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From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	stable@vger.kernel.org, Sean Christopherson <seanjc@google.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.11 02/31] KVM: x86/mmu: Expand on the comment in kvm_vcpu_ad_need_write_protect()
Date: Fri, 19 Mar 2021 13:18:56 +0100	[thread overview]
Message-ID: <20210319121747.290778628@linuxfoundation.org> (raw)
In-Reply-To: <20210319121747.203523570@linuxfoundation.org>

From: Sean Christopherson <seanjc@google.com>

[ Upstream commit 2855f98265dc579bd2becb79ce0156d08e0df813 ]

Expand the comment about need to use write-protection for nested EPT
when PML is enabled to clarify that the tagging is a nop when PML is
_not_ enabled.  Without the clarification, omitting the PML check looks
wrong at first^Wfifth glance.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210213005015.1651772-8-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 arch/x86/kvm/mmu/mmu_internal.h | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/mmu/mmu_internal.h b/arch/x86/kvm/mmu/mmu_internal.h
index bfc6389edc28..8404145fb179 100644
--- a/arch/x86/kvm/mmu/mmu_internal.h
+++ b/arch/x86/kvm/mmu/mmu_internal.h
@@ -79,7 +79,10 @@ static inline bool kvm_vcpu_ad_need_write_protect(struct kvm_vcpu *vcpu)
 	 * When using the EPT page-modification log, the GPAs in the log
 	 * would come from L2 rather than L1.  Therefore, we need to rely
 	 * on write protection to record dirty pages.  This also bypasses
-	 * PML, since writes now result in a vmexit.
+	 * PML, since writes now result in a vmexit.  Note, this helper will
+	 * tag SPTEs as needing write-protection even if PML is disabled or
+	 * unsupported, but that's ok because the tag is consumed if and only
+	 * if PML is enabled.  Omit the PML check to save a few uops.
 	 */
 	return vcpu->arch.mmu == &vcpu->arch.guest_mmu;
 }
-- 
2.30.1




  parent reply	other threads:[~2021-03-19 12:21 UTC|newest]

