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Re: [Xen-devel] [PATCH v8 14/27] ARM: vITS: introduce translation table walks
On 12/04/17 14:36, Andre Przywara wrote:
Hi,
On 12/04/17 14:22, Julien Grall wrote:
On 12/04/17 01:44, Andre Przywara wrote:
The ITS stores the target (v)CPU and the (virtual) LPI number in tables.
Introduce functions to walk those tables and translate an device ID -
event ID pair into a pair of virtual LPI and vCPU.
We map those tables on demand - which is cheap on arm64 - and copy the
respective entries before using them, to avoid the guest tampering with
them meanwhile.
To allow compiling without warnings, we declare two functions as
non-static for the moment, which two later patches will fix.
Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx>
---
xen/arch/arm/vgic-v3-its.c | 183
+++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 183 insertions(+)
diff --git a/xen/arch/arm/vgic-v3-its.c b/xen/arch/arm/vgic-v3-its.c
index a60f9b2..632ab84 100644
--- a/xen/arch/arm/vgic-v3-its.c
+++ b/xen/arch/arm/vgic-v3-its.c
@@ -78,6 +78,7 @@ struct vits_itte
uint16_t pad;
};
+#define UNMAPPED_COLLECTION ((uint16_t)~0)
On v5 (patch #28), I asked to minimize the use of uint16_t (resp.
uint64_t) when it refers to collection (resp. ITTE). But it sounds like
you missed again that point.
Well, I introduced that below, just failed to use it *everywhere*.
...
#define GITS_BASER_RO_MASK (GITS_BASER_TYPE_MASK | \
(31UL << GITS_BASER_ENTRY_SIZE_SHIFT))
@@ -94,6 +95,188 @@ void vgic_v3_its_free_domain(struct domain *d)
ASSERT(RB_EMPTY_ROOT(&d->arch.vgic.its_devices));
}
+/*
+ * The physical address is encoded slightly differently depending on
+ * the used page size: the highest four bits are stored in the lowest
+ * four bits of the field for 64K pages.
+ */
+static paddr_t get_baser_phys_addr(uint64_t reg)
+{
+ if ( reg & BIT(9) )
+ return (reg & GENMASK(47, 16)) |
+ ((reg & GENMASK(15, 12)) << 36);
+ else
+ return reg & GENMASK(47, 12);
+}
+
+/*
+ * Our collection table encoding:
+ * Just contains the 16-bit VCPU ID of the respective vCPU.
+ */
+#define COLL_TABLE_ENTRY_SIZE 2UL
... (here)
+
+/* Must be called with the ITS lock held. */
+static struct vcpu *get_vcpu_from_collection(struct virt_its *its,
+ uint16_t collid)
+{
+ paddr_t addr = get_baser_phys_addr(its->baser_coll);
+ uint16_t vcpu_id;
I don't see any BUILD_BUG_ON making sure you can store a vCPU ID in
uint16_t.
+ int ret;
+
+ ASSERT(spin_is_locked(&its->its_lock));
+
+ if ( collid >= its->max_collections )
+ return NULL;
+
+ ret = vgic_access_guest_memory(its->d, addr + collid *
sizeof(uint16_t),
+ &vcpu_id, sizeof(vcpu_id), false);
Minimizing the use of uint16_t will likely make this code less confusing
to read as it mixes sizeof(vcpu_id) and sizeof(uint16_t).
The idea here is to use the actual type of the variable used instead of
putting an explicit type in here, since this can get out of sync.
So would a typedef meet your expectations?
typedef uint16_t coll_table_entry_t;
typedef uint64_t dev_table_entry_t;
And then use that throughout the code?
Yes please.
Cheers,
--
Julien Grall
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