From: Paolo Bonzini <pbonzini@redhat.com>
To: Jan Kiszka <jan.kiszka@web.de>
Cc: Anthony Liguori <aliguori@us.ibm.com>,
kvm@vger.kernel.org, Gleb Natapov <gleb@redhat.com>,
Marcelo Tosatti <mtosatti@redhat.com>,
qemu-devel <qemu-devel@nongnu.org>, Avi Kivity <avi@redhat.com>
Subject: Re: [PATCH 3/6] kvmvapic: Introduce TPR access optimization for Windows guests
Date: Thu, 09 Feb 2012 18:20:38 +0100 [thread overview]
Message-ID: <4F340066.9070108@redhat.com> (raw)
In-Reply-To: <4F33F50C.2050104@web.de>
On 02/09/2012 05:32 PM, Jan Kiszka wrote:
> > I mean just check kpcr.self.
>
> Yes, clear, but that means that Windows must have initialized FS.base to
> point to the KPCR also in UP mode. Is that really the case? E.g. when
> ACPI is off?! I wonder if that explains the reported bug of qemu-kvm
> with -no-acpi and in-kernel irqchip...
Yes, it does. It's used by some fast-path kernel APIs, and indeed the
canonical way to find the KPCR base from ring 0 is to look at FS:[1Ch].
Similarly in userspace you can find the thread information block at
FS:[sizeof(void*)*6], and FS:[1Ch] is something else. But your code
cannot be reached from userspace, so that's always fine.
Paolo
WARNING: multiple messages have this Message-ID (diff)
From: Paolo Bonzini <pbonzini@redhat.com>
To: Jan Kiszka <jan.kiszka@web.de>
Cc: Anthony Liguori <aliguori@us.ibm.com>,
kvm@vger.kernel.org, Gleb Natapov <gleb@redhat.com>,
Marcelo Tosatti <mtosatti@redhat.com>,
qemu-devel <qemu-devel@nongnu.org>, Avi Kivity <avi@redhat.com>
Subject: Re: [Qemu-devel] [PATCH 3/6] kvmvapic: Introduce TPR access optimization for Windows guests
Date: Thu, 09 Feb 2012 18:20:38 +0100 [thread overview]
Message-ID: <4F340066.9070108@redhat.com> (raw)
In-Reply-To: <4F33F50C.2050104@web.de>
On 02/09/2012 05:32 PM, Jan Kiszka wrote:
> > I mean just check kpcr.self.
>
> Yes, clear, but that means that Windows must have initialized FS.base to
> point to the KPCR also in UP mode. Is that really the case? E.g. when
> ACPI is off?! I wonder if that explains the reported bug of qemu-kvm
> with -no-acpi and in-kernel irqchip...
Yes, it does. It's used by some fast-path kernel APIs, and indeed the
canonical way to find the KPCR base from ring 0 is to look at FS:[1Ch].
Similarly in userspace you can find the thread information block at
FS:[sizeof(void*)*6], and FS:[1Ch] is something else. But your code
cannot be reached from userspace, so that's always fine.
Paolo
next prev parent reply other threads:[~2012-02-09 17:20 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-02-05 12:39 [PATCH 0/6] uq/master: TPR access optimization for Windows guests Jan Kiszka
2012-02-05 12:39 ` [Qemu-devel] " Jan Kiszka
2012-02-05 12:39 ` [PATCH 1/6] target-i386: Add infrastructure for reporting TPR MMIO accesses Jan Kiszka
2012-02-05 12:39 ` [Qemu-devel] " Jan Kiszka
2012-02-05 12:39 ` [PATCH 2/6] kvmvapic: Add option ROM Jan Kiszka
2012-02-05 12:39 ` [Qemu-devel] " Jan Kiszka
2012-02-05 12:39 ` [PATCH 3/6] kvmvapic: Introduce TPR access optimization for Windows guests Jan Kiszka
2012-02-05 12:39 ` [Qemu-devel] " Jan Kiszka
2012-02-09 8:35 ` [Qemu-devel] subpages with memory region aliases (was: [PATCH 3/6] kvmvapic: Introduce TPR access optimization for Windows guests) Jan Kiszka
2012-02-09 9:32 ` [Qemu-devel] subpages with memory region aliases Avi Kivity
2012-02-09 14:23 ` Jan Kiszka
2012-02-09 15:05 ` Avi Kivity
2012-02-09 15:18 ` [PATCH 3/6] kvmvapic: Introduce TPR access optimization for Windows guests Avi Kivity
2012-02-09 15:18 ` [Qemu-devel] " Avi Kivity
2012-02-09 15:39 ` Jan Kiszka
2012-02-09 15:39 ` [Qemu-devel] " Jan Kiszka
2012-02-09 16:00 ` Avi Kivity
2012-02-09 16:00 ` [Qemu-devel] " Avi Kivity
2012-02-09 16:32 ` Jan Kiszka
2012-02-09 16:32 ` [Qemu-devel] " Jan Kiszka
2012-02-09 16:47 ` Avi Kivity
2012-02-09 16:47 ` [Qemu-devel] " Avi Kivity
2012-02-09 17:24 ` Jan Kiszka
2012-02-09 17:24 ` [Qemu-devel] " Jan Kiszka
2012-02-09 17:20 ` Paolo Bonzini [this message]
2012-02-09 17:20 ` Paolo Bonzini
2012-02-09 18:01 ` Jan Kiszka
2012-02-09 18:01 ` [Qemu-devel] " Jan Kiszka
2012-02-05 12:39 ` [PATCH 4/6] kvmvapic: Simplify mp/up_set_tpr Jan Kiszka
2012-02-05 12:39 ` [Qemu-devel] " Jan Kiszka
2012-02-05 12:39 ` [PATCH 5/6] optionsrom: Reserve space for checksum Jan Kiszka
2012-02-05 12:39 ` [Qemu-devel] " Jan Kiszka
2012-02-05 12:39 ` [PATCH 6/6] kvmvapic: Use optionrom helpers Jan Kiszka
2012-02-05 12:39 ` [Qemu-devel] " Jan Kiszka
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