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x86/bugs/AMD: Add support to disable RDS on Fam[15,16,17]h if requested

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AMD does not need the Speculative Store Bypass mitigation to be enabled.

The parameters for this are already available and can be done via MSR
C001_1020. Each family uses a different bit in that MSR for this.

[ tglx: Expose the bit mask via a variable and move the actual MSR fiddling
  	into the bugs code as that's the right thing to do and also required
	to prepare for dynamic enable/disable ]

Suggested-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Konrad Rzeszutek Wilk 2018-04-25 22:04:24 -04:00 committed by Thomas Gleixner
parent 1115a859f3
commit 764f3c2158
5 changed files with 61 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
arch/x86/include/asm/cpufeatures.h
View File

@ -215,6 +215,7 @@
#define X86_FEATURE_USE_IBPB ( 7*32+21) /* "" Indirect Branch Prediction Barrier enabled */
#define X86_FEATURE_USE_IBRS_FW ( 7*32+22) /* "" Use IBRS during runtime firmware calls */
#define X86_FEATURE_SPEC_STORE_BYPASS_DISABLE ( 7*32+23) /* "" Disable Speculative Store Bypass. */
#define X86_FEATURE_AMD_RDS (7*32+24) /* "" AMD RDS implementation */
/* Virtualization flags: Linux defined, word 8 */
#define X86_FEATURE_TPR_SHADOW ( 8*32+ 0) /* Intel TPR Shadow */

4
arch/x86/include/asm/nospec-branch.h
View File

@ -244,6 +244,10 @@ enum ssb_mitigation {
SPEC_STORE_BYPASS_DISABLE,
};
/* AMD specific Speculative Store Bypass MSR data */
extern u64 x86_amd_ls_cfg_base;
extern u64 x86_amd_ls_cfg_rds_mask;
extern char __indirect_thunk_start[];
extern char __indirect_thunk_end[];

26
arch/x86/kernel/cpu/amd.c
View File

@ -10,6 +10,7 @@
#include <asm/processor.h>
#include <asm/apic.h>
#include <asm/cpu.h>
#include <asm/nospec-branch.h>
#include <asm/smp.h>
#include <asm/pci-direct.h>
#include <asm/delay.h>
@ -554,6 +555,26 @@ static void bsp_init_amd(struct cpuinfo_x86 *c)
rdmsrl(MSR_FAM10H_NODE_ID, value);
nodes_per_socket = ((value >> 3) & 7) + 1;
}
if (c->x86 >= 0x15 && c->x86 <= 0x17) {
unsigned int bit;
switch (c->x86) {
case 0x15: bit = 54; break;
case 0x16: bit = 33; break;
case 0x17: bit = 10; break;
default: return;
}
/*
* Try to cache the base value so further operations can
* avoid RMW. If that faults, do not enable RDS.
*/
if (!rdmsrl_safe(MSR_AMD64_LS_CFG, &x86_amd_ls_cfg_base)) {
setup_force_cpu_cap(X86_FEATURE_RDS);
setup_force_cpu_cap(X86_FEATURE_AMD_RDS);
x86_amd_ls_cfg_rds_mask = 1ULL << bit;
}
}
}
static void early_detect_mem_encrypt(struct cpuinfo_x86 *c)
@ -898,6 +919,11 @@ static void init_amd(struct cpuinfo_x86 *c)
/* AMD CPUs don't reset SS attributes on SYSRET, Xen does. */
if (!cpu_has(c, X86_FEATURE_XENPV))
set_cpu_bug(c, X86_BUG_SYSRET_SS_ATTRS);
if (boot_cpu_has(X86_FEATURE_AMD_RDS)) {
set_cpu_cap(c, X86_FEATURE_RDS);
set_cpu_cap(c, X86_FEATURE_AMD_RDS);
}
}
#ifdef CONFIG_X86_32

27
arch/x86/kernel/cpu/bugs.c
View File

@ -41,6 +41,13 @@ static u64 __ro_after_init x86_spec_ctrl_base;
*/
static u64 __ro_after_init x86_spec_ctrl_mask = ~SPEC_CTRL_IBRS;
/*
* AMD specific MSR info for Speculative Store Bypass control.
* x86_amd_ls_cfg_rds_mask is initialized in identify_boot_cpu().
*/
u64 __ro_after_init x86_amd_ls_cfg_base;
u64 __ro_after_init x86_amd_ls_cfg_rds_mask;
void __init check_bugs(void)
{
identify_boot_cpu();
@ -52,7 +59,8 @@ void __init check_bugs(void)
/*
* Read the SPEC_CTRL MSR to account for reserved bits which may
* have unknown values.
* have unknown values. AMD64_LS_CFG MSR is cached in the early AMD
* init code as it is not enumerated and depends on the family.
*/
if (boot_cpu_has(X86_FEATURE_IBRS))
rdmsrl(MSR_IA32_SPEC_CTRL, x86_spec_ctrl_base);
@ -154,6 +162,14 @@ void x86_spec_ctrl_restore_host(u64 guest_spec_ctrl)
}
EXPORT_SYMBOL_GPL(x86_spec_ctrl_restore_host);
static void x86_amd_rds_enable(void)
{
u64 msrval = x86_amd_ls_cfg_base | x86_amd_ls_cfg_rds_mask;
if (boot_cpu_has(X86_FEATURE_AMD_RDS))
wrmsrl(MSR_AMD64_LS_CFG, msrval);
}
#ifdef RETPOLINE
static bool spectre_v2_bad_module;
@ -443,6 +459,11 @@ static enum ssb_mitigation_cmd __init __ssb_select_mitigation(void)
switch (cmd) {
case SPEC_STORE_BYPASS_CMD_AUTO:
/*
* AMD platforms by default don't need SSB mitigation.
*/
if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD)
break;
case SPEC_STORE_BYPASS_CMD_ON:
mode = SPEC_STORE_BYPASS_DISABLE;
break;
@ -469,6 +490,7 @@ static enum ssb_mitigation_cmd __init __ssb_select_mitigation(void)
x86_spec_ctrl_set(SPEC_CTRL_RDS);
break;
case X86_VENDOR_AMD:
x86_amd_rds_enable();
break;
}
}
@ -490,6 +512,9 @@ void x86_spec_ctrl_setup_ap(void)
{
if (boot_cpu_has(X86_FEATURE_IBRS))
x86_spec_ctrl_set(x86_spec_ctrl_base & ~x86_spec_ctrl_mask);
if (ssb_mode == SPEC_STORE_BYPASS_DISABLE)
x86_amd_rds_enable();
}
#ifdef CONFIG_SYSFS

4
arch/x86/kernel/cpu/common.c
View File

@ -943,6 +943,10 @@ static const __initconst struct x86_cpu_id cpu_no_spec_store_bypass[] = {
{ X86_VENDOR_CENTAUR, 5, },
{ X86_VENDOR_INTEL, 5, },
{ X86_VENDOR_NSC, 5, },
{ X86_VENDOR_AMD, 0x12, },
{ X86_VENDOR_AMD, 0x11, },
{ X86_VENDOR_AMD, 0x10, },
{ X86_VENDOR_AMD, 0xf, },
{ X86_VENDOR_ANY, 4, },
{}
};