Re: [PATCH v6 07/11] hvf: Add Apple Silicon support

[Alexander Graf]

On 10.02.21 23:39, Peter Maydell wrote:
> On Wed, 10 Feb 2021 at 22:21, Alexander Graf <agraf@csgraf.de> wrote:
> > On 28.01.21 16:52, Peter Maydell wrote:
> > > On Wed, 20 Jan 2021 at 22:44, Alexander Graf <agraf@csgraf.de> wrote:
> > > > +            break;
> > > > +        case EC_AA64_SMC:
> > > > +            cpu_synchronize_state(cpu);
> > > > +            if (arm_is_psci_call(arm_cpu, EXCP_SMC)) {
> > > > +                arm_handle_psci_call(arm_cpu);
> > > Have you checked that all the PSCI code really can cope
> > > with being called from a non-TCG accelerator? (As an example
> > > the CPU_SUSPEND implementation calls the TCG wfi helper...)
> >
> > I have not explicitly tried it, but I don't see why the TCG
> > implementation of wfi should in principle break with hvf.
> Because the TCG implementation of wfi is "set some state fields
> and then longjump out to the TCG exec_cpu code-execution loop",
> and hvf doesn't use that loop.


I can confirm that it breaks, but are you really sure about the longjmp 
not working?

What would you prefer instead? Duplicate the PSCI implementation for HVF?


> > > > +            } else {
> > > > +                DPRINTF("unknown SMC! %016llx", env->xregs[0]);
> > > > +                env->xregs[0] = -1;
> > > This should inject an UNDEF exception into the guest. (Compare
> > > the pre_smc helper in target/arm/op_helper.c for TCG.)
> >
> > That would break Windows, which is one of the main use cases for hvf
> > support in QEMU.
> Why is Windows making bogus SMC calls ?


Let me have a quick at my crystal ball ... mmmmmmhhhh ... it's a bit 
blurry unfortunately.

I really don't think I'm the right person to answer that question :). 
But the Windows loader does invoke weird SMC calls on boot:


BdsDxe: starting Boot0002 "UEFI QEMU NVMe Ctrl 1234 1" from 
PciRoot(0x0)/Pci(0x1,0x0)/NVMe(0x1,00-00-00-00-00-00-00-00)
ConvertPages: failed to find range 102000 - 102FFF
ConvertPages: range BCCE4000 - BCD05FFF covers multiple entries
ConvertPages: range BCCE0000 - BCCEAFFF covers multiple entries
hvf_unknown_smc unknown SMC! 00000000c3000001
SetUefiImageMemoryAttributes - 0x00000000BF500000 - 0x0000000000040000 
(0x0000000000000008)
SetUefiImageMemoryAttributes - 0x00000000BC190000 - 0x0000000000040000 
(0x0000000000000008)
SetUefiImageMemoryAttributes - 0x00000000BC140000 - 0x0000000000040000 
(0x0000000000000008)
SetUefiImageMemoryAttributes - 0x00000000BF4C0000 - 0x0000000000030000 
(0x0000000000000008)
SetUefiImageMemoryAttributes - 0x00000000BC0F0000 - 0x0000000000040000 
(0x0000000000000008)
SetUefiImageMemoryAttributes - 0x00000000BBCB0000 - 0x0000000000040000 
(0x0000000000000008)
SetUefiImageMemoryAttributes - 0x00000000BBB00000 - 0x0000000000030000 
(0x0000000000000008)
SetUefiImageMemoryAttributes - 0x00000000BBAC0000 - 0x0000000000030000 
(0x0000000000000008)
hvf_unknown_smc unknown SMC! 0000000084000000
hvf_unknown_smc unknown SMC! 000000008400000a
hvf_unknown_smc unknown SMC! 000000008400000a
hvf_unknown_smc unknown SMC! 000000008400000a
hvf_unknown_smc unknown SMC! 000000008400000a
hvf_unknown_smc unknown SMC! 000000008400000a
hvf_unknown_smc unknown SMC! 000000008400000a
hvf_unknown_smc unknown SMC! 000000008400000a
hvf_unknown_smc unknown SMC! 000000008400000a
hvf_unknown_smc unknown SMC! 000000008400000a
hvf_unknown_smc unknown SMC! 000000008400000a


Alex