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Subject[PATCH 4.14 078/115] KVM: vmx: track host_state.loaded using a loaded_vmcs pointer
Date
4.14-stable review patch.  If anyone has any objections, please let me know.

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

From: Sean Christopherson <sean.j.christopherson@intel.com>

[ Upstream commit bd9966de4e14fb559e89a06f7f5c9aab2cc028b9 ]

Using 'struct loaded_vmcs*' to track whether the CPU registers
contain host or guest state kills two birds with one stone.

1. The (effective) boolean host_state.loaded is poorly named.
It does not track whether or not host state is loaded into
the CPU registers (which most readers would expect), but
rather tracks if host state has been saved AND guest state
is loaded.

2. Using a loaded_vmcs pointer provides a more robust framework
for the optimized guest/host state switching, especially when
consideration per-VMCS enhancements. To that end, WARN_ONCE
if we try to switch to host state with a different VMCS than
was last used to save host state.

Resolve an occurrence of the new WARN by setting loaded_vmcs after
the call to vmx_vcpu_put() in vmx_switch_vmcs().

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/x86/kvm/vmx.c | 22 +++++++++++++++-------
1 file changed, 15 insertions(+), 7 deletions(-)

--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -749,17 +749,21 @@ struct vcpu_vmx {
/*
* loaded_vmcs points to the VMCS currently used in this vcpu. For a
* non-nested (L1) guest, it always points to vmcs01. For a nested
- * guest (L2), it points to a different VMCS.
+ * guest (L2), it points to a different VMCS. loaded_cpu_state points
+ * to the VMCS whose state is loaded into the CPU registers that only
+ * need to be switched when transitioning to/from the kernel; a NULL
+ * value indicates that host state is loaded.
*/
struct loaded_vmcs vmcs01;
struct loaded_vmcs *loaded_vmcs;
+ struct loaded_vmcs *loaded_cpu_state;
bool __launched; /* temporary, used in vmx_vcpu_run */
struct msr_autoload {
struct vmx_msrs guest;
struct vmx_msrs host;
} msr_autoload;
+
struct {
- int loaded;
u16 fs_sel, gs_sel, ldt_sel;
#ifdef CONFIG_X86_64
u16 ds_sel, es_sel;
@@ -2336,10 +2340,11 @@ static void vmx_save_host_state(struct k
struct vcpu_vmx *vmx = to_vmx(vcpu);
int i;

- if (vmx->host_state.loaded)
+ if (vmx->loaded_cpu_state)
return;

- vmx->host_state.loaded = 1;
+ vmx->loaded_cpu_state = vmx->loaded_vmcs;
+
/*
* Set host fs and gs selectors. Unfortunately, 22.2.3 does not
* allow segment selectors with cpl > 0 or ti == 1.
@@ -2390,11 +2395,14 @@ static void vmx_save_host_state(struct k

static void __vmx_load_host_state(struct vcpu_vmx *vmx)
{
- if (!vmx->host_state.loaded)
+ if (!vmx->loaded_cpu_state)
return;

+ WARN_ON_ONCE(vmx->loaded_cpu_state != vmx->loaded_vmcs);
+
++vmx->vcpu.stat.host_state_reload;
- vmx->host_state.loaded = 0;
+ vmx->loaded_cpu_state = NULL;
+
#ifdef CONFIG_X86_64
if (is_long_mode(&vmx->vcpu))
rdmsrl(MSR_KERNEL_GS_BASE, vmx->msr_guest_kernel_gs_base);
@@ -9944,8 +9952,8 @@ static void vmx_switch_vmcs(struct kvm_v
return;

cpu = get_cpu();
- vmx->loaded_vmcs = vmcs;
vmx_vcpu_put(vcpu);
+ vmx->loaded_vmcs = vmcs;
vmx_vcpu_load(vcpu, cpu);
vcpu->cpu = cpu;
put_cpu();

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