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KVM: arm64: Add templates for BHB mitigation sequences

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KVM writes the Spectre-v2 mitigation template at the beginning of each
vector when a CPU requires a specific sequence to run.
Because the template is copied, it can not be modified by the alternatives
at runtime. As the KVM template code is intertwined with the bp-hardening
callbacks all templates must have a bp-hardening callback.
Add templates for calling ARCH_WORKAROUND_3  and one for each value of K
in the brancy-loop. Identify these sequences by a new parameter
template_start, and add a copy of install_bp_hardening_cb() that is able to
install them.

Change-Id: I3dbb2d1e06663cbf39b1d212547ac64d569fd72e
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Git-commit: a68912a3ae
Git-repo: https://android.googlesource.com/kernel/common/
Signed-off-by: Kishor Krishna Bhat <quic_kishkris@quicinc.com>
This commit is contained in:
James Morse
2022-09-07 16:25:42 +05:30
committed by Gerrit - the friendly Code Review server
parent 60d1e2d44c
commit b0264309e1
5 changed files with 130 additions and 3 deletions
Download Patch File Download Diff File Expand all files Collapse all files

65
arch/arm64/kernel/cpu_errata.c
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@@ -98,6 +98,14 @@ DEFINE_PER_CPU_READ_MOSTLY(struct bp_hardening_data, bp_hardening_data);
#ifdef CONFIG_KVM_INDIRECT_VECTORS
extern char __smccc_workaround_1_smc_start[];
extern char __smccc_workaround_1_smc_end[];
extern char __smccc_workaround_3_smc_start[];
extern char __smccc_workaround_3_smc_end[];
extern char __spectre_bhb_loop_k8_start[];
extern char __spectre_bhb_loop_k8_end[];
extern char __spectre_bhb_loop_k24_start[];
extern char __spectre_bhb_loop_k24_end[];
extern char __spectre_bhb_loop_k32_start[];
extern char __spectre_bhb_loop_k32_end[];
static void __copy_hyp_vect_bpi(int slot, const char *hyp_vecs_start,
const char *hyp_vecs_end)
@@ -111,11 +119,11 @@ static void __copy_hyp_vect_bpi(int slot, const char *hyp_vecs_start,
__flush_icache_range((uintptr_t)dst, (uintptr_t)dst + SZ_2K);
}
static DEFINE_SPINLOCK(bp_lock);
static void install_bp_hardening_cb(bp_hardening_cb_t fn,
const char *hyp_vecs_start,
const char *hyp_vecs_end)
{
static DEFINE_SPINLOCK(bp_lock);
int cpu, slot = -1;
spin_lock(&bp_lock);
@@ -134,6 +142,7 @@ static void install_bp_hardening_cb(bp_hardening_cb_t fn,
__this_cpu_write(bp_hardening_data.hyp_vectors_slot, slot);
__this_cpu_write(bp_hardening_data.fn, fn);
__this_cpu_write(bp_hardening_data.template_start, hyp_vecs_start);
spin_unlock(&bp_lock);
}
#else
@@ -982,6 +991,60 @@ enum mitigation_state arm64_get_spectre_bhb_state(void)
return spectre_bhb_state;
}
#ifdef CONFIG_KVM_INDIRECT_VECTORS
static const char *kvm_bhb_get_vecs_end(const char *start)
{
if (start == __smccc_workaround_3_smc_start)
return __smccc_workaround_3_smc_end;
else if (start == __spectre_bhb_loop_k8_start)
return __spectre_bhb_loop_k8_end;
else if (start == __spectre_bhb_loop_k24_start)
return __spectre_bhb_loop_k24_end;
else if (start == __spectre_bhb_loop_k32_start)
return __spectre_bhb_loop_k32_end;
return NULL;
void kvm_setup_bhb_slot(const char *hyp_vecs_start)
{
int cpu, slot = -1;
const char *hyp_vecs_end;
if (!IS_ENABLED(CONFIG_KVM) || !is_hyp_mode_available())
return;
hyp_vecs_end = kvm_bhb_get_vecs_end(hyp_vecs_start);
if (WARN_ON_ONCE(!hyp_vecs_start || !hyp_vecs_end))
return;
spin_lock(&bp_lock);
for_each_possible_cpu(cpu) {
if (per_cpu(bp_hardening_data.template_start, cpu) == hyp_vecs_start) {
slot = per_cpu(bp_hardening_data.hyp_vectors_slot, cpu);
break;
}
}
if (slot == -1) {
slot = atomic_inc_return(&arm64_el2_vector_last_slot);
BUG_ON(slot >= BP_HARDEN_EL2_SLOTS);
__copy_hyp_vect_bpi(slot, hyp_vecs_start, hyp_vecs_end);
}
__this_cpu_write(bp_hardening_data.hyp_vectors_slot, slot);
__this_cpu_write(bp_hardening_data.template_start, hyp_vecs_start);
spin_unlock(&bp_lock);
}
#else
#define __smccc_workaround_3_smc_start NULL
#define __spectre_bhb_loop_k8_start NULL
#define __spectre_bhb_loop_k24_start NULL
#define __spectre_bhb_loop_k32_start NULL
void kvm_setup_bhb_slot(const char *hyp_vecs_start) { };
#endif
ssize_t cpu_show_spec_store_bypass(struct device *dev,
struct device_attribute *attr, char *buf)
{