From: Sean Christopherson <sean.j.christopherson@intel.com>
To: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
"Paolo Bonzini" <pbonzini@redhat.com>,
"Radim Krčmář" <rkrcmar@redhat.com>,
"Roman Kagan" <rkagan@virtuozzo.com>
Subject: Re: [PATCH v2] x86: kvm: hyper-v: deal with buggy TLB flush requests from WS2012
Date: Tue, 23 Apr 2019 06:59:34 -0700 [thread overview]
Message-ID: <20190423135934.GA10720@linux.intel.com> (raw)
In-Reply-To: <20190423131537.9298-1-vkuznets@redhat.com>
On Tue, Apr 23, 2019 at 03:15:37PM +0200, Vitaly Kuznetsov wrote:
> It was reported that with some special Multi Processor Group configuration,
> e.g:
> bcdedit.exe /set groupsize 1
> bcdedit.exe /set maxgroup on
> bcdedit.exe /set groupaware on
> for a 16-vCPU guest WS2012 shows BSOD on boot when PV TLB flush mechanism
> is in use.
>
> Tracing kvm_hv_flush_tlb immediately reveals the issue:
>
> kvm_hv_flush_tlb: processor_mask 0x0 address_space 0x0 flags 0x2
>
> The only flag set in this request is HV_FLUSH_ALL_VIRTUAL_ADDRESS_SPACES,
> however, processor_mask is 0x0 and no HV_FLUSH_ALL_PROCESSORS is specified.
> We don't flush anything and apparently it's not what Windows expects.
>
> TLFS doesn't say anything about such requests and newer Windows versions
> seem to be unaffected. This all feels like a WS2012 bug, which is, however,
> easy to workaround in KVM: let's flush everything when we see an empty
> flush request, over-flushing doesn't hurt.
>
> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> ---
Reviewed-by: Sean Christopherson <sean.j.christopherson@intel.com>
prev parent reply other threads:[~2019-04-23 13:59 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-23 13:15 [PATCH v2] x86: kvm: hyper-v: deal with buggy TLB flush requests from WS2012 Vitaly Kuznetsov
2019-04-23 13:59 ` Sean Christopherson [this message]
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