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Re: [PATCH for-4.21??? 3/3] x86/vLAPIC: properly support the CMCI LVT
- To: Jan Beulich <jbeulich@xxxxxxxx>
- From: Grygorii Strashko <grygorii_strashko@xxxxxxxx>
- Date: Tue, 14 Oct 2025 17:12:03 +0300
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- Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Andrew Cooper <amc96@xxxxxxxx>, Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Tue, 14 Oct 2025 14:12:20 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 09.10.25 18:37, Jan Beulich wrote:
On 09.10.2025 17:08, Grygorii Strashko wrote:
On 08.10.25 15:09, Jan Beulich wrote:
--- a/xen/arch/x86/hvm/vlapic.c
+++ b/xen/arch/x86/hvm/vlapic.c
@@ -31,10 +31,13 @@
#include <public/hvm/ioreq.h>
#include <public/hvm/params.h>
-#define LVT_BIAS(reg) (((reg) - APIC_LVTT) >> 4)
+#include <../cpu/mcheck/x86_mca.h> /* MCG_CMCI_P */
This include... You probably do not like it also
It is dependency outside HVM code.
I've been thinking about something like vlapic->caps which can be filed before
vlapic_init()
or passed as parameter, but seems x86 toolstack is considered to be able
overwrite anything,
including v->arch.vmce.
Seems, no better options here.
Same here, hence why I used it despite not liking it.
@@ -697,8 +701,17 @@ int guest_rdmsr_x2apic(const struct vcpu
return X86EMUL_EXCEPTION;
offset = reg << 4;
- if ( offset == APIC_ICR )
+ switch ( offset )
+ {
+ case APIC_ICR:
high = (uint64_t)vlapic_read_aligned(vlapic, APIC_ICR2) << 32;
+ break;
+
+ case APIC_CMCI:
+ if ( !(v->arch.vmce.mcg_cap & MCG_CMCI_P) )
Could it be done using wrapper, like vmce_has_cmci()?
As this is Intel specific it's candidate to be opt-out eventually.
Possible. I wanted to limit the churn, hence why I preferred not to introduce
a wrapper. Such an abstraction I wouldn't like to be a function taking a vCPU;
really this should be a domain property imo.
My intention was to limit spreading direct access to "vmce" data over vlapic
code:
static bool vlapic_has_cmci(const struct vcpu *v)
{
return v->arch.vmce.mcg_cap & MCG_CMCI_P;
}
Just expressing opinion.
--
Best regards,
-grygorii
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