KVM: nVMX: Reset register cache (available and dirty masks) on VMCS switch (e5d03de5) · Commits · 戴 / test

Reset the per-vCPU available and dirty register masks when switching between vmcs01 and vmcs02, as the masks track state relative to the current VMCS. The stale masks don't cause problems in the current code base because the registers are either unconditionally written on nested transitions or, in the case of segment registers, have an additional tracker that is manually reset. Note, by dropping (previously implicitly, now explicitly) the dirty mask when switching the active VMCS, KVM is technically losing writes to the associated fields. But, the only regs that can be dirtied (RIP, RSP and PDPTRs) are unconditionally written on nested transitions, e.g. explicit writeback is a waste of cycles, and a WARN_ON would be rather pointless. Signed-off-by:

Sean Christopherson <sean.j.christopherson@intel.com> Message-Id: <20200415203454.8296-3-sean.j.christopherson@intel.com> Signed-off-by:

Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/vmx/nested.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -307,6 +307,7 @@ static void vmx_switch_vmcs(struct kvm_vcpu vcpu, struct loaded_vmcs vmcs)
		vmx_sync_vmcs_host_state(vmx, prev);
		put_cpu();

		vmx_register_cache_reset(vcpu);
		vmx_segment_cache_clear(vmx);
		}

arch/x86/kvm/vmx/vmx.c

+1 −6

Original line number	Diff line number	Diff line
		@@ -6711,12 +6711,7 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu)
		loadsegment(es, __USER_DS);
		#endif

		vcpu->arch.regs_avail = ~((1 << VCPU_REGS_RIP) \| (1 << VCPU_REGS_RSP)
		\| (1 << VCPU_EXREG_RFLAGS)
		\| (1 << VCPU_EXREG_PDPTR)
		\| (1 << VCPU_EXREG_SEGMENTS)
		\| (1 << VCPU_EXREG_CR3));
		vcpu->arch.regs_dirty = 0;
		vmx_register_cache_reset(vcpu);

		pt_guest_exit(vmx);

arch/x86/kvm/vmx/vmx.h

+11 −0

Original line number	Diff line number	Diff line
		@@ -8,6 +8,7 @@
		#include <asm/intel_pt.h>

		#include "capabilities.h"
		#include "kvm_cache_regs.h"
		#include "ops.h"
		#include "vmcs.h"

		@@ -447,6 +448,16 @@ static inline void vmx_segment_cache_clear(struct vcpu_vmx *vmx)
		vmx->segment_cache.bitmask = 0;
		}

		static inline void vmx_register_cache_reset(struct kvm_vcpu *vcpu)
		{
		vcpu->arch.regs_avail = ~((1 << VCPU_REGS_RIP) \| (1 << VCPU_REGS_RSP)
		\| (1 << VCPU_EXREG_RFLAGS)
		\| (1 << VCPU_EXREG_PDPTR)
		\| (1 << VCPU_EXREG_SEGMENTS)
		\| (1 << VCPU_EXREG_CR3));
		vcpu->arch.regs_dirty = 0;
		}

		static inline u32 vmx_vmentry_ctrl(void)
		{
		u32 vmentry_ctrl = vmcs_config.vmentry_ctrl;

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