Messages in this thread | | | Date | Fri, 22 Feb 2008 13:48:30 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH] X86: don't print a warning when MTRR are blank and running in KVM |
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* Joerg Roedel <joerg.roedel@amd.com> wrote:
> > ok. Then i guess we should just leave the warning and the backtrace > > in place until they get a fix done? > > No. I don't agree. The MTRRs are set up by the BIOS because it knows > the hardware best (I know this is only true in theory). The OS should > basically trust the BIOS MTRR settings. If the OS can't trust the > BIOS, like on real hardware, the check and the warning is necessary. > If the OS can trust the BIOS, like running in a KVM or QEMU virtual > machine, it should just ignore the case where all MTRRs are blank.
well, i can agree with the warning being pointless on KVM paravirt, but it's not pointless in the Qemu context.
we fundamentall _dont_ trust the BIOS's MTRR settings, just check the very function that you modified: mtrr_trim_uncached_memory() - that function handles _exactly_ a case where a BIOS messes up MTRR's. This problem has caused real user-side breakage and just not emitting a warning because Qemu is lazy to emulate a proper PC is not a strong enough argument.
so i've applied the KVM bits but the warning stays for Qemu.
Ingo
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