On 2016-05-30 07:45, Peter Xu wrote: > On Sun, May 29, 2016 at 11:21:35AM +0300, David Kiarie wrote: > [...] >>>> + >>>> +/* Programming format for MSI/MSI-X addresses */ >>>> +union VTD_IR_MSIAddress { >>>> + struct { >>>> + uint8_t __not_care:2; >>>> + uint8_t index_h:1; /* Interrupt index bit 15 */ >>>> + uint8_t sub_valid:1; /* SHV: Sub-Handle Valid bit */ >>>> + uint8_t int_mode:1; /* Interrupt format */ >>>> + uint16_t index_l:15; /* Interrupt index bit 14-0 */ >>>> + uint16_t __head:12; /* Should always be: 0x0fee */ >>>> + } QEMU_PACKED; >>>> + uint32_t data; >>>> +}; >>> >>> In a recent discussion, it was brought to my attention that you might >>> have a problem with bitfields when the host cpu is not x86. Have you >>> considered this ? >> >> In a case when say the host cpu is little endian. > > I assume you mean when host cpu is big endian. x86 was little endian, > and I was testing on x86. > > I think you are right. I should do conditional byte swap for all > uint{16/32/64} cases within the fields. For example, index_l field in > above VTD_IR_MSIAddress. And there are several other cases that need > special treatment in the patchset. Will go over and fix corresponding > issues in next version.
You actually need bit-swap with bit fields, see e.g. hw/net/vmxnet3.h. Jan
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