On 28/11/12 13:09, Will Deacon wrote:

On Sat, Nov 10, 2012 at 03:44:44PM +0000, Christoffer Dall wrote:

quoted

From: Marc Zyngier <redacted>

Wire the initial in-kernel MMIO support code for the VGIC, used
for the distributor emulation.

[...]

quoted

diff --git a/arch/arm/kvm/vgic.c b/arch/arm/kvm/vgic.c
new file mode 100644
index 0000000..26ada3b
--- /dev/null
+++ b/arch/arm/kvm/vgic.c

@@ -0,0 +1,138 @@
+/*
+ * Copyright (C) 2012 ARM Ltd.
+ * Author: Marc Zyngier <marc.zyngier@arm.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+
+#include <linux/kvm.h>
+#include <linux/kvm_host.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <asm/kvm_emulate.h>
+
+#define ACCESS_READ_VALUE	(1 << 0)
+#define ACCESS_READ_RAZ		(0 << 0)
+#define ACCESS_READ_MASK(x)	((x) & (1 << 0))
+#define ACCESS_WRITE_IGNORED	(0 << 1)
+#define ACCESS_WRITE_SETBIT	(1 << 1)
+#define ACCESS_WRITE_CLEARBIT	(2 << 1)
+#define ACCESS_WRITE_VALUE	(3 << 1)
+#define ACCESS_WRITE_MASK(x)	((x) & (3 << 1))
+
+/**
+ * vgic_reg_access - access vgic register
+ * @mmio:   pointer to the data describing the mmio access
+ * @reg:    pointer to the virtual backing of the vgic distributor struct
+ * @offset: least significant 2 bits used for word offset
+ * @mode:   ACCESS_ mode (see defines above)
+ *
+ * Helper to make vgic register access easier using one of the access
+ * modes defined for vgic register access
+ * (read,raz,write-ignored,setbit,clearbit,write)
+ */
+static void vgic_reg_access(struct kvm_exit_mmio *mmio, u32 *reg,
+			    u32 offset, int mode)
+{
+	int word_offset = offset & 3;

You can get rid of this variable.

quoted

+	int shift = word_offset * 8;

shift = (offset & 3) << 3;

quoted

+	u32 mask;
+	u32 regval;
+
+	/*
+	 * Any alignment fault should have been delivered to the guest
+	 * directly (ARM ARM B3.12.7 "Prioritization of aborts").
+	 */
+
+	mask = (~0U) >> (word_offset * 8);

then use shift here.

Sure.

quoted

+	if (reg)
+		regval = *reg;
+	else {

Use braces for the if clause.

Indeed.

quoted

+		BUG_ON(mode != (ACCESS_READ_RAZ | ACCESS_WRITE_IGNORED));
+		regval = 0;
+	}
+
+	if (mmio->is_write) {
+		u32 data = (*((u32 *)mmio->data) & mask) << shift;
+		switch (ACCESS_WRITE_MASK(mode)) {
+		case ACCESS_WRITE_IGNORED:
+			return;
+
+		case ACCESS_WRITE_SETBIT:
+			regval |= data;
+			break;
+
+		case ACCESS_WRITE_CLEARBIT:
+			regval &= ~data;
+			break;
+
+		case ACCESS_WRITE_VALUE:
+			regval = (regval & ~(mask << shift)) | data;
+			break;
+		}
+		*reg = regval;
+	} else {
+		switch (ACCESS_READ_MASK(mode)) {
+		case ACCESS_READ_RAZ:
+			regval = 0;
+			/* fall through */
+
+		case ACCESS_READ_VALUE:
+			*((u32 *)mmio->data) = (regval >> shift) & mask;
+		}
+	}
+}

It might be a good idea to have some port accessors for mmio->data otherwise
you'll likely get endianness issues creeping in.

Aarrgh! This depends on the relative endianess of host and guest. 'm
feeling slightly sick...

quoted

+/* All this should be handled by kvm_bus_io_*()... FIXME!!! */

I don't follow this comment :) Can you either make it clearer (and less
alarming!) or just drop it please?

The non-alarming version should read:

/*
 * I would have liked to use the kvm_bus_io_*() API instead, but
 * it cannot cope with banked registers (only the VM pointer is
 * passed around, and we need the vcpu). One of these days, someone
 * please fix it!
 */

quoted

+struct mmio_range {
+	unsigned long base;
+	unsigned long len;
+	bool (*handle_mmio)(struct kvm_vcpu *vcpu, struct kvm_exit_mmio *mmio,
+			    u32 offset);
+};

Why not make offset a phys_addr_t?

Very good point.

quoted

+static const struct mmio_range vgic_ranges[] = {
+	{}
+};
+
+static const
+struct mmio_range *find_matching_range(const struct mmio_range *ranges,
+				       struct kvm_exit_mmio *mmio,
+				       unsigned long base)
+{
+	const struct mmio_range *r = ranges;
+	unsigned long addr = mmio->phys_addr - base;

Same here, I don't think we want to truncate everything to unsigned long.

Indeed.

quoted

+	while (r->len) {
+		if (addr >= r->base &&
+		    (addr + mmio->len) <= (r->base + r->len))
+			return r;
+		r++;
+	}

Hmm, does this work correctly for adjacent mmio devices where addr sits
on the boundary (i.e. the first address of the second device)?

I think it is OK. We basically check that both ends of the access are
within a single range (we do not bother with cross range accesses).

	M.
-- 
Jazz is not dead. It just smells funny...