boris.
ECO tip #101: Trim your mails when you reply.
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Got FPU related warning on Intel Quark during boot Andy Shevchenko <andy.shevchenko@gmail.com> - 2016-03-10 11:50 +0100
Re: Got FPU related warning on Intel Quark during boot Ingo Molnar <mingo@kernel.org> - 2016-03-10 12:20 +0100
Re: Got FPU related warning on Intel Quark during boot Andy Shevchenko <andy.shevchenko@gmail.com> - 2016-03-10 13:50 +0100
Re: Got FPU related warning on Intel Quark during boot Borislav Petkov <bp@alien8.de> - 2016-03-10 14:00 +0100
Re: Got FPU related warning on Intel Quark during boot Andy Shevchenko <andy.shevchenko@gmail.com> - 2016-03-10 14:40 +0100
Re: Got FPU related warning on Intel Quark during boot Borislav Petkov <bp@alien8.de> - 2016-03-10 16:10 +0100
Re: Got FPU related warning on Intel Quark during boot Andy Shevchenko <andy.shevchenko@gmail.com> - 2016-03-10 16:30 +0100
Re: Got FPU related warning on Intel Quark during boot Bryan O'Donoghue <pure.logic@nexus-software.ie> - 2016-03-10 16:50 +0100
Re: Got FPU related warning on Intel Quark during boot Borislav Petkov <bp@alien8.de> - 2016-03-10 17:50 +0100
Re: Got FPU related warning on Intel Quark during boot Bryan O'Donoghue <pure.logic@nexus-software.ie> - 2016-03-10 18:20 +0100
Re: Got FPU related warning on Intel Quark during boot Borislav Petkov <bp@alien8.de> - 2016-03-10 20:10 +0100
Re: Got FPU related warning on Intel Quark during boot Andy Lutomirski <luto@amacapital.net> - 2016-03-11 02:40 +0100
Re: Got FPU related warning on Intel Quark during boot Bryan O'Donoghue <pure.logic@nexus-software.ie> - 2016-03-11 12:00 +0100
Re: Got FPU related warning on Intel Quark during boot Andy Lutomirski <luto@amacapital.net> - 2016-03-11 02:50 +0100
Re: Got FPU related warning on Intel Quark during boot Ingo Molnar <mingo@kernel.org> - 2016-03-11 10:10 +0100
Re: Got FPU related warning on Intel Quark during boot Borislav Petkov <bp@alien8.de> - 2016-03-11 10:50 +0100
Re: Got FPU related warning on Intel Quark during boot Bryan O'Donoghue <pure.logic@nexus-software.ie> - 2016-03-11 12:10 +0100
Re: Got FPU related warning on Intel Quark during boot Borislav Petkov <bp@alien8.de> - 2016-03-11 12:30 +0100
[PATCH] x86/FPU: Fix FPU handling on legacy FPU machines Borislav Petkov <bp@alien8.de> - 2016-03-11 12:40 +0100
Re: [PATCH] x86/FPU: Fix FPU handling on legacy FPU machines Linus Torvalds <torvalds@linux-foundation.org> - 2016-03-11 19:40 +0100
Re: [PATCH] x86/FPU: Fix FPU handling on legacy FPU machines Dave Hansen <dave.hansen@linux.intel.com> - 2016-03-11 23:10 +0100
Re: [PATCH] x86/FPU: Fix FPU handling on legacy FPU machines Borislav Petkov <bp@alien8.de> - 2016-03-11 23:30 +0100
Re: [PATCH] x86/FPU: Fix FPU handling on legacy FPU machines Andy Lutomirski <luto@amacapital.net> - 2016-03-12 18:30 +0100
Re: [PATCH] x86/FPU: Fix FPU handling on legacy FPU machines Borislav Petkov <bp@alien8.de> - 2016-03-12 18:50 +0100
Re: [PATCH] x86/FPU: Fix FPU handling on legacy FPU machines Borislav Petkov <bp@alien8.de> - 2016-03-11 23:10 +0100
Re: [PATCH] x86/FPU: Fix FPU handling on legacy FPU machines Bryan O'Donoghue <pure.logic@nexus-software.ie> - 2016-03-12 13:10 +0100
Re: [PATCH] x86/FPU: Fix FPU handling on legacy FPU machines Borislav Petkov <bp@alien8.de> - 2016-03-12 13:30 +0100
Re: [PATCH] x86/FPU: Fix FPU handling on legacy FPU machines Ingo Molnar <mingo@kernel.org> - 2016-03-12 16:20 +0100
Re: [PATCH] x86/FPU: Fix FPU handling on legacy FPU machines Ingo Molnar <mingo@kernel.org> - 2016-03-12 16:10 +0100
Re: [PATCH] x86/FPU: Fix FPU handling on legacy FPU machines Ingo Molnar <mingo@kernel.org> - 2016-03-12 16:20 +0100
[tip:x86/urgent] x86/fpu: Fix eager-FPU handling on legacy FPU machines tip-bot for Borislav Petkov <tipbot@zytor.com> - 2016-03-12 16:20 +0100
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