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Re: [XEN][PATCH v3] x86: make Viridian support optional


  • To: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
  • From: Grygorii Strashko <grygorii_strashko@xxxxxxxx>
  • Date: Thu, 18 Sep 2025 18:15:16 +0300
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  • Cc: Sergiy Kibrik <Sergiy_Kibrik@xxxxxxxx>, Jan Beulich <jbeulich@xxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Paul Durrant <paul@xxxxxxx>, Alejandro Vallejo <alejandro.garciavallejo@xxxxxxx>
  • Delivery-date: Thu, 18 Sep 2025 15:15:27 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

Hi All,

On 16.09.25 16:41, Grygorii Strashko wrote:
From: Sergiy Kibrik <Sergiy_Kibrik@xxxxxxxx>

Add config option HVM_VIRIDIAN that covers viridian code within HVM.
Calls to viridian functions guarded by is_viridian_domain() and related macros.
Having this option may be beneficial by reducing code footprint for systems
that are not using Hyper-V.

[grygorii_strashko@xxxxxxxx: fixed NULL pointer deref in
viridian_save_domain_ctxt()]
Signed-off-by: Sergiy Kibrik <Sergiy_Kibrik@xxxxxxxx>
Signed-off-by: Grygorii Strashko <grygorii_strashko@xxxxxxxx>
---
changes in v3:
- fixed NULL pointer deref in viridian_save_domain_ctxt() reported for v2,
   which caused v2 revert by commit 1fffcf10cd71 ("Revert "x86: make Viridian
   support optional"")

v2: 
https://patchwork.kernel.org/project/xen-devel/patch/20250321092633.3982645-1-Sergiy_Kibrik@xxxxxxxx/

  xen/arch/x86/hvm/Kconfig              | 10 ++++++++++
  xen/arch/x86/hvm/Makefile             |  2 +-
  xen/arch/x86/hvm/hvm.c                | 27 ++++++++++++++++++---------
  xen/arch/x86/hvm/viridian/viridian.c  |  8 ++++----
  xen/arch/x86/hvm/vlapic.c             | 11 +++++++----
  xen/arch/x86/include/asm/hvm/domain.h |  2 ++
  xen/arch/x86/include/asm/hvm/hvm.h    |  3 ++-
  xen/arch/x86/include/asm/hvm/vcpu.h   |  2 ++
  8 files changed, 46 insertions(+), 19 deletions(-)

diff --git a/xen/arch/x86/hvm/Kconfig b/xen/arch/x86/hvm/Kconfig
index 5cb9f2904255..cf2726ef6bc3 100644
--- a/xen/arch/x86/hvm/Kconfig
+++ b/xen/arch/x86/hvm/Kconfig
@@ -62,6 +62,16 @@ config ALTP2M
If unsure, stay with defaults. +config HVM_VIRIDIAN
+       bool "Hyper-V enlightenments for guests" if EXPERT
+       default y
+       help
+         Support optimizations for Hyper-V guests such as faster hypercalls,
+         efficient timer and interrupt handling, and enhanced paravirtualized
+         I/O. This is to improve performance and compatibility of Windows VMs.
+
+         If unsure, say Y.
+

Actually there is a question for x86 Experts -
Does it make sense to have HVM_VIRIDIAN enabled without enabled 
AMD_SVM/INTEL_VMX Virtualization extensions?

--
Best regards,
-grygorii




 


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