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Re: [Xen-devel] [PATCH v3 19/38] arm/p2m: Add HVMOP_altp2m_switch_p2m
Hello Sergej,
On 16/08/2016 23:16, Sergej Proskurin wrote:
Signed-off-by: Sergej Proskurin <proskurin@xxxxxxxxxxxxx>
---
Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
Cc: Julien Grall <julien.grall@xxxxxxx>
---
v3: Extended the function "altp2m_switch_domain_altp2m_by_id" so that if
the guest domain indirectly calles this function, the current vcpu also
changes the altp2m view without performing an explicit context switch.
Exchanged the check "altp2m_vttbr[idx] == INVALID_VTTBR" for
"altp2m_p2m[idx] == NULL" in "altp2m_switch_domain_altp2m_by_id".
---
xen/arch/arm/altp2m.c | 48 ++++++++++++++++++++++++++++++++++++++++++++
xen/arch/arm/hvm.c | 2 +-
xen/include/asm-arm/altp2m.h | 4 ++++
3 files changed, 53 insertions(+), 1 deletion(-)
diff --git a/xen/arch/arm/altp2m.c b/xen/arch/arm/altp2m.c
index c14ab0b..ba345b9 100644
--- a/xen/arch/arm/altp2m.c
+++ b/xen/arch/arm/altp2m.c
@@ -32,6 +32,54 @@ struct p2m_domain *altp2m_get_altp2m(struct vcpu *v)
return v->domain->arch.altp2m_p2m[index];
}
+int altp2m_switch_domain_altp2m_by_id(struct domain *d, unsigned int idx)
+{
+ struct vcpu *v;
+ int rc = -EINVAL;
+
+ if ( idx >= MAX_ALTP2M )
+ return rc;
+
+ domain_pause_except_self(d);
+
+ altp2m_lock(d);
+
+ if ( d->arch.altp2m_p2m[idx] != NULL )
+ {
+ for_each_vcpu( d, v )
+ if ( idx != altp2m_vcpu(v).p2midx )
Could you invert the condition to avoid another layer of nested if?
+ {
+ atomic_dec(&altp2m_get_altp2m(v)->active_vcpus);
+ altp2m_vcpu(v).p2midx = idx;
+ atomic_inc(&altp2m_get_altp2m(v)->active_vcpus);
+
+ /*
+ * In case it is the guest domain, which indirectly called this
+ * function, the current vcpu will not switch its context
+ * within the function "p2m_restore_state". That is, changing
+ * the altp2m_vcpu(v).p2midx will not lead to the requested
+ * altp2m switch on that specific vcpu. To achieve the desired
+ * behavior, we write to VTTBR_EL2 directly.
+ */
+ if ( v->domain == d && v == current )
v == current is enough.
+ {
+ struct p2m_domain *ap2m = d->arch.altp2m_p2m[idx];
+
+ WRITE_SYSREG64(ap2m->vttbr, VTTBR_EL2);
+ isb();
I don't like the open-coding of VTTBR_EL2. I would much prefer a
separate helper to update it.
+ }
+ }
+
+ rc = 0;
+ }
+
+ altp2m_unlock(d);
+
+ domain_unpause_except_self(d);
+
+ return rc;
+}
+
static void altp2m_vcpu_reset(struct vcpu *v)
{
struct altp2mvcpu *av = &altp2m_vcpu(v);
diff --git a/xen/arch/arm/hvm.c b/xen/arch/arm/hvm.c
index df973ef..9ac3422 100644
--- a/xen/arch/arm/hvm.c
+++ b/xen/arch/arm/hvm.c
@@ -132,7 +132,7 @@ static int do_altp2m_op(XEN_GUEST_HANDLE_PARAM(void) arg)
break;
case HVMOP_altp2m_switch_p2m:
- rc = -EOPNOTSUPP;
+ rc = altp2m_switch_domain_altp2m_by_id(d, a.u.view.view);
break;
case HVMOP_altp2m_set_mem_access:
diff --git a/xen/include/asm-arm/altp2m.h b/xen/include/asm-arm/altp2m.h
index 6074079..c2e44ab 100644
--- a/xen/include/asm-arm/altp2m.h
+++ b/xen/include/asm-arm/altp2m.h
@@ -52,6 +52,10 @@ void altp2m_vcpu_destroy(struct vcpu *v);
/* Get current alternate p2m table. */
struct p2m_domain *altp2m_get_altp2m(struct vcpu *v);
+/* Switch alternate p2m for entire domain */
+int altp2m_switch_domain_altp2m_by_id(struct domain *d,
+ unsigned int idx);
+
/* Make a specific alternate p2m valid. */
int altp2m_init_by_id(struct domain *d,
unsigned int idx);
Regards,
--
Julien Grall
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