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List: qemu-devel
Subject: [Qemu-devel] Re: [PATCH] Save 64-bit of the IA-32e capable sysenter
From: Avi Kivity <avi () qumranet ! com>
Date: 2008-07-31 10:07:27
Message-ID: 48918EDF.5000709 () qumranet ! com
[Download RAW message or body]
Alexander Graf wrote:
> Hi,
>
> When transitioning from KVM to the qemu userspace, we try to get and
> push a whole bunch of MSR values, including the SYSENTER ones. While
> this is basically a good idea, qemu doesn't know anything about
> SYSENTER on x86_64, which is an additional feature only available on
> Intel CPUs and thus defines SYSENTER_EIP and SYSENTER_ESP as 32-bit
> values.
>
> Because we're saving/restoring the SYSENTER values on transitions to
> userspace and the values in env->cpu only hold 32 bits, they get
> truncated to 32-bit. The easiest way around this is to widen the
> fields to 64 bits. This should not disturb the current functionality,
> but allows us to run 32-bit code on x86_64 using VMX.
>
> As this is KVM specific for now, I'll only CC the qemu mailinglist,
> but wouldn't encourage qemu to take the patch for now, as it's not
> necessary when emulating an AMD CPU.
>
Applied, thanks. I imagine save/restore support needs updating as
well? That should go into qemuy btw since maintaining the save/restore
format across forks isn't possible.
--
error compiling committee.c: too many arguments to function
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