David Hildenbrand <david@xxxxxxxxxx> writes:
> On 13.05.25 18:34, Fuad Tabba wrote:
>> From: Ackerley Tng <ackerleytng@xxxxxxxxxx>
>>
>> This patch adds kvm_gmem_max_mapping_level(), which always returns
>> PG_LEVEL_4K since guest_memfd only supports 4K pages for now.
>>
>> When guest_memfd supports shared memory, max_mapping_level (especially
>> when recovering huge pages - see call to __kvm_mmu_max_mapping_level()
>> from recover_huge_pages_range()) should take input from
>> guest_memfd.
>>
>> Input from guest_memfd should be taken in these cases:
>>
>> + if the memslot supports shared memory (guest_memfd is used for
>> shared memory, or in future both shared and private memory) or
>> + if the memslot is only used for private memory and that gfn is
>> private.
>>
>> If the memslot doesn't use guest_memfd, figure out the
>> max_mapping_level using the host page tables like before.
>>
>> This patch also refactors and inlines the other call to
>> __kvm_mmu_max_mapping_level().
>>
>> In kvm_mmu_hugepage_adjust(), guest_memfd's input is already
>> provided (if applicable) in fault->max_level. Hence, there is no need
>> to query guest_memfd.
>>
>> lpage_info is queried like before, and then if the fault is not from
>> guest_memfd, adjust fault->req_level based on input from host page
>> tables.
>>
>> Signed-off-by: Ackerley Tng <ackerleytng@xxxxxxxxxx>
>> Signed-off-by: Fuad Tabba <tabba@xxxxxxxxxx>
>> ---
>> arch/x86/kvm/mmu/mmu.c | 92 ++++++++++++++++++++++++++--------------
>> include/linux/kvm_host.h | 7 +++
>> virt/kvm/guest_memfd.c | 12 ++++++
>> 3 files changed, 79 insertions(+), 32 deletions(-)
>>
>> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
>> index cfbb471f7c70..9e0bc8114859 100644
>> --- a/arch/x86/kvm/mmu/mmu.c
>> +++ b/arch/x86/kvm/mmu/mmu.c
>> @@ -3256,12 +3256,11 @@ static int host_pfn_mapping_level(struct kvm *kvm, gfn_t gfn,
>> return level;
>> }
> [...]
>
>> static u8 kvm_max_level_for_fault_and_order(struct kvm *kvm,
>> struct kvm_page_fault *fault,
>> int order)
>> @@ -4523,7 +4551,7 @@ static int __kvm_mmu_faultin_pfn(struct kvm_vcpu *vcpu,
>> {
>> unsigned int foll = fault->write ? FOLL_WRITE : 0;
>>
>> - if (fault->is_private || kvm_gmem_memslot_supports_shared(fault->slot))
>> + if (fault_from_gmem(fault))
>
> Should this change rather have been done in the previous patch?
>
> (then only adjust fault_from_gmem() in this function as required)
>
Yes, that is a good idea, thanks!
>> return kvm_mmu_faultin_pfn_gmem(vcpu, fault);
>>
>> foll |= FOLL_NOWAIT;
>> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
>> index de7b46ee1762..f9bb025327c3 100644
>> --- a/include/linux/kvm_host.h
>> +++ b/include/linux/kvm_host.h
>> @@ -2560,6 +2560,7 @@ static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn)
>> int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot,
>> gfn_t gfn, kvm_pfn_t *pfn, struct page **page,
>> int *max_order);
>> +int kvm_gmem_mapping_order(const struct kvm_memory_slot *slot, gfn_t gfn);
>> #else
>> static inline int kvm_gmem_get_pfn(struct kvm *kvm,
>> struct kvm_memory_slot *slot, gfn_t gfn,
>> @@ -2569,6 +2570,12 @@ static inline int kvm_gmem_get_pfn(struct kvm *kvm,
>> KVM_BUG_ON(1, kvm);
>> return -EIO;
>> }
>> +static inline int kvm_gmem_mapping_order(const struct kvm_memory_slot *slot,
>> + gfn_t gfn)
>
> Probably should indent with two tabs here.
Yup!
