[PATCH v3 20/25] KVM: TDX: Add macro to retry SEAMCALLs when forcing vCPUs out of guest
From: Sean Christopherson <seanjc@google.com>
Date: 2025-10-17 00:33:23
Also in:
kvm, kvm-riscv, kvmarm, linux-coco, linux-mips, linux-riscv, linuxppc-dev, lkml, loongarch
Subsystem:
kernel virtual machine for x86 (kvm/x86), the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Sean Christopherson, Paolo Bonzini, Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
Add a macro to handle kicking vCPUs out of the guest and retrying SEAMCALLs on -EBUSY instead of providing small helpers to be used by each SEAMCALL. Wrapping the SEAMCALLs in a macro makes it a little harder to tease out which SEAMCALL is being made, but significantly reduces the amount of copy+paste code and makes it all but impossible to leave an elevated wait_for_sept_zap. Signed-off-by: Sean Christopherson <seanjc@google.com> --- arch/x86/kvm/vmx/tdx.c | 72 ++++++++++++++---------------------------- 1 file changed, 23 insertions(+), 49 deletions(-)
diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
index f6782b0ffa98..2e2dab89c98f 100644
--- a/arch/x86/kvm/vmx/tdx.c
+++ b/arch/x86/kvm/vmx/tdx.c@@ -294,25 +294,24 @@ static inline void tdx_disassociate_vp(struct kvm_vcpu *vcpu) vcpu->cpu = -1; } -static void tdx_no_vcpus_enter_start(struct kvm *kvm) -{ - struct kvm_tdx *kvm_tdx = to_kvm_tdx(kvm); - - lockdep_assert_held_write(&kvm->mmu_lock); - - WRITE_ONCE(kvm_tdx->wait_for_sept_zap, true); - - kvm_make_all_cpus_request(kvm, KVM_REQ_OUTSIDE_GUEST_MODE); -} - -static void tdx_no_vcpus_enter_stop(struct kvm *kvm) -{ - struct kvm_tdx *kvm_tdx = to_kvm_tdx(kvm); - - lockdep_assert_held_write(&kvm->mmu_lock); - - WRITE_ONCE(kvm_tdx->wait_for_sept_zap, false); -} +#define tdh_do_no_vcpus(tdh_func, kvm, args...) \ +({ \ + struct kvm_tdx *__kvm_tdx = to_kvm_tdx(kvm); \ + u64 __err; \ + \ + lockdep_assert_held_write(&kvm->mmu_lock); \ + \ + __err = tdh_func(args); \ + if (unlikely(tdx_operand_busy(__err))) { \ + WRITE_ONCE(__kvm_tdx->wait_for_sept_zap, true); \ + kvm_make_all_cpus_request(kvm, KVM_REQ_OUTSIDE_GUEST_MODE); \ + \ + __err = tdh_func(args); \ + \ + WRITE_ONCE(__kvm_tdx->wait_for_sept_zap, false); \ + } \ + __err; \ +}) /* TDH.PHYMEM.PAGE.RECLAIM is allowed only when destroying the TD. */ static int __tdx_reclaim_page(struct page *page)
@@ -1711,14 +1710,7 @@ static void tdx_track(struct kvm *kvm) if (unlikely(kvm_tdx->state != TD_STATE_RUNNABLE)) return; - err = tdh_mem_track(&kvm_tdx->td); - if (unlikely(tdx_operand_busy(err))) { - /* After no vCPUs enter, the second retry is expected to succeed */ - tdx_no_vcpus_enter_start(kvm); - err = tdh_mem_track(&kvm_tdx->td); - tdx_no_vcpus_enter_stop(kvm); - } - + err = tdh_do_no_vcpus(tdh_mem_track, kvm, &kvm_tdx->td); TDX_BUG_ON(err, TDH_MEM_TRACK, kvm); kvm_make_all_cpus_request(kvm, KVM_REQ_OUTSIDE_GUEST_MODE);
@@ -1770,14 +1762,8 @@ static void tdx_sept_remove_private_spte(struct kvm *kvm, gfn_t gfn, if (KVM_BUG_ON(level != PG_LEVEL_4K, kvm)) return; - err = tdh_mem_range_block(&kvm_tdx->td, gpa, tdx_level, &entry, &level_state); - if (unlikely(tdx_operand_busy(err))) { - /* After no vCPUs enter, the second retry is expected to succeed */ - tdx_no_vcpus_enter_start(kvm); - err = tdh_mem_range_block(&kvm_tdx->td, gpa, tdx_level, &entry, &level_state); - tdx_no_vcpus_enter_stop(kvm); - } - + err = tdh_do_no_vcpus(tdh_mem_range_block, kvm, &kvm_tdx->td, gpa, + tdx_level, &entry, &level_state); if (TDX_BUG_ON_2(err, TDH_MEM_RANGE_BLOCK, entry, level_state, kvm)) return;
@@ -1792,20 +1778,8 @@ static void tdx_sept_remove_private_spte(struct kvm *kvm, gfn_t gfn, * with other vcpu sept operation. * Race with TDH.VP.ENTER due to (0-step mitigation) and Guest TDCALLs. */ - err = tdh_mem_page_remove(&kvm_tdx->td, gpa, tdx_level, &entry, - &level_state); - - if (unlikely(tdx_operand_busy(err))) { - /* - * The second retry is expected to succeed after kicking off all - * other vCPUs and prevent them from invoking TDH.VP.ENTER. - */ - tdx_no_vcpus_enter_start(kvm); - err = tdh_mem_page_remove(&kvm_tdx->td, gpa, tdx_level, &entry, - &level_state); - tdx_no_vcpus_enter_stop(kvm); - } - + err = tdh_do_no_vcpus(tdh_mem_page_remove, kvm, &kvm_tdx->td, gpa, + tdx_level, &entry, &level_state); if (TDX_BUG_ON_2(err, TDH_MEM_PAGE_REMOVE, entry, level_state, kvm)) return;
--
2.51.0.858.gf9c4a03a3a-goog