admin/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2025-12-07 20:06:24 +00:00
Code Issues Packages Projects Releases Wiki Activity

KVM: TDX: Add macro to retry SEAMCALLs when forcing vCPUs out of guest

Browse Source 
Add a macro to handle kicking vCPUs out of the guest and retrying
SEAMCALLs on TDX_OPERAND_BUSY 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.

Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Reviewed-by: Yan Zhao <yan.y.zhao@intel.com>
Tested-by: Yan Zhao <yan.y.zhao@intel.com>
Tested-by: Kai Huang <kai.huang@intel.com>
Link: https://patch.msgid.link/20251030200951.3402865-22-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Sean Christopherson
2025-10-30 13:09:44 -07:00
parent 2ff1411698
commit 3d626ce5a8
1 changed files with 33 additions and 49 deletions
Download Patch File Download Diff File Expand all files Collapse all files

82
arch/x86/kvm/vmx/tdx.c
View File

@@ -294,25 +294,34 @@ 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);
}
/*
* Execute a SEAMCALL related to removing/blocking S-EPT entries, with a single
* retry (if necessary) after forcing vCPUs to exit and wait for the operation
* to complete. All flows that remove/block S-EPT entries run with mmu_lock
* held for write, i.e. are mutually exclusive with each other, but they aren't
* mutually exclusive with running vCPUs, and so can fail with "operand busy"
* if a vCPU acquires a relevant lock in the TDX-Module, e.g. when doing TDCALL.
*
* Note, the retry is guaranteed to succeed, absent KVM and/or TDX-Module bugs.
*/
#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)
@@ -1722,14 +1731,7 @@ static void tdx_track(struct kvm *kvm)
*/
lockdep_assert_held_write(&kvm->mmu_lock);
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);
@@ -1781,14 +1783,8 @@ 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;
@@ -1803,20 +1799,8 @@ 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;