Commit 550ba57f authored by Sean Christopherson's avatar Sean Christopherson
Browse files

KVM: VMX: Drop unnecessary vmx_fb_clear_ctrl_available "cache" 



Now that KVM snapshots the host's MSR_IA32_ARCH_CAPABILITIES, drop the
similar snapshot/cache of whether or not KVM is allowed to manipulate
MSR_IA32_MCU_OPT_CTRL.FB_CLEAR_DIS.  The motivation for the cache was
presumably to avoid the RDMSR, e.g. boot_cpu_has_bug() is quite cheap, and
modifying the vCPU's MSR_IA32_ARCH_CAPABILITIES is an infrequent option
and a relatively slow path.

Cc: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Reviewed-by: default avatarPawan Gupta <pawan.kumar.gupta@linux.intel.com>
Reviewed-by: default avatarXiaoyao Li <xiaoyao.li@intel.com>
Link: https://lore.kernel.org/r/20230607004311.1420507-3-seanjc@google.com


Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
parent a2fd5d02

arch/x86/kvm/vmx/vmx.c

+3 −14
Original line number Diff line number Diff line
@@ -237,9 +237,6 @@ static const struct { 
#define L1D_CACHE_ORDER 4

static void *vmx_l1d_flush_pages;



/* Control for disabling CPU Fill buffer clear */

static bool __read_mostly vmx_fb_clear_ctrl_available;



static int vmx_setup_l1d_flush(enum vmx_l1d_flush_state l1tf)

{

	struct page *page;
@@ -366,14 +363,6 @@ static int vmentry_l1d_flush_get(char *s, const struct kernel_param *kp) 
	return sysfs_emit(s, "%s\n", vmentry_l1d_param[l1tf_vmx_mitigation].option);

}



static void vmx_setup_fb_clear_ctrl(void)

{

	if ((host_arch_capabilities & ARCH_CAP_FB_CLEAR_CTRL) &&

	    !boot_cpu_has_bug(X86_BUG_MDS) &&

	    !boot_cpu_has_bug(X86_BUG_TAA))

		vmx_fb_clear_ctrl_available = true;

}



static __always_inline void vmx_disable_fb_clear(struct vcpu_vmx *vmx)

{

	u64 msr;
@@ -399,7 +388,9 @@ static __always_inline void vmx_enable_fb_clear(struct vcpu_vmx *vmx) 


static void vmx_update_fb_clear_dis(struct kvm_vcpu *vcpu, struct vcpu_vmx *vmx)

{

	vmx->disable_fb_clear = vmx_fb_clear_ctrl_available;

	vmx->disable_fb_clear = (host_arch_capabilities & ARCH_CAP_FB_CLEAR_CTRL) &&

				!boot_cpu_has_bug(X86_BUG_MDS) &&

				!boot_cpu_has_bug(X86_BUG_TAA);



	/*

	 * If guest will not execute VERW, there is no need to set FB_CLEAR_DIS
@@ -8626,8 +8617,6 @@ static int __init vmx_init(void) 
	if (r)

		goto err_l1d_flush;



	vmx_setup_fb_clear_ctrl();



	for_each_possible_cpu(cpu) {

		INIT_LIST_HEAD(&per_cpu(loaded_vmcss_on_cpu, cpu));