From: Sean Christopherson <seanjc@google.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
Yu Zhang <yu.c.zhang@linux.intel.com>,
Maxim Levitsky <mlevitsk@redhat.com>
Subject: [PATCH 13/54] KVM: x86/mmu: Rename unsync helper and update related comments
Date: Tue, 22 Jun 2021 10:56:58 -0700 [thread overview]
Message-ID: <20210622175739.3610207-14-seanjc@google.com> (raw)
In-Reply-To: <20210622175739.3610207-1-seanjc@google.com>
Rename mmu_need_write_protect() to mmu_try_to_unsync_pages() and update
a variety of related, stale comments. Add several new comments to call
out subtle details, e.g. that upper-level shadow pages are write-tracked,
and that can_unsync is false iff KVM is in the process of synchronizing
pages.
No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/kvm/mmu/mmu.c | 34 ++++++++++++++++++++++++---------
arch/x86/kvm/mmu/mmu_internal.h | 3 +--
arch/x86/kvm/mmu/spte.c | 10 ++++++++--
3 files changed, 34 insertions(+), 13 deletions(-)
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 77296ce6215f..0171c245ecc7 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -2458,17 +2458,33 @@ static void kvm_unsync_page(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp)
kvm_mmu_mark_parents_unsync(sp);
}
-bool mmu_need_write_protect(struct kvm_vcpu *vcpu, gfn_t gfn,
- bool can_unsync)
+/*
+ * Attempt to unsync any shadow pages that can be reached by the specified gfn,
+ * KVM is creating a writable mapping for said gfn. Returns 0 if all pages
+ * were marked unsync (or if there is no shadow page), -EPERM if the SPTE must
+ * be write-protected.
+ */
+int mmu_try_to_unsync_pages(struct kvm_vcpu *vcpu, gfn_t gfn, bool can_unsync)
{
struct kvm_mmu_page *sp;
+ /*
+ * Force write-protection if the page is being tracked. Note, the page
+ * track machinery is used to write-protect upper-level shadow pages,
+ * i.e. this guards the role.level == 4K assertion below!
+ */
if (kvm_page_track_is_active(vcpu, gfn, KVM_PAGE_TRACK_WRITE))
- return true;
+ return -EPERM;
+ /*
+ * The page is not write-tracked, mark existing shadow pages unsync
+ * unless KVM is synchronizing an unsync SP (can_unsync = false). In
+ * that case, KVM must complete emulation of the guest TLB flush before
+ * allowing shadow pages to become unsync (writable by the guest).
+ */
for_each_gfn_indirect_valid_sp(vcpu->kvm, sp, gfn) {
if (!can_unsync)
- return true;
+ return -EPERM;
if (sp->unsync)
continue;
@@ -2499,8 +2515,8 @@ bool mmu_need_write_protect(struct kvm_vcpu *vcpu, gfn_t gfn,
* 2.2 Guest issues TLB flush.
* That causes a VM Exit.
*
- * 2.3 kvm_mmu_sync_pages() reads sp->unsync.
- * Since it is false, so it just returns.
+ * 2.3 Walking of unsync pages sees sp->unsync is
+ * false and skips the page.
*
* 2.4 Guest accesses GVA X.
* Since the mapping in the SP was not updated,
@@ -2516,7 +2532,7 @@ bool mmu_need_write_protect(struct kvm_vcpu *vcpu, gfn_t gfn,
*/
smp_wmb();
- return false;
+ return 0;
}
static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
@@ -3461,8 +3477,8 @@ void kvm_mmu_sync_roots(struct kvm_vcpu *vcpu)
* flush strictly after those changes are made. We only need to
* ensure that the other CPU sets these flags before any actual
* changes to the page tables are made. The comments in
- * mmu_need_write_protect() describe what could go wrong if this
- * requirement isn't satisfied.
+ * mmu_try_to_unsync_pages() describe what could go wrong if
+ * this requirement isn't satisfied.
