885f82bfbc
The Speculative Store Bypass vulnerability can be mitigated with the Reduced Data Speculation (RDS) feature. To allow finer grained control of this eventually expensive mitigation a per task mitigation control is required. Add a new TIF_RDS flag and put it into the group of TIF flags which are evaluated for mismatch in switch_to(). If these bits differ in the previous and the next task, then the slow path function __switch_to_xtra() is invoked. Implement the TIF_RDS dependent mitigation control in the slow path. If the prctl for controlling Speculative Store Bypass is disabled or no task uses the prctl then there is no overhead in the switch_to() fast path. Update the KVM related speculation control functions to take TID_RDS into account as well. Based on a patch from Tim Chen. Completely rewritten. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
39 lines
1.1 KiB
C
39 lines
1.1 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _ASM_X86_SPECCTRL_H_
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#define _ASM_X86_SPECCTRL_H_
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#include <linux/thread_info.h>
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#include <asm/nospec-branch.h>
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/*
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* On VMENTER we must preserve whatever view of the SPEC_CTRL MSR
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* the guest has, while on VMEXIT we restore the host view. This
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* would be easier if SPEC_CTRL were architecturally maskable or
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* shadowable for guests but this is not (currently) the case.
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* Takes the guest view of SPEC_CTRL MSR as a parameter.
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*/
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extern void x86_spec_ctrl_set_guest(u64);
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extern void x86_spec_ctrl_restore_host(u64);
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/* AMD specific Speculative Store Bypass MSR data */
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extern u64 x86_amd_ls_cfg_base;
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extern u64 x86_amd_ls_cfg_rds_mask;
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/* The Intel SPEC CTRL MSR base value cache */
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extern u64 x86_spec_ctrl_base;
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static inline u64 rds_tif_to_spec_ctrl(u64 tifn)
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{
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BUILD_BUG_ON(TIF_RDS < SPEC_CTRL_RDS_SHIFT);
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return (tifn & _TIF_RDS) >> (TIF_RDS - SPEC_CTRL_RDS_SHIFT);
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}
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static inline u64 rds_tif_to_amd_ls_cfg(u64 tifn)
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{
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return (tifn & _TIF_RDS) ? x86_amd_ls_cfg_rds_mask : 0ULL;
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}
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extern void speculative_store_bypass_update(void);
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#endif
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