Re: [PATCH] When switching to a vm8086 task, load segments as 16-bit (v2)
On 08/11/2009 11:57 PM, Anthony Liguori wrote: According to 16.2.5 in the SDM, eflags.vm in the tss is consulted before loading and new segments. If eflags.vm == 1, then the segments are treated as 16-bit segments. The LDTR and TR are not normally available in vm86 mode so if they happen to somehow get loaded, they need to be treated as 32-bit segments. This fixes an invalid vmentry failure in a custom OS that was happening after a task switch into vm8086 mode. Since the segments were being mistakenly treated as 32-bit, we loaded garbage state. Applied, thanks. -- error compiling committee.c: too many arguments to function -- To unsubscribe from this list: send the line unsubscribe kvm in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH] When switching to a vm8086 task, load segments as 16-bit (v2)
On 08/11/2009 11:57 PM, Anthony Liguori wrote: According to 16.2.5 in the SDM, eflags.vm in the tss is consulted before loading and new segments. If eflags.vm == 1, then the segments are treated as 16-bit segments. The LDTR and TR are not normally available in vm86 mode so if they happen to somehow get loaded, they need to be treated as 32-bit segments. This fixes an invalid vmentry failure in a custom OS that was happening after a task switch into vm8086 mode. Since the segments were being mistakenly treated as 32-bit, we loaded garbage state. I'm getting a Vista x64 installer failure on reboot with this. One possibility is that -get_rflags() is returning the mangled flags state (we add vm86 for real mode), which confuses the new code. -- error compiling committee.c: too many arguments to function -- To unsubscribe from this list: send the line unsubscribe kvm in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH] When switching to a vm8086 task, load segments as 16-bit (v2)
On 08/12/2009 03:11 PM, Avi Kivity wrote: On 08/11/2009 11:57 PM, Anthony Liguori wrote: According to 16.2.5 in the SDM, eflags.vm in the tss is consulted before loading and new segments. If eflags.vm == 1, then the segments are treated as 16-bit segments. The LDTR and TR are not normally available in vm86 mode so if they happen to somehow get loaded, they need to be treated as 32-bit segments. This fixes an invalid vmentry failure in a custom OS that was happening after a task switch into vm8086 mode. Since the segments were being mistakenly treated as 32-bit, we loaded garbage state. I'm getting a Vista x64 installer failure on reboot with this. One possibility is that -get_rflags() is returning the mangled flags state (we add vm86 for real mode), which confuses the new code. That's indeed the case, I'm testing a patch now. -- error compiling committee.c: too many arguments to function -- To unsubscribe from this list: send the line unsubscribe kvm in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH] When switching to a vm8086 task, load segments as 16-bit (v2)
Avi Kivity wrote: On 08/12/2009 03:11 PM, Avi Kivity wrote: On 08/11/2009 11:57 PM, Anthony Liguori wrote: According to 16.2.5 in the SDM, eflags.vm in the tss is consulted before loading and new segments. If eflags.vm == 1, then the segments are treated as 16-bit segments. The LDTR and TR are not normally available in vm86 mode so if they happen to somehow get loaded, they need to be treated as 32-bit segments. This fixes an invalid vmentry failure in a custom OS that was happening after a task switch into vm8086 mode. Since the segments were being mistakenly treated as 32-bit, we loaded garbage state. I'm getting a Vista x64 installer failure on reboot with this. One possibility is that -get_rflags() is returning the mangled flags state (we add vm86 for real mode), which confuses the new code. That's indeed the case, I'm testing a patch now. While the code looks nicer with the second patch, the fact that get_rflags() does a vmcs_read() seems 7 times more than before seems unfortunate. -- Regards, Anthony Liguori -- To unsubscribe from this list: send the line unsubscribe kvm in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH] When switching to a vm8086 task, load segments as 16-bit (v2)
On 08/12/2009 04:15 PM, Anthony Liguori wrote: While the code looks nicer with the second patch, the fact that get_rflags() does a vmcs_read() seems 7 times more than before seems unfortunate. We can add kvm_rflags_read(), see kvm_cache_regs.h. In any case, it's purely academic since task switches are rare and incredibly slow anyway (you have to vmcs_write() the entire register set for one). -- error compiling committee.c: too many arguments to function -- To unsubscribe from this list: send the line unsubscribe kvm in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH] When switching to a vm8086 task, load segments as 16-bit (v2)
Avi Kivity wrote: On 08/12/2009 04:15 PM, Anthony Liguori wrote: While the code looks nicer with the second patch, the fact that get_rflags() does a vmcs_read() seems 7 times more than before seems unfortunate. We can add kvm_rflags_read(), see kvm_cache_regs.h. In any case, it's purely academic since task switches are rare and incredibly slow anyway (you have to vmcs_write() the entire register set for one). Fair enough. -- Regards, Anthony Liguori -- To unsubscribe from this list: send the line unsubscribe kvm in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
