linux-kernel - Re: [PATCH v1 2/2] perf/x86/kvm: Avoid unnecessary work in guest filtering

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date:   Sat, 6 Oct 2018 16:40:53 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Andi Kleen <andi@...stfloor.org>
cc:     peterz@...radead.org, x86@...nel.org, linux-kernel@...r.kernel.org,
        eranian@...gle.com, kan.liang@...el.com, isaku.yamahata@...el.com,
        kvm@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH v1 2/2] perf/x86/kvm: Avoid unnecessary work in guest
 filtering

On Fri, 5 Oct 2018, Andi Kleen wrote:
> Some time ago KVM added a workaround for PEBS events leaking
> into guests. This uses the KVM entry/exit list to add an extra
> disable of the PEBS_ENABLE MSR.
> 
> Intel also added a fix for this issue to microcode updates on
> Haswell/Broadwell/Skylake.
> 
> It turns out using the MSR entry/exit list makes VM exits
> significantly slower. The list is only needed for disabling
> PEBS, because the GLOBAL_CTRL change gets optimized by
> KVM into changing the VMCS.
> 
> This patch checks for the microcode updates that have the microcode

# grep "This patch" Documentation/process

> fix for leaking PEBS, and disables the extra entry/exit list
> entry for PEBS_ENABLE. In addition we always clear the
> GLOBAL_CTRL for the PEBS counter while running in the guest,
> which is enough to make them never fire at the wrong
> side of the host/guest transition.
>  
> +#define IUCODE(model, step, rev) \
> +	{ X86_VENDOR_INTEL, 6, model, step, rev, 0, 0 }

So we are going to have this kind of defines on every usage site. Please
put these macros into the corresponding header file.

Also this wants to be named INTEL_MIN_UCODE() so it's clear what this is
about.

Thanks,

	tglx