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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>,
	Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Subject: [PATCH 4.14 21/23] KVM: x86/mmu: Treat NX as used (not reserved) for all !TDP shadow MMUs
Date: Wed,  1 Sep 2021 14:27:06 +0200	[thread overview]
Message-ID: <20210901122250.465576312@linuxfoundation.org> (raw)
In-Reply-To: <20210901122249.786673285@linuxfoundation.org>

From: Sean Christopherson <seanjc@google.com>

commit 112022bdb5bc372e00e6e43cb88ee38ea67b97bd upstream

Mark NX as being used for all non-nested shadow MMUs, as KVM will set the
NX bit for huge SPTEs if the iTLB mutli-hit mitigation is enabled.
Checking the mitigation itself is not sufficient as it can be toggled on
at any time and KVM doesn't reset MMU contexts when that happens.  KVM
could reset the contexts, but that would require purging all SPTEs in all
MMUs, for no real benefit.  And, KVM already forces EFER.NX=1 when TDP is
disabled (for WP=0, SMEP=1, NX=0), so technically NX is never reserved
for shadow MMUs.

Fixes: b8e8c8303ff2 ("kvm: mmu: ITLB_MULTIHIT mitigation")
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
[sudip: use old path and adjust context]
Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 arch/x86/kvm/mmu.c |   11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -4326,7 +4326,16 @@ static void reset_rsvds_bits_mask_ept(st
 void
 reset_shadow_zero_bits_mask(struct kvm_vcpu *vcpu, struct kvm_mmu *context)
 {
-	bool uses_nx = context->nx || context->base_role.smep_andnot_wp;
+	/*
+	 * KVM uses NX when TDP is disabled to handle a variety of scenarios,
+	 * notably for huge SPTEs if iTLB multi-hit mitigation is enabled and
+	 * to generate correct permissions for CR0.WP=0/CR4.SMEP=1/EFER.NX=0.
+	 * The iTLB multi-hit workaround can be toggled at any time, so assume
+	 * NX can be used by any non-nested shadow MMU to avoid having to reset
+	 * MMU contexts.  Note, KVM forces EFER.NX=1 when TDP is disabled.
+	 */
+	bool uses_nx = context->nx || !tdp_enabled ||
+		context->base_role.smep_andnot_wp;
 	struct rsvd_bits_validate *shadow_zero_check;
 	int i;
 



  parent reply	other threads:[~2021-09-01 12:29 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-01 12:26 [PATCH 4.14 00/23] 4.14.246-rc1 review Greg Kroah-Hartman
2021-09-01 12:26 ` [PATCH 4.14 01/23] ARC: Fix CONFIG_STACKDEPOT Greg Kroah-Hartman
2021-09-01 12:26 ` [PATCH 4.14 02/23] can: usb: esd_usb2: esd_usb2_rx_event(): fix the interchange of the CAN RX and TX error counters Greg Kroah-Hartman
2021-09-01 12:26 ` [PATCH 4.14 03/23] Revert "USB: serial: ch341: fix character loss at high transfer rates" Greg Kroah-Hartman
2021-09-01 12:26 ` [PATCH 4.14 04/23] USB: serial: option: add new VID/PID to support Fibocom FG150 Greg Kroah-Hartman
2021-09-01 12:26 ` [PATCH 4.14 05/23] usb: dwc3: gadget: Fix dwc3_calc_trbs_left() Greg Kroah-Hartman
2021-09-01 12:26 ` [PATCH 4.14 06/23] usb: dwc3: gadget: Stop EP0 transfers during pullup disable Greg Kroah-Hartman
2021-09-01 12:26 ` [PATCH 4.14 07/23] IB/hfi1: Fix possible null-pointer dereference in _extend_sdma_tx_descs() Greg Kroah-Hartman
2021-09-01 12:26 ` [PATCH 4.14 08/23] e1000e: Fix the max snoop/no-snoop latency for 10M Greg Kroah-Hartman
2021-09-01 12:26 ` [PATCH 4.14 09/23] ip_gre: add validation for csum_start Greg Kroah-Hartman
2021-09-01 12:26 ` [PATCH 4.14 10/23] xgene-v2: Fix a resource leak in the error handling path of xge_probe() Greg Kroah-Hartman
2021-09-01 12:26 ` [PATCH 4.14 11/23] net: marvell: fix MVNETA_TX_IN_PRGRS bit number Greg Kroah-Hartman
2021-09-01 12:26 ` [PATCH 4.14 12/23] usb: gadget: u_audio: fix race condition on endpoint stop Greg Kroah-Hartman
2021-09-01 12:26 ` [PATCH 4.14 13/23] opp: remove WARN when no valid OPPs remain Greg Kroah-Hartman
2021-09-01 12:26 ` [PATCH 4.14 14/23] virtio: Improve vq->broken access to avoid any compiler optimization Greg Kroah-Hartman
2021-09-01 12:27 ` [PATCH 4.14 15/23] vringh: Use wiov->used to check for read/write desc order Greg Kroah-Hartman
2021-09-01 12:27 ` [PATCH 4.14 16/23] drm: Copy drm_wait_vblank to user before returning Greg Kroah-Hartman
2021-09-01 12:27 ` [PATCH 4.14 17/23] drm/nouveau/disp: power down unused DP links during init Greg Kroah-Hartman
2021-09-01 12:27 ` [PATCH 4.14 18/23] net/rds: dma_map_sg is entitled to merge entries Greg Kroah-Hartman
2021-09-01 12:27 ` [PATCH 4.14 19/23] vt_kdsetmode: extend console locking Greg Kroah-Hartman
2021-09-01 12:27 ` [PATCH 4.14 20/23] fbmem: add margin check to fb_check_caps() Greg Kroah-Hartman
2021-09-01 12:27 ` Greg Kroah-Hartman [this message]
2021-09-01 12:27 ` [PATCH 4.14 22/23] KVM: X86: MMU: Use the correct inherited permissions to get shadow page Greg Kroah-Hartman
2021-09-01 12:27 ` [PATCH 4.14 23/23] Revert "floppy: reintroduce O_NDELAY fix" Greg Kroah-Hartman
2021-09-01 19:21 ` [PATCH 4.14 00/23] 4.14.246-rc1 review Jon Hunter
2021-09-01 19:22 ` Jon Hunter
2021-09-02  1:08 ` Samuel Zou
2021-09-02 16:08 ` Naresh Kamboju
2021-09-02 21:50 ` Guenter Roeck

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