75 lines
2.7 KiB
Diff
75 lines
2.7 KiB
Diff
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# HG changeset patch
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# User kfraser@localhost.localdomain
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# Date 1181157846 -3600
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# Node ID 677731eb734d8d7afa37a2e31ca2ed85fbebc2a5
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# Parent f5a71c9771a81f220926ac11e4c9a2a27530c20a
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[HVM] Prevent usb driver crashes in Windows
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Use atomic updates to read/write usb controller data.
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This can be done because:
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a) word copies on x86 are atomic
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b) The USB spec requires word alignment
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This will need to be enhanced once USB 1.2 is supported.
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Signed-off-by: Steve Ofsthun <sofsthun@virtualiron.com>
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Update to copy 'longword'-sized atoms.
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Signed-off-by: Keir Fraser <keir@xensource.com>
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Index: xen-3.1-testing/tools/ioemu/target-i386-dm/exec-dm.c
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===================================================================
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--- xen-3.1-testing.orig/tools/ioemu/target-i386-dm/exec-dm.c
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+++ xen-3.1-testing/tools/ioemu/target-i386-dm/exec-dm.c
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@@ -434,6 +434,31 @@ int iomem_index(target_phys_addr_t addr)
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extern unsigned long *logdirty_bitmap;
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extern unsigned long logdirty_bitmap_size;
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+/*
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+ * Replace the standard byte memcpy with a word memcpy for appropriately sized
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+ * memory copy operations. Some users (USB-UHCI) can not tolerate the possible
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+ * word tearing that can result from a guest concurrently writing a memory
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+ * structure while the qemu device model is modifying the same location.
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+ * Forcing a word-sized read/write prevents the guest from seeing a partially
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+ * written word-sized atom.
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+ */
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+void memcpy_words(void *dst, void *src, size_t n)
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+{
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+ while (n >= sizeof(long)) {
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+ *((long *)dst)++ = *((long *)src)++;
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+ n -= sizeof(long);
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+ }
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+
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+ if (n & 4)
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+ *((uint32_t *)dst)++ = *((uint32_t *)src)++;
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+
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+ if (n & 2)
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+ *((uint16_t *)dst)++ = *((uint16_t *)src)++;
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+
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+ if (n & 1)
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+ *((uint8_t *)dst)++ = *((uint8_t *)src)++;
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+}
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+
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void cpu_physical_memory_rw(target_phys_addr_t addr, uint8_t *buf,
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int len, int is_write)
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{
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@@ -470,7 +495,7 @@ void cpu_physical_memory_rw(target_phys_
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}
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} else if ((ptr = phys_ram_addr(addr)) != NULL) {
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/* Writing to RAM */
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- memcpy(ptr, buf, l);
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+ memcpy_words(ptr, buf, l);
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if (logdirty_bitmap != NULL) {
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/* Record that we have dirtied this frame */
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unsigned long pfn = addr >> TARGET_PAGE_BITS;
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@@ -506,7 +531,7 @@ void cpu_physical_memory_rw(target_phys_
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}
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} else if ((ptr = phys_ram_addr(addr)) != NULL) {
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/* Reading from RAM */
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- memcpy(buf, ptr, l);
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+ memcpy_words(buf, ptr, l);
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} else {
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/* Neither RAM nor known MMIO space */
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memset(buf, 0xff, len);
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