From: Josh Poimboeuf <jpoimboe@kernel.org>
To: Borislav Petkov <bp@alien8.de>
Cc: Kim Phillips <kim.phillips@amd.com>,
x86@kernel.org, Boris Ostrovsky <boris.ostrovsky@oracle.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
"H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
Joao Martins <joao.m.martins@oracle.com>,
Jonathan Corbet <corbet@lwn.net>,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Sean Christopherson <seanjc@google.com>,
Thomas Gleixner <tglx@linutronix.de>,
David Woodhouse <dwmw@amazon.co.uk>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Juergen Gross <jgross@suse.com>,
Peter Zijlstra <peterz@infradead.org>,
Tony Luck <tony.luck@intel.com>,
Tom Lendacky <thomas.lendacky@amd.com>,
Alexey Kardashevskiy <aik@amd.com>,
kvm@vger.kernel.org, linux-doc@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v9 7/8] x86/cpu: Support AMD Automatic IBRS
Date: Fri, 24 Feb 2023 16:09:31 -0800 [thread overview]
Message-ID: <20230225000931.wrednfun4jifkqau@treble> (raw)
In-Reply-To: <Y/k/ZXUXOFiBhOiI@zn.tnic>
On Fri, Feb 24, 2023 at 11:51:17PM +0100, Borislav Petkov wrote:
> On Fri, Feb 24, 2023 at 10:08:32PM +0100, Borislav Petkov wrote:
> > On Fri, Feb 24, 2023 at 10:52:57AM -0800, Josh Poimboeuf wrote:
> > > Doesn't this only enable it on the boot CPU?
> >
> > Whoops, you might be right.
>
> Actually, we stick that MSR - EFER - into the trampoline header and then
> each AP gets it written to in arch/x86/realmode/rm/trampoline_64.S
>
> But this is only from code staring - I'll confirm this tomorrow.
Ah, I had to stare it that for a bit to figure out how it works.
setup_real_mode() reads MSR_EFER from the boot CPU and stores it in
trampoline_header->efer. Then the other CPUs read that stored value in
startup_32() and write it into their MSR.
> And if so, we should at least put comments in that trampoline code so
> that people do not remove the MSR writes.
>
> Or, actually, we should simply write it again because it is the init
> path and not really a hot path but it should damn well make sure that
> that bit gets set.
Yeah, I think that would be good. Otherwise it's rather magical. That
EFER MSR is a surprising place to put that bit.
--
Josh
next prev parent reply other threads:[~2023-02-25 0:09 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-24 16:33 [PATCH v9 0/8] x86/cpu, kvm: Support AMD Automatic IBRS Kim Phillips
2023-01-24 16:33 ` [PATCH v9 1/8] x86/cpu, kvm: Add support for CPUID_80000021_EAX Kim Phillips
2023-01-26 10:12 ` [tip: x86/cpu] " tip-bot2 for Kim Phillips
2023-01-24 16:33 ` [PATCH v9 2/8] KVM: x86: Move open-coded cpuid leaf 0x80000021 EAX bit propagation code Kim Phillips
2023-01-26 10:12 ` [tip: x86/cpu] KVM: x86: Move open-coded CPUID " tip-bot2 for Kim Phillips
2023-01-24 16:33 ` [PATCH v9 3/8] x86/cpu, kvm: Add the NO_NESTED_DATA_BP feature Kim Phillips
2023-01-26 10:12 ` [tip: x86/cpu] " tip-bot2 for Kim Phillips
