From: Paolo Bonzini <pbonzini@redhat.com>
To: Bandan Das <bsd@redhat.com>, Wanpeng Li <wanpeng.li@hotmail.com>
Cc: Jan Kiszka <jan.kiszka@siemens.com>,
Wincy Van <fanwenyi0529@gmail.com>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] KVM: introduce __vmx_flush_tlb to handle specific vpid
Date: Fri, 25 Sep 2015 10:01:53 +0200 [thread overview]
Message-ID: <5604FF71.6090109@redhat.com> (raw)
In-Reply-To: <jpg8u7vkd8k.fsf@linux.bootlegged.copy>
On 24/09/2015 18:12, Bandan Das wrote:
> Not sure myself what's the right thing to do but this may be undesirable
> in a nested environment. Assuming the processor supports global invalidation
> only, this seems like a easy way for the nested guest to invalidate *all*
> mappings - even the L1 specific mappings.
It's not a great thing but it's already what happens if you do a global
INVEPT (it calls vmx_flush_tlb, which results in a global INVVPID if the
single-context variant is not supported).
Even without nested virt a single guest could slow down all other guests
just by triggering frequent TLB flushes (e.g. by moving around a ROM BAR
thousands of times per second).
It would help to know _which_ processors actually don't support
single-context INVVPIDs...
Paolo
prev parent reply other threads:[~2015-09-25 8:02 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-09-23 10:26 [PATCH 1/2] KVM: introduce __vmx_flush_tlb to handle specific vpid Wanpeng Li
2015-09-24 16:12 ` Bandan Das
2015-09-25 3:01 ` Wanpeng Li
2015-09-25 8:01 ` Paolo Bonzini [this message]
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