*/
if (!smp_load_acquire(&sp->unsync) &&
!smp_load_acquire(&sp->unsync_children))
diff --git a/arch/x86/kvm/mmu/mmu_internal.h b/arch/x86/kvm/mmu/mmu_internal.h
index 18be103df9d5..35567293c1fd 100644
--- a/arch/x86/kvm/mmu/mmu_internal.h
+++ b/arch/x86/kvm/mmu/mmu_internal.h
@@ -122,8 +122,7 @@ static inline bool is_nx_huge_page_enabled(void)
return READ_ONCE(nx_huge_pages);
}
-bool mmu_need_write_protect(struct kvm_vcpu *vcpu, gfn_t gfn,
- bool can_unsync);
+int mmu_try_to_unsync_pages(struct kvm_vcpu *vcpu, gfn_t gfn, bool can_unsync);
void kvm_mmu_gfn_disallow_lpage(struct kvm_memory_slot *slot, gfn_t gfn);
void kvm_mmu_gfn_allow_lpage(struct kvm_memory_slot *slot, gfn_t gfn);
diff --git a/arch/x86/kvm/mmu/spte.c b/arch/x86/kvm/mmu/spte.c
index 8e8e8da740a0..246e61e0771e 100644
--- a/arch/x86/kvm/mmu/spte.c
+++ b/arch/x86/kvm/mmu/spte.c
@@ -147,13 +147,19 @@ int make_spte(struct kvm_vcpu *vcpu, unsigned int pte_access, int level,
/*
* Optimization: for pte sync, if spte was writable the hash
* lookup is unnecessary (and expensive). Write protection
- * is responsibility of mmu_get_page / kvm_sync_page.
+ * is responsibility of kvm_mmu_get_page / kvm_mmu_sync_roots.
* Same reasoning can be applied to dirty page accounting.
*/
if (!can_unsync && is_writable_pte(old_spte))
goto out;
- if (mmu_need_write_protect(vcpu, gfn, can_unsync)) {
+ /*
+ * Unsync shadow pages that are reachable by the new, writable
+ * SPTE. Write-protect the SPTE if the page can't be unsync'd,
+ * e.g. it's write-tracked (upper-level SPs) or has one or more
+ * shadow pages and unsync'ing pages is not allowed.
+ */
+ if (mmu_try_to_unsync_pages(vcpu, gfn, can_unsync)) {
pgprintk("%s: found shadow page for %llx, marking ro\n",
__func__, gfn);
ret |= SET_SPTE_WRITE_PROTECTED_PT;
--
2.32.0.288.g62a8d224e6-goog
next prev parent reply other threads:[~2021-06-22 17:59 UTC|newest]
Thread overview: 103+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-22 17:56 [PATCH 00/54] KVM: x86/mmu: Bug fixes and summer cleaning Sean Christopherson
2021-06-22 17:56 ` [PATCH 01/54] KVM: x86/mmu: Remove broken WARN that fires on 32-bit KVM w/ nested EPT Sean Christopherson
2021-06-22 17:56 ` [PATCH 02/54] KVM: x86/mmu: Treat NX as used (not reserved) for all !TDP shadow MMUs Sean Christopherson
2021-06-22 17:56 ` [PATCH 03/54] KVM: x86: Properly reset MMU context at vCPU RESET/INIT Sean Christopherson
2021-06-23 13:59 ` Paolo Bonzini
2021-06-23 14:01 ` Paolo Bonzini
2021-06-23 14:50 ` Sean Christopherson
2021-06-22 17:56 ` [PATCH 04/54] KVM: x86/mmu: Use MMU's role to detect CR4.SMEP value in nested NPT walk Sean Christopherson
2021-06-22 17:56 ` [PATCH 05/54] Revert "KVM: x86/mmu: Drop kvm_mmu_extended_role.cr4_la57 hack" Sean Christopherson
2021-06-25 8:47 ` Yu Zhang
2021-06-25 8:57 ` Paolo Bonzini
2021-06-25 9:29 ` Yu Zhang
2021-06-25 10:25 ` Paolo Bonzini
2021-06-25 11:23 ` Yu Zhang
2021-06-22 17:56 ` [PATCH 06/54] KVM: x86: Force all MMUs to reinitialize if guest CPUID is modified Sean Christopherson
2021-06-22 17:56 ` [PATCH 07/54] KVM: x86: Alert userspace that KVM_SET_CPUID{,2} after KVM_RUN is broken Sean Christopherson
2021-06-23 14:16 ` Paolo Bonzini
2021-06-23 17:00 ` Jim Mattson
2021-06-23 17:11 ` Paolo Bonzini
2021-06-23 18:11 ` Jim Mattson
2021-06-23 18:49 ` Paolo Bonzini
2021-06-23 19:02 ` Jim Mattson
2021-06-23 19:53 ` Paolo Bonzini
