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Merge branch kvm-arm64/oslock into kvmarm-master/next

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* kvm-arm64/oslock:
  : .
  : Debug OS-Lock emulation courtesy of Oliver Upton. From the cover letter:
  :
  : "KVM does not implement the debug architecture to the letter of the
  : specification. One such issue is the fact that KVM treats the OS Lock as
  : RAZ/WI, rather than emulating its behavior on hardware. This series adds
  : emulation support for the OS Lock to KVM. Emulation is warranted as the
  : OS Lock affects debug exceptions taken from all ELs, and is not limited
  : to only the context of the guest."
  : .
  selftests: KVM: Test OS lock behavior
  selftests: KVM: Add OSLSR_EL1 to the list of blessed regs
  KVM: arm64: Emulate the OS Lock
  KVM: arm64: Allow guest to set the OSLK bit
  KVM: arm64: Stash OSLSR_EL1 in the cpu context
  KVM: arm64: Correctly treat writes to OSLSR_EL1 as undefined

Signed-off-by: Marc Zyngier <maz@kernel.org>
This commit is contained in:
Marc Zyngier 2022-02-08 14:26:30 +00:00
commit b61fa004a4
6 changed files with 149 additions and 23 deletions
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5
arch/arm64/include/asm/kvm_host.h
View File

@ -171,6 +171,7 @@ enum vcpu_sysreg {
PAR_EL1, /* Physical Address Register */
MDSCR_EL1, /* Monitor Debug System Control Register */
MDCCINT_EL1, /* Monitor Debug Comms Channel Interrupt Enable Reg */
OSLSR_EL1, /* OS Lock Status Register */
DISR_EL1, /* Deferred Interrupt Status Register */
/* Performance Monitors Registers */
@ -725,6 +726,10 @@ void kvm_arm_vcpu_init_debug(struct kvm_vcpu *vcpu);
void kvm_arm_setup_debug(struct kvm_vcpu *vcpu);
void kvm_arm_clear_debug(struct kvm_vcpu *vcpu);
void kvm_arm_reset_debug_ptr(struct kvm_vcpu *vcpu);
#define kvm_vcpu_os_lock_enabled(vcpu) \
(!!(__vcpu_sys_reg(vcpu, OSLSR_EL1) & SYS_OSLSR_OSLK))
int kvm_arm_vcpu_arch_set_attr(struct kvm_vcpu *vcpu,
struct kvm_device_attr *attr);
int kvm_arm_vcpu_arch_get_attr(struct kvm_vcpu *vcpu,

8
arch/arm64/include/asm/sysreg.h
View File

@ -128,8 +128,16 @@
#define SYS_DBGWVRn_EL1(n) sys_reg(2, 0, 0, n, 6)
#define SYS_DBGWCRn_EL1(n) sys_reg(2, 0, 0, n, 7)
#define SYS_MDRAR_EL1 sys_reg(2, 0, 1, 0, 0)
#define SYS_OSLAR_EL1 sys_reg(2, 0, 1, 0, 4)
#define SYS_OSLAR_OSLK BIT(0)
#define SYS_OSLSR_EL1 sys_reg(2, 0, 1, 1, 4)
#define SYS_OSLSR_OSLM_MASK (BIT(3) | BIT(0))
#define SYS_OSLSR_OSLM_NI 0
#define SYS_OSLSR_OSLM_IMPLEMENTED BIT(3)
#define SYS_OSLSR_OSLK BIT(1)
#define SYS_OSDLR_EL1 sys_reg(2, 0, 1, 3, 4)
#define SYS_DBGPRCR_EL1 sys_reg(2, 0, 1, 4, 4)
#define SYS_DBGCLAIMSET_EL1 sys_reg(2, 0, 7, 8, 6)

