Hi
Could it be merged if no other comments, please?
On 24.09.25 13:14, Grygorii Strashko wrote:
From: Grygorii Strashko <[email protected]>
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 <[email protected]>
---
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
