[Xen-devel] [PATCH v4 04/19] xen/arm: Avoid setting/clearing HCR_RW at every context switch

[Wei Chen <Wei.Chen@xxxxxxx>]

The HCR_EL2 flags for 64-bit and 32-bit domains are different. But
when we initialized the HCR_EL2 for vcpu0 of Dom0 and all vcpus of
DomU in vcpu_initialise, we didn't know the domain's address size
information. We had to use compatible flags to initialize HCR_EL2,
and set HCR_RW for 64-bit domain or clear HCR_RW for 32-bit domain
at every context switch.

But, after we added the HCR_EL2 to vcpu's context, this behaviour
seems a little fussy. We can update the HCR_RW bit in vcpu's context
as soon as we get the domain's address size to avoid setting/clearing
HCR_RW at every context switch.

Signed-off-by: Wei Chen <Wei.Chen@xxxxxxx>
Acked-by: Julien Grall <julien.grall@xxxxxxx>
Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
---
 xen/arch/arm/arm64/domctl.c  | 6 ++++++
 xen/arch/arm/domain.c        | 5 +++++
 xen/arch/arm/domain_build.c  | 7 +++++++
 xen/arch/arm/p2m.c           | 5 -----
 xen/include/asm-arm/domain.h | 1 +
 5 files changed, 19 insertions(+), 5 deletions(-)

diff --git a/xen/arch/arm/arm64/domctl.c b/xen/arch/arm/arm64/domctl.c
index 44e1e7b..ab8781f 100644
--- a/xen/arch/arm/arm64/domctl.c
+++ b/xen/arch/arm/arm64/domctl.c
@@ -14,6 +14,8 @@
 
 static long switch_mode(struct domain *d, enum domain_type type)
 {
+    struct vcpu *v;
+
     if ( d == NULL )
         return -EINVAL;
     if ( d->tot_pages != 0 )
@@ -23,6 +25,10 @@ static long switch_mode(struct domain *d, enum domain_type 
type)
 
     d->arch.type = type;
 
+    if ( is_64bit_domain(d) )
+        for_each_vcpu(d, v)
+            vcpu_switch_to_aarch64_mode(v);
+
     return 0;
 }
 
diff --git a/xen/arch/arm/domain.c b/xen/arch/arm/domain.c
index 5d18bb0..69c2854 100644
--- a/xen/arch/arm/domain.c
+++ b/xen/arch/arm/domain.c
@@ -537,6 +537,11 @@ void vcpu_destroy(struct vcpu *v)
     free_xenheap_pages(v->arch.stack, STACK_ORDER);
 }
 
+void vcpu_switch_to_aarch64_mode(struct vcpu *v)
+{
+    v->arch.hcr_el2 |= HCR_RW;
+}
+
 int arch_domain_create(struct domain *d, unsigned int domcr_flags,
                        struct xen_arch_domainconfig *config)
 {
diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
index de59e5f..3abacc0 100644
--- a/xen/arch/arm/domain_build.c
+++ b/xen/arch/arm/domain_build.c
@@ -2148,6 +2148,10 @@ int construct_dom0(struct domain *d)
         return -EINVAL;
     }
     d->arch.type = kinfo.type;
+
+    if ( is_64bit_domain(d) )
+        vcpu_switch_to_aarch64_mode(v);
+
 #endif
 
     allocate_memory(d, &kinfo);
@@ -2240,6 +2244,9 @@ int construct_dom0(struct domain *d)
             printk("Failed to allocate dom0 vcpu %d on pcpu %d\n", i, cpu);
             break;
         }
+
+        if ( is_64bit_domain(d) )
+            vcpu_switch_to_aarch64_mode(d->vcpu[i]);
     }
 
     return 0;
diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
index 83c4b7d..34d5776 100644
--- a/xen/arch/arm/p2m.c
+++ b/xen/arch/arm/p2m.c
@@ -137,11 +137,6 @@ void p2m_restore_state(struct vcpu *n)
     WRITE_SYSREG64(p2m->vttbr, VTTBR_EL2);
     isb();
 
-    if ( is_32bit_domain(n->domain) )
-        n->arch.hcr_el2 &= ~HCR_RW;
-    else
-        n->arch.hcr_el2 |= HCR_RW;
-
     WRITE_SYSREG(n->arch.sctlr, SCTLR_EL1);
     isb();
 
diff --git a/xen/include/asm-arm/domain.h b/xen/include/asm-arm/domain.h
index 7b1dacc..68185e2 100644
--- a/xen/include/asm-arm/domain.h
+++ b/xen/include/asm-arm/domain.h
@@ -268,6 +268,7 @@ struct arch_vcpu
 
 void vcpu_show_execution_state(struct vcpu *);
 void vcpu_show_registers(const struct vcpu *);
+void vcpu_switch_to_aarch64_mode(struct vcpu *);
 
 unsigned int domain_max_vcpus(const struct domain *);
 
-- 
2.7.4


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