KVM: MMU: record maximum physical address width in kvm_mmu_extended_role [Linux 5.0]

KVM: MMU: record maximum physical address width in kvm_mmu_extended_role [Linux 5.0]

This Linux kernel change "KVM: MMU: record maximum physical address width in kvm_mmu_extended_role" is included in the Linux 5.0 release. This change is authored by Yu Zhang <yu.c.zhang [at] linux.intel.com> on Fri Feb 1 00:09:23 2019 +0800. The commit for this change in Linux stable tree is de3ccd2 (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 <[email protected]>
Cc: [email protected]
Signed-off-by: Paolo Bonzini <[email protected]>

There are 2 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 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 593e17b..1803733 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 6e62ed3..f2d1d23 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -4777,6 +4777,7 @@ 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;

Leave a Reply

Your email address will not be published. Required fields are marked *