[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [XEN][PATCH] x86/hvm: revise "cpu_has_vmx" usage for !CONFIG_INTEL_VMX case
- To: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Grygorii Strashko <grygorii_strashko@xxxxxxxx>
- Date: Wed, 12 Nov 2025 22:25:31 +0200
- Arc-authentication-results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=epam.com; dmarc=pass action=none header.from=epam.com; dkim=pass header.d=epam.com; arc=none
- Arc-message-signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector10001; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=vEc11qj6VNeS+qQGExmT8/5BSuSV1Y4Xhy3y9veJe4s=; b=WQUw6HMwezkwmx6N0RicXsvZvNxpgeBVCCA6hYakiNWQLKPwwhKx/rgY3y7pWv2XWJCkI0TbPaDad7VuODux3KqkGCJ8eSs6nPfEJRtEJZeZ6vwTxu1+TvZM+IvkFLvZ07fdpSO4zRr/fukpXGLCJNobYdLZ94aQ8kF8GNOAJSrCpZUTdPIpZJcOx1gypjYlKmGjSGfGTTwqQEwJY9nhfoq3R1UvKWweiaQLlx5Hk3M/Uy+UtOVlrl387jcHQlK2QKV/rK5T7jZngWypBfpt3IgFWQgoVp2CFuEPTfJoHl15cxarejSsxgstcNWxl5Ksj//BnYjzgg/I2gLW6IIi+w==
- Arc-seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=IgLML+ayXDhYMs6c74tVIxzoola2z6s/dmRyZoC5033WvueQQQKEluPX5MA8oaeQFPS+DVPEwm+04ZcuoZBeHv0MDabUyxaA6aK7pPuEs1RwTz1UwouDdNqT+VghLe8CK5MnF9itBaa82ZFf/R7DtGq6mzZ4ehyJuPoGTkbWU9qgL3baAT60NQC32gcEQDLfEGdljY3TTjemVNLe0Owo1eknWEAUdj3oVW27zP/OSiOMtdKOIlQBR2IyUJ7KVV0puvTSs/C/o36u0I/TdlqeGerse8Mp3TeOvfV9iUa0m1ct/bQr7DA7wR4Rjx+HyVi8hf8M/clcW30IZonbT/03Aw==
- Authentication-results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=epam.com;
- Cc: Jan Beulich <jbeulich@xxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Alejandro Vallejo <alejandro.garciavallejo@xxxxxxx>
- Delivery-date: Wed, 12 Nov 2025 20:25:35 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
Hi
Could it be merged if no other comments, please?
On 24.09.25 13:14, Grygorii Strashko wrote:
From: Grygorii Strashko <grygorii_strashko@xxxxxxxx>
Since commit b99227347230 ("x86: Fix AMD_SVM and INTEL_VMX dependency") the
HVM Intel VT-x support can be disabled, but it still keeps VMX
code partially built-in. Particularly in HVM code there are two places:
1) hvm/dom0_build.c
dom0_construct_pvh()->pvh_populate_p2m()
...
if ( cpu_has_vmx && paging_mode_hap(d) && !vmx_unrestricted_guest(v) )
{
...
[unreachable for !cpu_has_vmx case]
rc = pvh_setup_vmx_realmode_helpers(d);
pvh_setup_vmx_realmode_helpers() allocates memory and configures
HVM_PARAM_VM86_TSS_SIZED
HVM_PARAM_IDENT_PT
2) hvm/hvm.c
hvm_set_param()
...
case HVM_PARAM_IDENT_PT:
if ( !paging_mode_hap(d) || !cpu_has_vmx )
{
d->arch.hvm.params[index] = value;
break;
}
[unreachable for !cpu_has_vmx case]
...
Hence HVM_PARAM_IDENT_PT/HVM_PARAM_VM86_TSS_SIZED are used only by VMX code
above code become unreachable in !cpu_has_vmx case and can be optimazed
when !CONFIG_INTEL_VMX.
Replace "cpu_has_vmx" with using_vmx() to account !CONFIG_INTEL_VMX and allow
compiler DCE to optimize code.
Signed-off-by: Grygorii Strashko <grygorii_strashko@xxxxxxxx>
---
add/remove: 0/0 grow/shrink: 0/2 up/down: 0/-604 (-604)
Function old new delta
hvm_set_param 1602 1473 -129
dom0_construct_pvh 4438 3963 -475
Total: Before=3567191, After=3566587, chg -0.02%
xen/arch/x86/hvm/dom0_build.c | 2 +-
xen/arch/x86/hvm/hvm.c | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/xen/arch/x86/hvm/dom0_build.c b/xen/arch/x86/hvm/dom0_build.c
index 5551f9044836..5ac2cf8394d8 100644
--- a/xen/arch/x86/hvm/dom0_build.c
+++ b/xen/arch/x86/hvm/dom0_build.c
@@ -473,7 +473,7 @@ static int __init pvh_populate_p2m(struct domain *d)
}
}
- if ( cpu_has_vmx && paging_mode_hap(d) && !vmx_unrestricted_guest(v) )
+ if ( using_vmx() && paging_mode_hap(d) && !vmx_unrestricted_guest(v) )
{
/*
* Since Dom0 cannot be migrated, we will only setup the
diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 95a80369b9b8..70331aeec9a0 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -4302,7 +4302,7 @@ static int hvm_set_param(struct domain *d, uint32_t
index, uint64_t value)
* Only actually required for VT-x lacking unrestricted_guest
* capabilities. Short circuit the pause if possible.
*/
- if ( !paging_mode_hap(d) || !cpu_has_vmx )
+ if ( !paging_mode_hap(d) || !using_vmx() )
{
d->arch.hvm.params[index] = value;
break;
--
Best regards,
-grygorii
|
