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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [PATCH] Re: [Xen-devel] [PATCH] Std VGA Performance
On Mon, 2007-10-29 at 19:17 +0000, Keir Fraser wrote:
>
> All that's changed for ia64 is the definition of the buffered ioreq
> structure, which has become more densely packed. All the rest of the
> acceleration is (currently) x86-specific. So this shouldn't be too hard to
> track down...
Yes, you're right, but easy to overlook, and I'm not sure how it
works on x86. I copied the x86 code for filling in the buffered ioreq,
but failed to notice that it attempts to store 4 bytes of data into a 2
byte field... The comment for the size entry in buf_ioreq could be
interpreted that only 1, 2, and 8 bytes are expected, but I definitely
see 4 bytes on occasion. I'd guess x86 has a bug here that's simply not
exposed because of the 16bit code that's probably being used to
initialize VGA. I also question the 8 byte support, which is why I
skipped it in the patch below. Wouldn't an 8 byte MMIO access that
isn't a timeoffset be possible? Keir, please apply this to the staging
tree. Thanks,
Alex
Signed-off-by: Alex Williamson <alex.williamson@xxxxxx>
--
diff -r 4034317507de xen/arch/ia64/vmx/mmio.c
--- a/xen/arch/ia64/vmx/mmio.c Mon Oct 29 16:49:02 2007 +0000
+++ b/xen/arch/ia64/vmx/mmio.c Tue Oct 30 10:03:42 2007 -0600
@@ -55,53 +55,68 @@ static int hvm_buffered_io_intercept(ior
static int hvm_buffered_io_intercept(ioreq_t *p)
{
struct vcpu *v = current;
- spinlock_t *buffered_io_lock;
- buffered_iopage_t *buffered_iopage =
+ buffered_iopage_t *pg =
(buffered_iopage_t *)(v->domain->arch.hvm_domain.buffered_io_va);
- unsigned long tmp_write_pointer = 0;
+ buf_ioreq_t bp;
int i;
+ /* Ensure buffered_iopage fits in a page */
+ BUILD_BUG_ON(sizeof(buffered_iopage_t) > PAGE_SIZE);
+
/* ignore READ ioreq_t! */
- if ( p->dir == IOREQ_READ )
- return 0;
-
- for ( i = 0; i < HVM_BUFFERED_IO_RANGE_NR; i++ ) {
- if ( p->addr >= hvm_buffered_io_ranges[i]->start_addr &&
- p->addr + p->size - 1 < hvm_buffered_io_ranges[i]->start_addr +
- hvm_buffered_io_ranges[i]->length )
+ if (p->dir == IOREQ_READ)
+ return 0;
+
+ for (i = 0; i < HVM_BUFFERED_IO_RANGE_NR; i++) {
+ if (p->addr >= hvm_buffered_io_ranges[i]->start_addr &&
+ p->addr + p->size - 1 < hvm_buffered_io_ranges[i]->start_addr +
+ hvm_buffered_io_ranges[i]->length)
break;
}
- if ( i == HVM_BUFFERED_IO_RANGE_NR )
- return 0;
-
- buffered_io_lock = &v->domain->arch.hvm_domain.buffered_io_lock;
- spin_lock(buffered_io_lock);
-
- if ( buffered_iopage->write_pointer - buffered_iopage->read_pointer ==
- (unsigned long)IOREQ_BUFFER_SLOT_NUM ) {
+ if (i == HVM_BUFFERED_IO_RANGE_NR)
+ return 0;
+
+ bp.type = p->type;
+ bp.dir = p->dir;
+ switch (p->size) {
+ case 1:
+ bp.size = 0;
+ break;
+ case 2:
+ bp.size = 1;
+ break;
+ default:
+ /* Could use quad word semantics, but it only appears
+ * to be useful for timeoffset data. */
+ return 0;
+ }
+ bp.data = (uint16_t)p->data;
+ bp.addr = (uint32_t)p->addr;
+
+ spin_lock(&v->domain->arch.hvm_domain.buffered_io_lock);
+
+ if (pg->write_pointer - pg->read_pointer == IOREQ_BUFFER_SLOT_NUM) {
/* the queue is full.
* send the iopacket through the normal path.
* NOTE: The arithimetic operation could handle the situation for
* write_pointer overflow.
*/
- spin_unlock(buffered_io_lock);
- return 0;
- }
-
- tmp_write_pointer = buffered_iopage->write_pointer % IOREQ_BUFFER_SLOT_NUM;
-
- memcpy(&buffered_iopage->ioreq[tmp_write_pointer], p, sizeof(ioreq_t));
-
- /*make the ioreq_t visible before write_pointer*/
+ spin_unlock(&v->domain->arch.hvm_domain.buffered_io_lock);
+ return 0;
+ }
+
+ memcpy(&pg->buf_ioreq[pg->write_pointer % IOREQ_BUFFER_SLOT_NUM],
+ &bp, sizeof(bp));
+
+ /* Make the ioreq_t visible before write_pointer */
wmb();
- buffered_iopage->write_pointer++;
-
- spin_unlock(buffered_io_lock);
+ pg->write_pointer++;
+
+ spin_unlock(&v->domain->arch.hvm_domain.buffered_io_lock);
return 1;
}
-
static void low_mmio_access(VCPU *vcpu, u64 pa, u64 *val, size_t s, int dir)
{
@@ -110,32 +125,36 @@ static void low_mmio_access(VCPU *vcpu,
ioreq_t *p;
vio = get_vio(v->domain, v->vcpu_id);
- if (vio == 0) {
- panic_domain(NULL,"bad shared page: %lx", (unsigned long)vio);
- }
+ if (!vio)
+ panic_domain(NULL, "bad shared page");
+
p = &vio->vp_ioreq;
+
p->addr = pa;
p->size = s;
p->count = 1;
+ if (dir == IOREQ_WRITE)
+ p->data = *val;
+ else
+ p->data = 0;
+ p->data_is_ptr = 0;
p->dir = dir;
- if (dir==IOREQ_WRITE) // write;
- p->data = *val;
- else if (dir == IOREQ_READ)
- p->data = 0; // clear all bits
- p->data_is_ptr = 0;
+ p->df = 0;
p->type = 1;
- p->df = 0;
p->io_count++;
+
if (hvm_buffered_io_intercept(p)) {
p->state = STATE_IORESP_READY;
vmx_io_assist(v);
- return;
- } else
- vmx_send_assist_req(v);
- if (dir == IOREQ_READ) { // read
+ if (dir != IOREQ_READ)
+ return;
+ }
+
+ vmx_send_assist_req(v);
+ if (dir == IOREQ_READ)
*val = p->data;
- }
+
return;
}
@@ -227,16 +246,18 @@ static void legacy_io_access(VCPU *vcpu,
ioreq_t *p;
vio = get_vio(v->domain, v->vcpu_id);
- if (vio == 0) {
- panic_domain(NULL,"bad shared page\n");
- }
+ if (!vio)
+ panic_domain(NULL, "bad shared page\n");
+
p = &vio->vp_ioreq;
- p->addr = TO_LEGACY_IO(pa&0x3ffffffUL);
+ p->addr = TO_LEGACY_IO(pa & 0x3ffffffUL);
p->size = s;
p->count = 1;
p->dir = dir;
- if (dir == IOREQ_WRITE) // write;
+ if (dir == IOREQ_WRITE)
p->data = *val;
+ else
+ p->data = 0;
p->data_is_ptr = 0;
p->type = 0;
p->df = 0;
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