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[PATCH 2/2] xen/domain: Save PMU counters to mdcr_el2
- To: <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Daisuke Nishimura <nishimura@xxxxxxxxxxxxx>
- Date: Tue, 10 Nov 2026 14:31:42 +0900
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- Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Bertrand Marquis <bertrand.marquis@xxxxxxx>, Michal Orzel <michal.orzel@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>, Leonid Komarianskyi <leonid_komarianskyi@xxxxxxxx>
- Delivery-date: Tue, 10 Nov 2026 05:34:11 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
From: Leonid Komarianskyi <leonid_komarianskyi@xxxxxxxx>
According to arm documentation
"When EL2 is implemented and enabled for the current
Security state, reads of this field from EL1
and EL0 return the value of MDCR_EL2.HPMN."
To be able to use PMU counters from guest domain, the
counters should be read from pmcr_el0 register and saved
to mdcr_el2.
Signed-off-by: Leonid Komarianskyi <leonid_komarianskyi@xxxxxxxx>
Signed-off-by: Volodymyr Babchuk <volodymyr_babchuk@xxxxxxxx>
Signed-off-by: Daisuke Nishimura <nishimura@xxxxxxxxxxxxx>
---
(cherry picked from commit 8711910a8fb66eb454172a9e6427aaf62bfc3a80
xen-troops) [Daisuke: modified to follow the upstream changes:
- adapted to b836ef686e ("xen/arm: Hide PMU registers from the
guest, when the vPMU feature is disabled"), which moved this
code under is_vpmu_domain()
- instead of reading PMCR_EL0 per vCPU here, use
system_pmu_num_cntrs, the minimum number of counters across
all online CPUs, so the reported value is valid no matter
which CPU the vCPU runs on]
---
xen/arch/arm/domain.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/xen/arch/arm/domain.c b/xen/arch/arm/domain.c
index 34b5a85f9f..f864327006 100644
--- a/xen/arch/arm/domain.c
+++ b/xen/arch/arm/domain.c
@@ -503,6 +503,8 @@ int arch_vcpu_create(struct vcpu *v)
v->arch.mdcr_el2 = HDCR_TDRA | HDCR_TDOSA | HDCR_TDA;
if ( !is_vpmu_domain(v->domain) )
v->arch.mdcr_el2 |= HDCR_TPM | HDCR_TPMCR;
+ else
+ v->arch.mdcr_el2 |= system_pmu_num_cntrs;
if ( (rc = vcpu_vgic_init(v)) != 0 )
goto fail;
--
2.43.0
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