From: Reiji Watanabe <reijiw@google.com>
To: Borislav Petkov <bp@alien8.de>
Cc: Ramakrishna Saripalli <rsaripal@amd.com>,
linux-kernel@vger.kernel.org, x86@kernel.org, tglx@linutronix.de,
mingo@redhat.com, hpa@zytor.com, Jonathan Corbet <corbet@lwn.net>,
bsd@redhat.com
Subject: Re: [PATCH v4 1/1] x86/cpufeatures: Implement Predictive Store Forwarding control.
Date: Fri, 30 Apr 2021 14:03:07 -0700 [thread overview]
Message-ID: <CAAeT=FxqM5P+6U8vBywuvnaJ0s4sWdRHK2fvn4b1zf5mMLKReg@mail.gmail.com> (raw)
In-Reply-To: <YIxhCSt6t5U/Eldb@zn.tnic>
> > Then, it would be a problem if its guests want to use PSFD looking at
> > x86_virt_spec_ctrl().
>
> Well, will they want to do that? If so, why? Use case?
>
> We decided to do this lite version to give people the opportunity to
> evaluate whether there's a need to make full-blown mitigation-like,
> per-thread thing like the rest of the mitigations in bugs.c or leave it
> to be a chicken-bit thing.
>
> So do you have any particular use case in mind or are you simply poking
> holes in this?
I didn't mean per-thread thing but per-VM and I understand
the per-thread thing was dropped.
But, doesn't the current plan include even the per-VM control ?
Since the comments below from Ramakrishna (yesterday) mentioned
KVM/virtualization support, I assumed that there would be
per-VM control even in the current plan.
--------------------------------------------------------------
But I did test with KVM (with my patch that is not here) and I do not see
issues (meaning user space guest in QEMU is seeing PSF CPUID guest capability)
--------------------------------------------------------------
Yes this feature is needed for KVM/virtualization support.
--------------------------------------------------------------
Could you please clarify ?
Thanks,
Reiji
next prev parent reply other threads:[~2021-04-30 21:03 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-30 13:17 [PATCH v4 0/1] Introduce support for PSF control Ramakrishna Saripalli
2021-04-30 13:17 ` [PATCH v4 1/1] x86/cpufeatures: Implement Predictive Store Forwarding control Ramakrishna Saripalli
2021-04-30 14:50 ` Tom Lendacky
2021-04-30 14:56 ` Saripalli, RK
2021-04-30 19:42 ` Reiji Watanabe
2021-04-30 19:52 ` Saripalli, RK
2021-05-01 1:50 ` Reiji Watanabe
2021-05-04 21:01 ` Saripalli, RK
2021-05-04 22:11 ` Reiji Watanabe
2021-05-05 1:13 ` Saripalli, RK
2021-04-30 19:56 ` Borislav Petkov
2021-04-30 21:03 ` Reiji Watanabe [this message]
2021-04-30 21:11 ` Borislav Petkov
2021-05-01 1:01 ` Reiji Watanabe
2021-05-05 0:11 ` Pawan Gupta
2021-05-05 1:11 ` Saripalli, RK
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