Re: [PATCH RFC] powerpc: Implements MMIO emulation for lvx/stvx instructions
On Wed, Aug 30, 2017 at 07:45:17PM +1000, Paul Mackerras wrote:
> On Tue, Aug 29, 2017 at 07:18:01PM -0300, Jose Ricardo Ziviani wrote:
> > Hello!
> >
> > This patch implements MMIO emulation for two instructions: lvx and stvx. I
> > started to implement other instructions but I'd like to have this reviewed
> > beforehand because this is my first patch here and I'll certainly have some
> > rework/fixes :-).
> >
> > Note: stvx is only storing 8 bytes, for some reason the code
> > "vcpu->arch.paddr_accessed += run->mmio.len;", which adds the 8-byte offset
> > after the first write is not making any difference (interesting that it
> > works for load operations). I'm still investigating it but any idea about
> > it will be appreciated.
>
> The run structure is mmapped by userspace (i.e. QEMU) and can be
> written by userspace between the first and the second exits to
> userspace (you have to do two exits to userspace because you can only
> transfer 8 bytes on each exit). It's possible that userspace might be
> clearing run->mmio.len. In general it's better not to rely on
> anything in *run (except of course the mmio_data for a MMIO read) when
> we come in from userspace to the kernel.
>
> Paul.
>
Hello Paul,
My bad, actually it works. I was mmap'ping an address that doesn't allow
16-byte writing access. After mmap'ping a higher address (of the same device) I
was able to perform 16-byte read/write.
== before stvx ==
(gdb) info registers vr0
vr0 {uint128 = 0x12345678abcdef09, ...}
(gdb) info registers r9
r9 0x3fffb7c90010
(gdb) x /4wx 0x3fffb7c90010
0x3fffb7c90010: 0x 0x 0x 0x
(gdb) info registers r28
r28 0x0
stvxv0,r28,r9
== after stvx ==
(gdb) x /4wx 0x3fffb7c90010
0x3fffb7c90010: 0x12345678 0x 0xabcdef09 0x
== before lvx ==
(gdb) info registers vr10
vr10 {uint128 = 0x,...}
lvx v10,r28,r9
== after lvx ==
(gdb) info registers vr10
vr10 {uint128 = 0x12345678abcdef09,...}
If you think it's ok I'll submit this patch without the RFC.
Thank you very much!
Ziviani
Re: [PATCH RFC] powerpc: Implements MMIO emulation for lvx/stvx instructions
On Tue, Aug 29, 2017 at 07:18:01PM -0300, Jose Ricardo Ziviani wrote: > Hello! > > This patch implements MMIO emulation for two instructions: lvx and stvx. I > started to implement other instructions but I'd like to have this reviewed > beforehand because this is my first patch here and I'll certainly have some > rework/fixes :-). > > Note: stvx is only storing 8 bytes, for some reason the code > "vcpu->arch.paddr_accessed += run->mmio.len;", which adds the 8-byte offset > after the first write is not making any difference (interesting that it works > for load operations). I'm still investigating it but any idea about it will > be appreciated. The run structure is mmapped by userspace (i.e. QEMU) and can be written by userspace between the first and the second exits to userspace (you have to do two exits to userspace because you can only transfer 8 bytes on each exit). It's possible that userspace might be clearing run->mmio.len. In general it's better not to rely on anything in *run (except of course the mmio_data for a MMIO read) when we come in from userspace to the kernel. Paul.
[PATCH RFC] powerpc: Implements MMIO emulation for lvx/stvx instructions
Hello! This patch implements MMIO emulation for two instructions: lvx and stvx. I started to implement other instructions but I'd like to have this reviewed beforehand because this is my first patch here and I'll certainly have some rework/fixes :-). Note: stvx is only storing 8 bytes, for some reason the code "vcpu->arch.paddr_accessed += run->mmio.len;", which adds the 8-byte offset after the first write is not making any difference (interesting that it works for load operations). I'm still investigating it but any idea about it will be appreciated. Thank you very much, Jose Ricardo Ziviani (1): KVM: PPC: Book3S: Add MMIO emulation for VMX instructions arch/powerpc/include/asm/kvm_host.h | 2 + arch/powerpc/include/asm/kvm_ppc.h| 4 + arch/powerpc/include/asm/ppc-opcode.h | 6 ++ arch/powerpc/kvm/emulate_loadstore.c | 32 +++ arch/powerpc/kvm/powerpc.c| 162 ++ 5 files changed, 189 insertions(+), 17 deletions(-) -- 2.7.4