2023-01-24 16:33 ` [PATCH v9 4/8] x86/cpu, kvm: Move X86_FEATURE_LFENCE_RDTSC to its native leaf Kim Phillips
2023-01-24 21:32 ` Sean Christopherson
2023-01-25 12:09 ` Borislav Petkov
2023-01-26 10:12 ` [tip: x86/cpu] " tip-bot2 for Kim Phillips
2023-01-24 16:33 ` [PATCH v9 5/8] x86/cpu, kvm: Add the Null Selector Clears Base feature Kim Phillips
2023-01-26 10:12 ` [tip: x86/cpu] " tip-bot2 for Kim Phillips
2023-01-24 16:33 ` [PATCH v9 6/8] x86/cpu, kvm: Add the SMM_CTL MSR not present feature Kim Phillips
2023-01-26 10:12 ` [tip: x86/cpu] " tip-bot2 for Kim Phillips
2023-01-24 16:33 ` [PATCH v9 7/8] x86/cpu: Support AMD Automatic IBRS Kim Phillips
2023-01-26 10:12 ` [tip: x86/cpu] " tip-bot2 for Kim Phillips
2023-02-24 18:52 ` [PATCH v9 7/8] " Josh Poimboeuf
2023-02-24 21:08 ` Borislav Petkov
2023-02-24 21:35 ` Josh Poimboeuf
2023-02-24 21:59 ` Borislav Petkov
2023-02-24 22:03 ` Luck, Tony
2023-02-24 22:12 ` Borislav Petkov
2023-02-24 23:30 ` pawan.kumar.gupta
2023-03-10 10:23 ` [tip: x86/misc] MAINTAINERS: Add x86 hardware vulnerabilities section tip-bot2 for Josh Poimboeuf
2023-02-24 22:51 ` [PATCH v9 7/8] x86/cpu: Support AMD Automatic IBRS Borislav Petkov
2023-02-24 23:23 ` Borislav Petkov
2023-02-25 0:09 ` Josh Poimboeuf [this message]
2023-02-25 0:20 ` [PATCH] x86/CPU/AMD: Make sure EFER[AIBRSE] is set Borislav Petkov
2023-02-25 0:52 ` Pawan Gupta
2023-02-25 1:32 ` Josh Poimboeuf
2023-02-25 12:21 ` Borislav Petkov
2023-02-25 17:28 ` Josh Poimboeuf
2023-02-25 22:56 ` Borislav Petkov
2023-02-25 23:43 ` Josh Poimboeuf
2023-02-26 11:18 ` Borislav Petkov
2023-02-26 17:27 ` Josh Poimboeuf
2023-02-26 18:44 ` Borislav Petkov
2023-02-27 15:25 ` Dave Hansen
2023-02-27 15:40 ` Borislav Petkov
2023-02-27 16:39 ` Dave Hansen
2023-03-10 16:22 ` [PATCH -v2] " Borislav Petkov
2023-03-13 15:42 ` Dave Hansen
2023-03-16 11:04 ` [tip: x86/cpu] " tip-bot2 for Borislav Petkov (AMD)
2023-01-24 16:33 ` [PATCH v9 8/8] KVM: x86: Propagate the AMD Automatic IBRS feature to the guest Kim Phillips
2023-01-26 10:12 ` [tip: x86/cpu] " tip-bot2 for Kim Phillips
2023-01-24 21:37 ` [PATCH v9 0/8] x86/cpu, kvm: Support AMD Automatic IBRS Sean Christopherson
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=20230225000931.wrednfun4jifkqau@treble \
--to=jpoimboe@kernel.org \
--cc=aik@amd.com \
--cc=boris.ostrovsky@oracle.com \
--cc=bp@alien8.de \
--cc=corbet@lwn.net \
--cc=dave.hansen@linux.intel.com \
--cc=dwmw@amazon.co.uk \
--cc=gregkh@linuxfoundation.org \
--cc=hpa@zytor.com \
--cc=jgross@suse.com \
--cc=joao.m.martins@oracle.com \
--cc=kim.phillips@amd.com \
--cc=konrad.wilk@oracle.com \
--cc=kvm@vger.kernel.org \
--cc=linux-doc@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=pbonzini@redhat.com \
--cc=peterz@infradead.org \
--cc=seanjc@google.com \
--cc=tglx@linutronix.de \
--cc=thomas.lendacky@amd.com \
--cc=tony.luck@intel.com \
--cc=x86@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;
as well as URLs for NNTP newsgroup(s).