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-19 12:18 [PATCH 5.11 00/31] 5.11.8-rc1 review Greg Kroah-Hartman
2021-03-19 12:18 ` [PATCH 5.11 01/31] io_uring: dont attempt IO reissue from the ring exit path Greg Kroah-Hartman
2021-03-19 12:18 ` Greg Kroah-Hartman [this message]
2021-03-19 12:18 ` [PATCH 5.11 03/31] KVM: x86/mmu: Set SPTE_AD_WRPROT_ONLY_MASK if and only if PML is enabled Greg Kroah-Hartman
2021-03-19 12:18 ` [PATCH 5.11 04/31] mptcp: send ack for every add_addr Greg Kroah-Hartman
2021-03-19 12:18 ` [PATCH 5.11 05/31] mptcp: pm: add lockdep assertions Greg Kroah-Hartman
2021-03-19 12:19 ` [PATCH 5.11 06/31] mptcp: dispose initial struct socket when its subflow is closed Greg Kroah-Hartman
2021-03-19 12:19 ` [PATCH 5.11 07/31] io_uring: refactor scheduling in io_cqring_wait Greg Kroah-Hartman
2021-03-19 12:19 ` [PATCH 5.11 08/31] io_uring: refactor io_cqring_wait Greg Kroah-Hartman
2021-03-19 12:19 ` [PATCH 5.11 09/31] io_uring: dont keep looping for more events if we cant flush overflow Greg Kroah-Hartman
2021-03-19 12:19 ` [PATCH 5.11 10/31] io_uring: simplify do_read return parsing Greg Kroah-Hartman
2021-03-19 12:19 ` [PATCH 5.11 11/31] io_uring: clear IOCB_WAITQ for non -EIOCBQUEUED return Greg Kroah-Hartman
2021-03-19 12:19 ` [PATCH 5.11 12/31] gpiolib: Read "gpio-line-names" from a firmware node Greg Kroah-Hartman
2021-03-19 12:27   ` Marek Vasut
2021-03-19 12:36     ` Greg Kroah-Hartman
2021-03-19 12:45       ` Marek Vasut
2021-03-19 12:19 ` [PATCH 5.11 13/31] net: bonding: fix error return code of bond_neigh_init() Greg Kroah-Hartman
2021-03-19 14:12   ` Jiri Kosina
2021-03-19 14:24     ` Jiri Kosina
2021-03-19 14:29       ` Greg Kroah-Hartman
2021-03-19 14:25     ` Greg Kroah-Hartman
2021-03-19 15:14       ` Jiri Kosina
2021-03-19 12:19 ` [PATCH 5.11 14/31] regulator: pca9450: Add SD_VSEL GPIO for LDO5 Greg Kroah-Hartman
2021-03-19 12:19 ` [PATCH 5.11 15/31] regulator: pca9450: Enable system reset on WDOG_B assertion Greg Kroah-Hartman
2021-03-19 12:19 ` [PATCH 5.11 16/31] regulator: pca9450: Clear PRESET_EN bit to fix BUCK1/2/3 voltage setting Greg Kroah-Hartman
2021-03-19 12:19 ` [PATCH 5.11 17/31] gfs2: Add common helper for holding and releasing the freeze glock Greg Kroah-Hartman
2021-03-19 12:19 ` [PATCH 5.11 18/31] gfs2: move freeze glock outside the make_fs_rw and _ro functions Greg Kroah-Hartman
2021-03-19 12:19 ` [PATCH 5.11 19/31] gfs2: bypass signal_our_withdraw if no journal Greg Kroah-Hartman
2021-03-19 12:19 ` [PATCH 5.11 20/31] bpf: Prohibit alu ops for pointer types not defining ptr_limit Greg Kroah-Hartman
2021-03-19 12:19 ` [PATCH 5.11 21/31] bpf: Fix off-by-one for area size in creating mask to left Greg Kroah-Hartman
2021-03-19 12:19 ` [PATCH 5.11 22/31] bpf: Simplify alu_limit masking for pointer arithmetic Greg Kroah-Hartman
2021-03-19 12:19 ` [PATCH 5.11 23/31] bpf: Add sanity check for upper ptr_limit Greg Kroah-Hartman
2021-03-19 12:19 ` [PATCH 5.11 24/31] bpf, selftests: Fix up some test_verifier cases for unprivileged Greg Kroah-Hartman
2021-03-19 12:19 ` [PATCH 5.11 25/31] arm64: Unconditionally set virtual cpu id registers Greg Kroah-Hartman
2021-03-19 12:19 ` [PATCH 5.11 26/31] RDMA/srp: Fix support for unpopulated and unbalanced NUMA nodes Greg Kroah-Hartman
2021-03-19 12:19 ` [PATCH 5.11 27/31] fuse: fix live lock in fuse_iget() Greg Kroah-Hartman
2021-03-19 12:19 ` [PATCH 5.11 28/31] Revert "nfsd4: remove check_conflicting_opens warning" Greg Kroah-Hartman
2021-03-19 12:19 ` [PATCH 5.11 29/31] Revert "nfsd4: a clients own opens neednt prevent delegations" Greg Kroah-Hartman
2021-03-19 12:19 ` [PATCH 5.11 30/31] net: dsa: b53: Support setting learning on port Greg Kroah-Hartman
2021-03-19 12:19 ` [PATCH 5.11 31/31] crypto: x86/aes-ni-xts - use direct calls to and 4-way stride Greg Kroah-Hartman
2021-03-19 19:38 ` [PATCH 5.11 00/31] 5.11.8-rc1 review Naresh Kamboju
2021-03-20  9:52   ` Greg Kroah-Hartman
2021-03-19 21:23 ` Guenter Roeck

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