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Commit 47c61b39 authored by Thomas Gleixner's avatar Thomas Gleixner
Browse files

x86/speculation, KVM: Implement support for VIRT_SPEC_CTRL/LS_CFG 



Add the necessary logic for supporting the emulated VIRT_SPEC_CTRL MSR to
x86_virt_spec_ctrl().  If either X86_FEATURE_LS_CFG_SSBD or
X86_FEATURE_VIRT_SPEC_CTRL is set then use the new guest_virt_spec_ctrl
argument to check whether the state must be modified on the host. The
update reuses speculative_store_bypass_update() so the ZEN-specific sibling
coordination can be reused.

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent be6fcb54

arch/x86/include/asm/spec-ctrl.h

+6 −0
Original line number Diff line number Diff line
@@ -53,6 +53,12 @@ static inline u64 ssbd_tif_to_spec_ctrl(u64 tifn) 
	return (tifn & _TIF_SSBD) >> (TIF_SSBD - SPEC_CTRL_SSBD_SHIFT);

}



static inline unsigned long ssbd_spec_ctrl_to_tif(u64 spec_ctrl)

{

	BUILD_BUG_ON(TIF_SSBD < SPEC_CTRL_SSBD_SHIFT);

	return (spec_ctrl & SPEC_CTRL_SSBD) << (TIF_SSBD - SPEC_CTRL_SSBD_SHIFT);

}



static inline u64 ssbd_tif_to_amd_ls_cfg(u64 tifn)

{

	return (tifn & _TIF_SSBD) ? x86_amd_ls_cfg_ssbd_mask : 0ULL;

arch/x86/kernel/cpu/bugs.c

+30 −0
Original line number Diff line number Diff line
@@ -162,6 +162,36 @@ x86_virt_spec_ctrl(u64 guest_spec_ctrl, u64 guest_virt_spec_ctrl, bool setguest) 
			wrmsrl(MSR_IA32_SPEC_CTRL, msrval);

		}

	}



	/*

	 * If SSBD is not handled in MSR_SPEC_CTRL on AMD, update

	 * MSR_AMD64_L2_CFG or MSR_VIRT_SPEC_CTRL if supported.

	 */

	if (!static_cpu_has(X86_FEATURE_LS_CFG_SSBD) &&

	    !static_cpu_has(X86_FEATURE_VIRT_SSBD))

		return;



	/*

	 * If the host has SSBD mitigation enabled, force it in the host's

	 * virtual MSR value. If its not permanently enabled, evaluate

	 * current's TIF_SSBD thread flag.

	 */

	if (static_cpu_has(X86_FEATURE_SPEC_STORE_BYPASS_DISABLE))

		hostval = SPEC_CTRL_SSBD;

	else

		hostval = ssbd_tif_to_spec_ctrl(ti->flags);



	/* Sanitize the guest value */

	guestval = guest_virt_spec_ctrl & SPEC_CTRL_SSBD;



	if (hostval != guestval) {

		unsigned long tif;



		tif = setguest ? ssbd_spec_ctrl_to_tif(guestval) :

				 ssbd_spec_ctrl_to_tif(hostval);



		speculative_store_bypass_update(tif);

	}

}

EXPORT_SYMBOL_GPL(x86_virt_spec_ctrl);