Hi Sean,
On 10/14/2024 5:58 PM, Sean Christopherson wrote:
> On Thu, Sep 05, 2024, Pratik R. Sampat wrote:
>> From: Michael Roth <michael.roth@xxxxxxx>
>>
>> For SEV and SNP, currently __vm_phy_pages_alloc() handles setting the
>> region->protected_phy_pages bitmap to mark that the region needs to be
>> encrypted/measured into the initial guest state prior to
>
> Nothing needs to be measured, no? (because there's no attestation)
>
Right.
>> finalizing/starting the guest. It also marks what GPAs need to be mapped
>> as encrypted in the initial guest page table.
>
> ...
>
>> static inline void vm_mem_set_private(struct kvm_vm *vm, uint64_t gpa,
>> uint64_t size)
>> diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
>> index bbf90ad224da..d44a37aebcec 100644
>> --- a/tools/testing/selftests/kvm/lib/kvm_util.c
>> +++ b/tools/testing/selftests/kvm/lib/kvm_util.c
>> @@ -1991,6 +1991,43 @@ const char *exit_reason_str(unsigned int exit_reason)
>> return "Unknown";
>> }
>>
>> +/*
>> + * Set what guest GFNs need to be encrypted prior to finalizing a CoCo VM.
>> + *
>> + * Input Args:
>> + * vm - Virtual Machine
>> + * memslot - Memory region to allocate page from
>> + * paddr - Start of physical address to mark as encrypted
>> + * num - number of pages
>> + *
>> + * Output Args: None
>> + *
>> + * Return: None
>> + *
>> + * Generally __vm_phy_pages_alloc() will handle this automatically, but
>> + * for cases where the test handles managing the physical allocation and
>> + * mapping directly this interface should be used to mark physical pages
>> + * that are intended to be encrypted as part of the initial guest state.
>> + * This will also affect whether virt_map()/virt_pg_map() will map the
>> + * page as encrypted or not in the initial guest page table.
>> + *
>> + * If the initial guest state has already been finalized, then setting
>> + * it as encrypted will essentially be a noop since nothing more can be
>> + * encrypted into the initial guest state at that point.
>> + */
>> +void vm_mem_set_protected(struct kvm_vm *vm, uint32_t memslot,
>> + vm_paddr_t paddr, size_t num)
>> +{
>> + struct userspace_mem_region *region;
>> + sparsebit_idx_t pg, base;
>> +
>> + base = paddr >> vm->page_shift;
>> + region = memslot2region(vm, memslot);
>
> Please no, doing a memslot lookup in a helper like this is only going to encourage
> proliferation of bad code. vm_mem_add() really should be able to mark the region
> as protected.
>
> E.g. practically speaking, the only code that will be able to use this helper is
> code that is marking the entire memslot as protection. And ability to _clear_
> the protected_phy_pages bit is conspicuously missing.
>