2021-06-22 17:56 ` [PATCH 08/54] Revert "KVM: MMU: record maximum physical address width in kvm_mmu_extended_role" Sean Christopherson
2021-06-25 8:52 ` Yu Zhang
2021-06-22 17:56 ` [PATCH 09/54] KVM: x86/mmu: Unconditionally zap unsync SPs when creating >4k SP at GFN Sean Christopherson
2021-06-23 14:36 ` Paolo Bonzini
2021-06-23 15:08 ` Sean Christopherson
2021-06-23 16:38 ` Paolo Bonzini
2021-06-23 22:04 ` Sean Christopherson
2021-06-25 9:51 ` Yu Zhang
2021-06-25 10:26 ` Paolo Bonzini
2021-06-25 13:08 ` Yu Zhang
2021-06-22 17:56 ` [PATCH 10/54] KVM: x86/mmu: Replace EPT shadow page shenanigans with simpler check Sean Christopherson
2021-06-23 15:49 ` Paolo Bonzini
2021-06-23 16:17 ` Sean Christopherson
2021-06-23 16:41 ` Paolo Bonzini
2021-06-23 16:54 ` Sean Christopherson
2021-06-22 17:56 ` [PATCH 11/54] KVM: x86/mmu: WARN and zap SP when sync'ing if MMU role mismatches Sean Christopherson
2021-06-22 17:56 ` [PATCH 12/54] KVM: x86/mmu: Drop the intermediate "transient" __kvm_sync_page() Sean Christopherson
2021-06-23 16:54 ` Paolo Bonzini
2021-06-22 17:56 ` Sean Christopherson [this message]
2021-06-22 17:56 ` [PATCH 14/54] KVM: x86: Fix sizes used to pass around CR0, CR4, and EFER Sean Christopherson
2021-06-22 17:57 ` [PATCH 15/54] KVM: nSVM: Add a comment to document why nNPT uses vmcb01, not vCPU state Sean Christopherson
2021-06-23 17:06 ` Paolo Bonzini
2021-06-23 20:49 ` Sean Christopherson
2021-06-22 17:57 ` [PATCH 16/54] KVM: x86/mmu: Drop smep_andnot_wp check from "uses NX" for shadow MMUs Sean Christopherson
2021-06-23 17:11 ` Paolo Bonzini
2021-06-23 19:36 ` Sean Christopherson
2021-06-22 17:57 ` [PATCH 17/54] KVM: x86: Read and pass all CR0/CR4 role bits to shadow MMU helper Sean Christopherson
2021-06-22 17:57 ` [PATCH 18/54] KVM: x86/mmu: Move nested NPT reserved bit calculation into MMU proper Sean Christopherson
2021-06-23 17:13 ` Paolo Bonzini
2021-06-22 17:57 ` [PATCH 19/54] KVM: x86/mmu: Grab shadow root level from mmu_role for shadow MMUs Sean Christopherson
2021-06-22 17:57 ` [PATCH 20/54] KVM: x86/mmu: Add struct and helpers to retrieve MMU role bits from regs Sean Christopherson
2021-06-23 1:58 ` kernel test robot
2021-06-23 17:18 ` Paolo Bonzini
2021-06-22 17:57 ` [PATCH 21/54] KVM: x86/mmu: Consolidate misc updates into shadow_mmu_init_context() Sean Christopherson
2021-06-22 17:57 ` [PATCH 22/54] KVM: x86/mmu: Ignore CR0 and CR4 bits in nested EPT MMU role Sean Christopherson
2021-06-22 17:57 ` [PATCH 23/54] KVM: x86/mmu: Use MMU's role_regs, not vCPU state, to compute mmu_role Sean Christopherson
2021-06-22 17:57 ` [PATCH 24/54] KVM: x86/mmu: Rename "nxe" role bit to "efer_nx" for macro shenanigans Sean Christopherson
2021-06-22 17:57 ` [PATCH 25/54] KVM: x86/mmu: Add helpers to query mmu_role bits Sean Christopherson
2021-06-23 20:02 ` Paolo Bonzini
2021-06-23 20:47 ` Sean Christopherson
2021-06-23 20:53 ` Paolo Bonzini
2021-06-22 17:57 ` [PATCH 26/54] KVM: x86/mmu: Do not set paging-related bits in MMU role if CR0.PG=0 Sean Christopherson
2021-06-22 17:57 ` [PATCH 27/54] KVM: x86/mmu: Set CR4.PKE/LA57 in MMU role iff long mode is active Sean Christopherson
2021-06-22 17:57 ` [PATCH 28/54] KVM: x86/mmu: Always Set new mmu_role immediately after checking old role Sean Christopherson
2021-06-22 17:57 ` [PATCH 29/54] KVM: x86/mmu: Don't grab CR4.PSE for calculating shadow reserved bits Sean Christopherson
