On 07/02/2010 11:00 AM, Xiao Guangrong wrote:
The IOAPIC spec says:

When accessing these registers, accesses must be done one dword at a time.
For example, software should never access byte 2 from the Data register before
accessing bytes 0 and 1. The hardware will not attempt to recover from a bad
programming model in this case.

So, this patch removes other width access


The ioapic code also implements the ia64 iosapic. I'm guessing that does support 64-bit accesses. Please check the iosapic documentation.

There might be guests that use incorrect access despite the documentation; if real hardware supports it, it should work. So we need to start with just a warning, and allow the access. Later we can drop the invalid access.

@@ -288,6 +288,11 @@ static int ioapic_mmio_read(struct kvm_io_device *this, 
gpa_t addr, int len,
        ioapic_debug("addr %lx\n", (unsigned long)addr);
        ASSERT(!(addr&  0xf));      /* check alignment */

+       if (len != 4) {
+               printk(KERN_WARNING "ioapic: wrong length %d\n", len);
+               return 0;
+       }
+

Guest triggered, so needs to be rate limited.


--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.

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