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

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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: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Thomas Gleixner 2018-05-10 20:42:48 +02:00
parent be6fcb5478
commit 47c61b3955
2 changed files with 36 additions and 0 deletions
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6
arch/x86/include/asm/spec-ctrl.h
View File

@ -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;

30
arch/x86/kernel/cpu/bugs.c
View File

@ -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);