linux-kernel - [PATCH 4.20 163/183] KVM: MMU: record maximum physical address width in kvm_mmu_extended

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Date:   Mon, 25 Feb 2019 22:12:16 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Yu Zhang <yu.c.zhang@...ux.intel.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: [PATCH 4.20 163/183] KVM: MMU: record maximum physical address width in kvm_mmu_extended_role

4.20-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Yu Zhang <yu.c.zhang@...ux.intel.com>

commit de3ccd26fafc707b09792d9b633c8b5b48865315 upstream.

Previously, commit 7dcd57552008 ("x86/kvm/mmu: check if tdp/shadow
MMU reconfiguration is needed") offered some optimization to avoid
the unnecessary reconfiguration. Yet one scenario is broken - when
cpuid changes VM's maximum physical address width, reconfiguration
is needed to reset the reserved bits.  Also, the TDP may need to
reset its shadow_root_level when this value is changed.

To fix this, a new field, maxphyaddr, is introduced in the extended
role structure to keep track of the configured guest physical address
width.

Signed-off-by: Yu Zhang <yu.c.zhang@...ux.intel.com>
Cc: stable@...r.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/x86/include/asm/kvm_host.h |    1 +
 arch/x86/kvm/mmu.c              |    1 +
 2 files changed, 2 insertions(+)

--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -299,6 +299,7 @@ union kvm_mmu_extended_role {
 		unsigned int cr4_smap:1;
 		unsigned int cr4_smep:1;
 		unsigned int cr4_la57:1;
+		unsigned int maxphyaddr:6;
 	};
 };
 
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -4731,6 +4731,7 @@ static union kvm_mmu_extended_role kvm_c
 	ext.cr4_pse = !!is_pse(vcpu);
 	ext.cr4_pke = !!kvm_read_cr4_bits(vcpu, X86_CR4_PKE);
 	ext.cr4_la57 = !!kvm_read_cr4_bits(vcpu, X86_CR4_LA57);
+	ext.maxphyaddr = cpuid_maxphyaddr(vcpu);
 
 	ext.valid = 1;