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[Qemu-devel] [PATCH comment tweaked] msix: allow byte and word reading f
From: |
mst |
Subject: |
[Qemu-devel] [PATCH comment tweaked] msix: allow byte and word reading from mmio |
Date: |
Tue, 16 Nov 2010 15:14:53 +0200 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
Although explicitly disallowed by the PCI spec, some guests read a
single byte or word from mmio. Likely a guest OS bug, but I have an OS
which reads single bytes and it works fine on real hardware.
Signed-off-by: Bernhard Kohl <address@hidden>
Signed-off-by: Michael S. Tsirkin <address@hidden>
---
OK so it could like something like the below. However, my question is:
do we need to put this in or can the guest simply be fixed?
hw/msix.c | 31 +++++++++++++++++++++++++++----
1 files changed, 27 insertions(+), 4 deletions(-)
diff --git a/hw/msix.c b/hw/msix.c
index f66d255..38dff59 100644
--- a/hw/msix.c
+++ b/hw/msix.c
@@ -102,10 +102,28 @@ static uint32_t msix_mmio_readl(void *opaque,
target_phys_addr_t addr)
return pci_get_long(page + offset);
}
-static uint32_t msix_mmio_read_unallowed(void *opaque, target_phys_addr_t addr)
+ /* Note:
+ * PCI spec requires that all MSI-X table accesses are either DWORD or QWORD,
+ * size aligned. Some guests seem to violate this rule for read accesses,
+ * performing single byte reads. Since it's easy to support this, let's do
so.
+ * Also support 16 bit size aligned reads, just in case.
+ */
+static uint32_t msix_mmio_readw(void *opaque, target_phys_addr_t addr)
{
- fprintf(stderr, "MSI-X: only dword read is allowed!\n");
- return 0;
+ PCIDevice *dev = opaque;
+ unsigned int offset = addr & (MSIX_PAGE_SIZE - 1) & ~0x1;
+ void *page = dev->msix_table_page;
+
+ return pci_get_word(page + offset);
+}
+
+static uint32_t msix_mmio_readb(void *opaque, target_phys_addr_t addr)
+{
+ PCIDevice *dev = opaque;
+ unsigned int offset = addr & (MSIX_PAGE_SIZE - 1);
+ void *page = dev->msix_table_page;
+
+ return pci_get_byte(page + offset);
}
static uint8_t msix_pending_mask(int vector)
@@ -192,6 +210,11 @@ static void msix_mmio_writel(void *opaque,
target_phys_addr_t addr,
msix_handle_mask_update(dev, vector);
}
+/* PCI spec:
+ * For all accesses to MSI-X Table and MSI-X PBA fields, software must use
+ * aligned full DWORD or aligned full QWORD transactions; otherwise, the result
+ * is undefined.
+ */
static void msix_mmio_write_unallowed(void *opaque, target_phys_addr_t addr,
uint32_t val)
{
@@ -203,7 +226,7 @@ static CPUWriteMemoryFunc * const msix_mmio_write[] = {
};
static CPUReadMemoryFunc * const msix_mmio_read[] = {
- msix_mmio_read_unallowed, msix_mmio_read_unallowed, msix_mmio_readl
+ msix_mmio_readb, msix_mmio_readw, msix_mmio_readl
};
/* Should be called from device's map method. */
--
1.7.3.2.91.g446ac