2021-06-22 17:57 ` [PATCH 30/54] KVM: x86/mmu: Use MMU's role to get CR4.PSE for computing rsvd bits Sean Christopherson
2021-06-22 17:57 ` [PATCH 31/54] KVM: x86/mmu: Drop vCPU param from reserved bits calculator Sean Christopherson
2021-06-22 17:57 ` [PATCH 32/54] KVM: x86/mmu: Use MMU's role to compute permission bitmask Sean Christopherson
2021-06-22 17:57 ` [PATCH 33/54] KVM: x86/mmu: Use MMU's role to compute PKRU bitmask Sean Christopherson
2021-06-22 17:57 ` [PATCH 34/54] KVM: x86/mmu: Use MMU's roles to compute last non-leaf level Sean Christopherson
2021-06-22 17:57 ` [PATCH 35/54] KVM: x86/mmu: Use MMU's role to detect EFER.NX in guest page walk Sean Christopherson
2021-06-22 17:57 ` [PATCH 36/54] KVM: x86/mmu: Use MMU's role/role_regs to compute context's metadata Sean Christopherson
2021-06-22 17:57 ` [PATCH 37/54] KVM: x86/mmu: Use MMU's role to get EFER.NX during MMU configuration Sean Christopherson
2021-06-22 17:57 ` [PATCH 38/54] KVM: x86/mmu: Drop "nx" from MMU context now that there are no readers Sean Christopherson
2021-06-22 17:57 ` [PATCH 39/54] KVM: x86/mmu: Get nested MMU's root level from the MMU's role Sean Christopherson
2021-06-22 17:57 ` [PATCH 40/54] KVM: x86/mmu: Use MMU role_regs to get LA57, and drop vCPU LA57 helper Sean Christopherson
2021-06-22 17:57 ` [PATCH 41/54] KVM: x86/mmu: Consolidate reset_rsvds_bits_mask() calls Sean Christopherson
2021-06-23 20:07 ` Paolo Bonzini
2021-06-23 20:53 ` Sean Christopherson
2021-06-22 17:57 ` [PATCH 42/54] KVM: x86/mmu: Don't update nested guest's paging bitmasks if CR0.PG=0 Sean Christopherson
2021-06-22 17:57 ` [PATCH 43/54] KVM: x86/mmu: Add helper to update paging metadata Sean Christopherson
2021-06-22 17:57 ` [PATCH 44/54] KVM: x86/mmu: Add a helper to calculate root from role_regs Sean Christopherson
2021-06-22 17:57 ` [PATCH 45/54] KVM: x86/mmu: Collapse 32-bit PAE and 64-bit statements for helpers Sean Christopherson
2021-06-22 17:57 ` [PATCH 46/54] KVM: x86/mmu: Use MMU's role to determine PTTYPE Sean Christopherson
2021-06-22 17:57 ` [PATCH 47/54] KVM: x86/mmu: Add helpers to do full reserved SPTE checks w/ generic MMU Sean Christopherson
2021-06-23 20:13 ` Paolo Bonzini
2021-06-22 17:57 ` [PATCH 48/54] KVM: x86/mmu: WARN on any reserved SPTE value when making a valid SPTE Sean Christopherson
2021-06-22 17:57 ` [PATCH 49/54] KVM: x86: Enhance comments for MMU roles and nested transition trickiness Sean Christopherson
2021-06-22 17:57 ` [PATCH 50/54] KVM: x86/mmu: Optimize and clean up so called "last nonleaf level" logic Sean Christopherson
2021-06-23 20:22 ` Paolo Bonzini
2021-06-23 20:58 ` Sean Christopherson
2021-06-22 17:57 ` [PATCH 51/54] KVM: x86/mmu: Drop redundant rsvd bits reset for nested NPT Sean Christopherson
2021-06-22 17:57 ` [PATCH 52/54] KVM: x86/mmu: Get CR0.WP from MMU, not vCPU, in shadow page fault Sean Christopherson
2021-06-22 17:57 ` [PATCH 53/54] KVM: x86/mmu: Get CR4.SMEP " Sean Christopherson
2021-06-22 17:57 ` [PATCH 54/54] KVM: x86/mmu: Let guest use GBPAGES if supported in hardware and TDP is on Sean Christopherson
2021-06-23 20:29 ` [PATCH 00/54] KVM: x86/mmu: Bug fixes and summer cleaning Paolo Bonzini
2021-06-23 21:06 ` Sean Christopherson
2021-06-23 21:33 ` Paolo Bonzini
2021-06-23 22:08 ` Sean Christopherson
2021-06-23 22:12 ` Paolo Bonzini
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