Re: [PATCH 1/4] x86/hyperv: Add missing ARCH_HAS_CC_PLATFORM dependency

[Tianyu Lan]

On 2/23/2022 4:08 AM, Borislav Petkov wrote:
> On Tue, Feb 22, 2022 at 09:57:37PM +0300, Kirill A. Shutemov wrote:
> > On x86, cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT) supposes to return
> > true for HyperV if isolation is supported. But it only does it if the
> > kernel is compiled with AMD_MEM_ENCRYPT enabled.
> >
> > It happens due to missed ARCH_HAS_CC_PLATFORM dependency. Without
> > ARCH_HAS_CC_PLATFORM enabled, cc_platform_has() always returns false.
> >
> > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
> > Cc: "K. Y. Srinivasan" <kys@xxxxxxxxxxxxx>
> > Cc: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>
> > Cc: Stephen Hemminger <sthemmin@xxxxxxxxxxxxx>
> > Cc: Wei Liu <wei.liu@xxxxxxxxxx>
> > Cc: Dexuan Cui <decui@xxxxxxxxxxxxx>
> > Cc: Tianyu Lan <Tianyu.Lan@xxxxxxxxxxxxx>
> > ---
> >   drivers/hv/Kconfig | 1 +
> >   1 file changed, 1 insertion(+)
> >
> > diff --git a/drivers/hv/Kconfig b/drivers/hv/Kconfig
> > index 0747a8f1fcee..424d3f0751dc 100644
> > --- a/drivers/hv/Kconfig
> > +++ b/drivers/hv/Kconfig
> > @@ -8,6 +8,7 @@ config HYPERV
> >   		|| (ARM64 && !CPU_BIG_ENDIAN))
> >   	select PARAVIRT
> >   	select X86_HV_CALLBACK_VECTOR if X86
> > +	select ARCH_HAS_CC_PLATFORM if x86
> >   	select VMAP_PFN
> >   	help
> >   	  Select this option to run Linux as a Hyper-V client operating
> > --
>
> Good catch.
>
> I'm guessing this needs
>
> Fixes: c789b90a6904 ("x86/hyper-v: Add hyperv Isolation VM check in the cc_platform_has()")
>
> which added hyperv_cc_platform_has() and which needs to go to Linus now,
> as an urgent fix for 5.17 as that patch came into 5.17-rc1.
>
> Wei?

Hi Borias, wei and Kill:
      Current Hyper-V Isolation VM requires AMD_MEM_ENCRYPT option 
which selects ARCH_HAS_CC_PLATFORM. Linux guest can't boot up without 
AMD_MEM_ENCRYPT option. So this is why not select ARCH_HAS_CC_PLATFORM
here.