On Fri, May 02, 2025 at 04:08:25PM +0300, Kirill A. Shutemov wrote:
>Preallocate a page to be used in the link_external_spt() and
>set_external_spte() paths.
>
>In the worst-case scenario, handling a page fault might require a
>tdx_nr_pamt_pages() pages for each page table level.
>
>Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
>---
> arch/x86/include/asm/kvm_host.h | 2 ++
> arch/x86/kvm/mmu/mmu.c | 10 ++++++++++
> 2 files changed, 12 insertions(+)
>
>diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
>index 91958c55f918..a5661499a176 100644
>--- a/arch/x86/include/asm/kvm_host.h
>+++ b/arch/x86/include/asm/kvm_host.h
>@@ -849,6 +849,8 @@ struct kvm_vcpu_arch {
> */
> struct kvm_mmu_memory_cache mmu_external_spt_cache;
>
>+ struct kvm_mmu_memory_cache pamt_page_cache;
>+
> /*
> * QEMU userspace and the guest each have their own FPU state.
> * In vcpu_run, we switch between the user and guest FPU contexts.
>diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
>index a284dce227a0..7bfa0dc50440 100644
>--- a/arch/x86/kvm/mmu/mmu.c
>+++ b/arch/x86/kvm/mmu/mmu.c
>@@ -616,6 +616,15 @@ static int mmu_topup_memory_caches(struct kvm_vcpu *vcpu, bool maybe_indirect)
> if (r)
> return r;
> }
>+
>+ if (vcpu->kvm->arch.vm_type == KVM_X86_TDX_VM) {
The check for vcpu->kvm->arch.vm_type == KVM_X86_TDX_VM is identical to
kvm_has_mirrored_tdp() a few lines above.
>+ int nr = tdx_nr_pamt_pages(tdx_get_sysinfo());
Since you're already accessing tdx_sysinfo, you can check if dynamic PAMT is
enabled and allocate the pamt page cache accordingly.
>+ r = kvm_mmu_topup_memory_cache(&vcpu->arch.pamt_page_cache,
>+ nr * PT64_ROOT_MAX_LEVEL);
>+ if (r)
>+ return r;
>+ }
>+
> return kvm_mmu_topup_memory_cache(&vcpu->arch.mmu_page_header_cache,
> PT64_ROOT_MAX_LEVEL);
> }
>@@ -626,6 +635,7 @@ static void mmu_free_memory_caches(struct kvm_vcpu *vcpu)
> kvm_mmu_free_memory_cache(&vcpu->arch.mmu_shadow_page_cache);
> kvm_mmu_free_memory_cache(&vcpu->arch.mmu_shadowed_info_cache);
> kvm_mmu_free_memory_cache(&vcpu->arch.mmu_external_spt_cache);
>+ kvm_mmu_free_memory_cache(&vcpu->arch.pamt_page_cache);
> kvm_mmu_free_memory_cache(&vcpu->arch.mmu_page_header_cache);
> }
>
>--
>2.47.2
>
