An error about virtual bar write in pci virtualization

[liulog]

I experiment pci virtualization on qemu-system-riscv64.

But I found zone1 can't boot successfully, because page-fault in mem64 region.

It means 0x4_0000_0000 region isn't mapped in zone1 memoryset.

Then, I find 00:02.0 (virtio-blk-pci device) 's Memory is wrong, becasue there should be one memory region in 0x4_0000_0000 instead 0x4000_0000.

After a period of investigation, I find zone0 read error bar4 related to 00:02.0. So I deep in code. There exists an error. Mmio bar4 read correct value but read bar4 returns an error value.

And I find the first read is ok. But later reads after first write are wrong. The low 4bits is missing which are read-only. This is a serious error.

I try to use the following code to fix it, it now works ok.

I use two virtio-blk-pci devices. Now zone0 and zone1 can work.

@ZhongkaiXu @dallasxy Please check it.

[ZhongkaiXu]

Thanks for pointing it out, there is definitely an issue here and your fix makes sense, you can use it for now. Our new vpci is on the way.