On 3/9/23 05:59, Borislav Petkov wrote:
First of all,
thanks for proactively pointing that out instead of simply using what's
there and we get to find out later, only by chance.
Much appreciated. :-)
On Thu, Mar 09, 2023 at 11:12:10AM +0000, David Woodhouse wrote:
Right, I think we're ok with the following basic rules:
- pure arch/x86/ code should use the x86_platform function pointers to
query hypervisor capabilities/peculiarities
- cc_platform_has() should be used in generic/driver code as it
abstracts away the underlying platform better. IOW, querying
x86_platform.... in generic, platform-agnostic driver code looks weird to
say the least
The hope is that those two should be enough to support most guest types
and not let the zoo get too much out of hand...
Thx.
In
https://lore.kernel.org/all/20230308171328.1562857-13-usama.arif@xxxxxxxxxxxxx/
I added an sev_es_active() helper for x86 code.
Is that consistent with the vision here, or should I do something different?
So looking at sev_es_init_vc_handling() where we set that key, I'm
*thinking* that key can be removed now and the code should check
cc_platform_has(CC_ATTR_GUEST_STATE_ENCRYPT)
instead.
Because if some of the checks in that function below fail, the guest
will terminate anyway.
Jörg, Tom?
I believe Joerg added that key for performance reasons, since it is used
on the exception path and can avoid all the calls to cc_platform_has(). I
think that key should stay.
Maybe David can introduce an CC_ATTR_GUEST_SEV_ES attribute that returns
true if the guest is an ES or SNP guest. Or do we introduce a
CC_ATTR_PARALLEL_BOOT attribute that returns true for any SEV guest.
Then the "if cc_platform_has(CC_ATTR_GUEST_STATE_ENCRYPT) && !has_sev_es"
check in arch/x86/kernel/smpboot.c can be removed and the following check
can become if (x2apic_mode || cc_platform_has(CC_ATTR_PARALLEL_BOOT))
Not sure how that affects a TDX guest, though.
Thanks,
Tom
