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Re: [Xen-devel] [PATCH][v9 4/6] xen/hvm: Xen PV extension of HVM initial

To: Sheng Yang <sheng@xxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH][v9 4/6] xen/hvm: Xen PV extension of HVM initialization
From: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Date: Fri, 12 Mar 2010 12:35:53 -0800
Cc: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, Ian Campbell <Ian.Campbell@xxxxxxxxxx>, "Yaozu \(Eddie\) Dong" <eddie.dong@xxxxxxxxx>, linux-kernel@xxxxxxxxxxxxxxx, Ian Pratt <Ian.Pratt@xxxxxxxxxxxxx>, Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
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On 03/11/2010 06:57 PM, Sheng Yang wrote:
The PV extended HVM(once known as Hybrid) is started from real mode like
HVM guest, but also with a component based PV feature selection(e.g. PV halt,
PV timer, event channel, then PV drivers). So guest can takes the advantages
of both H/W virtualization and Para-Virtualization.

This patch introduced the PV extension of HVM guest initialization.

Guest would detect the capability using CPUID 0x40000002.edx, then call
HVMOP_enable_pv hypercall to enable pv support in hypervisor.

Signed-off-by: Sheng Yang<sheng@xxxxxxxxxxxxxxx>
Signed-off-by: Yaozu (Eddie) Dong<eddie.dong@xxxxxxxxx>
  arch/x86/include/asm/xen/cpuid.h      |    5 +
  arch/x86/include/asm/xen/hypervisor.h |   12 +++
  arch/x86/xen/Kconfig                  |    4 +
  arch/x86/xen/Makefile                 |    1 +
  arch/x86/xen/hvmpv.c                  |  135 +++++++++++++++++++++++++++++++++
  include/xen/interface/hvm/hvm_op.h    |    8 ++
  6 files changed, 165 insertions(+), 0 deletions(-)
  create mode 100644 arch/x86/xen/hvmpv.c

diff --git a/arch/x86/include/asm/xen/cpuid.h b/arch/x86/include/asm/xen/cpuid.h
index 8787f03..b3a0b3a 100644
--- a/arch/x86/include/asm/xen/cpuid.h
+++ b/arch/x86/include/asm/xen/cpuid.h
@@ -65,4 +65,9 @@

+#define _XEN_CPUID_FEAT2_HVM_PV 0
+#define XEN_CPUID_FEAT2_HVM_PV (1u<<0)
+#define XEN_CPUID_FEAT2_HVM_PV_CLOCK (1u<<1)
  #endif /* __XEN_PUBLIC_ARCH_X86_CPUID_H__ */
diff --git a/arch/x86/include/asm/xen/hypervisor.h 
index d5b7e90..7569f64 100644
--- a/arch/x86/include/asm/xen/hypervisor.h
+++ b/arch/x86/include/asm/xen/hypervisor.h
@@ -55,6 +55,18 @@ extern enum xen_domain_type xen_domain_type;
  #define xen_hvm_domain()      (xen_domain()&&                 \
                                 xen_domain_type == XEN_HVM_DOMAIN)

+#define XEN_HVM_PV_CLOCK_ENABLED   (1u<<  0)

Why is this flag needed? As far as I understand it, there's no real underlying hypervisor change needed to make HVM access to pv clock possible; its just a field in the shared_info's vcpu struct after all. Even if you enable this feature unconditionally, the user can still control whether the Xen clocksource is used with the "clocksource=" kernel command-line parameter.

Also, there's nothing about this which is 64-bit specific is there?


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