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

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Date:   Fri,  1 Feb 2019 00:09:23 +0800
From:   Yu Zhang <yu.c.zhang@...ux.intel.com>
To:     kvm@...r.kernel.org
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org
Subject: [PATCH] KVM: MMU: record maximum physical address width in kvm_mmu_extended_role

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: Paolo Bonzini <pbonzini@...hat.com>
Cc: "Radim Krčmář" <rkrcmar@...hat.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Borislav Petkov <bp@...en8.de>
Cc: "H. Peter Anvin" <hpa@...or.com>
Cc: linux-kernel@...r.kernel.org
---
 arch/x86/include/asm/kvm_host.h | 1 +
 arch/x86/kvm/mmu.c              | 1 +
 2 files changed, 2 insertions(+)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 4660ce9..be87f71 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -299,6 +299,7 @@ struct kvm_mmu_memory_cache {
 		unsigned int cr4_smap:1;
 		unsigned int cr4_smep:1;
 		unsigned int cr4_la57:1;
+		unsigned int maxphyaddr:6;
 	};
 };
 
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index ce770b4..2b74505 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -4769,6 +4769,7 @@ static union kvm_mmu_extended_role kvm_calc_mmu_role_ext(struct kvm_vcpu *vcpu)
 	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;
 
-- 
1.9.1