On Thu, Jun 22, 2023 at 04:16:29PM -0700, isaku.yamahata@xxxxxxxxx wrote:
> From: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
>
> Add flags to strut kvm_gfn_range to indicate who triggered the callback
> and new memory attributes.
>
> TDX needs to know the reason for a callback by kvm_unmap_gfn_range(). mmu
> notifier, set memory attributes ioctl or KVM gmem callback. With TDX,
> zapping a private page from the encrypted page table and adding the page
> back to the same private GPA results in zeroing the page, and the guest has
> to accept the page again. On the change of memory attribute from private
> to shared, zapping the GPA range irrespective to private-or-shared and
> expecting the fault doesn't work for TDX. Instead, zap shared pages only
> and keep the private pages. Concretely
> - If it's from mmu notifier, zap shared pages.
> - If it's from KVM gmem, zap private pages.
> - If setting memory attributes to private, zap shared pages.
> - If setting memory attributes to shared, zap private pages.
>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
>
> ---
> Changes v1 -> v2:
> - consolidate KVM_GFN_RANGE_FLAGS_GMEM_{PUNCH_HOLE, RELEASE} into
> KVM_GFN_RANGE_FLAGS_GMEM.
> - Update the commit message to describe TDX more. Drop SEV_SNP.
> ---
> include/linux/kvm_host.h | 10 +++++++++-
> virt/kvm/guest_mem.c | 9 ++++++---
> virt/kvm/kvm_main.c | 4 +++-
> 3 files changed, 18 insertions(+), 5 deletions(-)
>
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 1a47cedae8a1..1fe0516fcddf 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -256,12 +256,20 @@ int kvm_async_pf_wakeup_all(struct kvm_vcpu *vcpu);
> #endif
>
> #ifdef CONFIG_KVM_GENERIC_MMU_NOTIFIER
> +
> +#define KVM_GFN_RANGE_FLAGS_SET_MEM_ATTR BIT(0)
> +#define KVM_GFN_RANGE_FLAGS_GMEM BIT(1)
> +
> struct kvm_gfn_range {
> struct kvm_memory_slot *slot;
> gfn_t start;
> gfn_t end;
> - pte_t pte;
> + union {
> + pte_t pte;
> + u64 attrs;
> + };
> bool may_block;
> + unsigned int flags;
> };
> bool kvm_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range);
> bool kvm_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range);
> diff --git a/virt/kvm/guest_mem.c b/virt/kvm/guest_mem.c
> index cdf2d84683c8..387226136960 100644
> --- a/virt/kvm/guest_mem.c
> +++ b/virt/kvm/guest_mem.c
> @@ -99,7 +99,8 @@ static struct folio *kvm_gmem_get_folio(struct file *file, pgoff_t index)
> }
>
> static void kvm_gmem_invalidate_begin(struct kvm *kvm, struct kvm_gmem *gmem,
> - pgoff_t start, pgoff_t end)
> + pgoff_t start, pgoff_t end,
> + unsigned int flags)
> {
> struct kvm_memory_slot *slot;
> unsigned long index;
> @@ -118,6 +119,7 @@ static void kvm_gmem_invalidate_begin(struct kvm *kvm, struct kvm_gmem *gmem,
> .slot = slot,
> .pte = __pte(0),
> .may_block = true,
> + .flags = flags,
> };
>
> kvm_mmu_invalidate_range_add(kvm, gfn_range.start, gfn_range.end);
> @@ -156,7 +158,8 @@ static long kvm_gmem_punch_hole(struct file *file, loff_t offset, loff_t len)
> */
> filemap_invalidate_lock(file->f_mapping);
>
> - kvm_gmem_invalidate_begin(kvm, gmem, start, end);
> + kvm_gmem_invalidate_begin(kvm, gmem, start, end,
> + KVM_GFN_RANGE_FLAGS_GMEM);
Do you anticipate ever needing to pass a different flag via
kvm_gmem_invalidate_begin()? If not it might make sense to just
hard-code it rather than passing as a parameter.
-Mike