26
arch/arm64/kvm/debug.c
View File

@ -105,9 +105,11 @@ static void kvm_arm_setup_mdcr_el2(struct kvm_vcpu *vcpu)
* - Userspace is using the hardware to debug the guest
* (KVM_GUESTDBG_USE_HW is set).
* - The guest is not using debug (KVM_ARM64_DEBUG_DIRTY is clear).
* - The guest has enabled the OS Lock (debug exceptions are blocked).
*/
if ((vcpu->guest_debug & KVM_GUESTDBG_USE_HW) ||
!(vcpu->arch.flags & KVM_ARM64_DEBUG_DIRTY))
!(vcpu->arch.flags & KVM_ARM64_DEBUG_DIRTY) ||
kvm_vcpu_os_lock_enabled(vcpu))
vcpu->arch.mdcr_el2 |= MDCR_EL2_TDA;
trace_kvm_arm_set_dreg32("MDCR_EL2", vcpu->arch.mdcr_el2);
@ -160,8 +162,8 @@ void kvm_arm_setup_debug(struct kvm_vcpu *vcpu)
kvm_arm_setup_mdcr_el2(vcpu);
/* Is Guest debugging in effect? */
if (vcpu->guest_debug) {
/* Check if we need to use the debug registers. */
if (vcpu->guest_debug || kvm_vcpu_os_lock_enabled(vcpu)) {
/* Save guest debug state */
save_guest_debug_regs(vcpu);
@ -223,6 +225,19 @@ void kvm_arm_setup_debug(struct kvm_vcpu *vcpu)
trace_kvm_arm_set_regset("WAPTS", get_num_wrps(),
&vcpu->arch.debug_ptr->dbg_wcr[0],
&vcpu->arch.debug_ptr->dbg_wvr[0]);
/*
* The OS Lock blocks debug exceptions in all ELs when it is
* enabled. If the guest has enabled the OS Lock, constrain its
* effects to the guest. Emulate the behavior by clearing
* MDSCR_EL1.MDE. In so doing, we ensure that host debug
* exceptions are unaffected by guest configuration of the OS
* Lock.
*/
} else if (kvm_vcpu_os_lock_enabled(vcpu)) {
mdscr = vcpu_read_sys_reg(vcpu, MDSCR_EL1);
mdscr &= ~DBG_MDSCR_MDE;
vcpu_write_sys_reg(vcpu, mdscr, MDSCR_EL1);
}
}
@ -244,7 +259,10 @@ void kvm_arm_clear_debug(struct kvm_vcpu *vcpu)
{
trace_kvm_arm_clear_debug(vcpu->guest_debug);
if (vcpu->guest_debug) {
/*
* Restore the guest's debug registers if we were using them.
*/
if (vcpu->guest_debug || kvm_vcpu_os_lock_enabled(vcpu)) {
restore_guest_debug_regs(vcpu);
/*

74
arch/arm64/kvm/sys_regs.c
View File

@ -44,6 +44,10 @@
* 64bit interface.
*/
static int reg_from_user(u64 *val, const void __user *uaddr, u64 id);
static int reg_to_user(void __user *uaddr, const u64 *val, u64 id);
static u64 sys_reg_to_index(const struct sys_reg_desc *reg);
static bool read_from_write_only(struct kvm_vcpu *vcpu,
struct sys_reg_params *params,
const struct sys_reg_desc *r)
@ -287,16 +291,55 @@ static bool trap_loregion(struct kvm_vcpu *vcpu,
return trap_raz_wi(vcpu, p, r);
}
static bool trap_oslar_el1(struct kvm_vcpu *vcpu,
struct sys_reg_params *p,
const struct sys_reg_desc *r)
{
u64 oslsr;
if (!p->is_write)
return read_from_write_only(vcpu, p, r);
/* Forward the OSLK bit to OSLSR */
oslsr = __vcpu_sys_reg(vcpu, OSLSR_EL1) & ~SYS_OSLSR_OSLK;
if (p->regval & SYS_OSLAR_OSLK)
oslsr |= SYS_OSLSR_OSLK;
__vcpu_sys_reg(vcpu, OSLSR_EL1) = oslsr;
return true;
}
static bool trap_oslsr_el1(struct kvm_vcpu *vcpu,
struct sys_reg_params *p,
const struct sys_reg_desc *r)
{
if (p->is_write) {
return ignore_write(vcpu, p);
} else {
p->regval = (1 << 3);
return true;
}
if (p->is_write)
return write_to_read_only(vcpu, p, r);
p->regval = __vcpu_sys_reg(vcpu, r->reg);
return true;
}
static int set_oslsr_el1(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
const struct kvm_one_reg *reg, void __user *uaddr)
{
u64 id = sys_reg_to_index(rd);
u64 val;
int err;
err = reg_from_user(&val, uaddr, id);
if (err)
return err;
/*
* The only modifiable bit is the OSLK bit. Refuse the write if
* userspace attempts to change any other bit in the register.
*/
if ((val ^ rd->val) & ~SYS_OSLSR_OSLK)
return -EINVAL;
__vcpu_sys_reg(vcpu, rd->reg) = val;
return 0;
}
static bool trap_dbgauthstatus_el1(struct kvm_vcpu *vcpu,
@ -1164,10 +1207,6 @@ static bool access_raz_id_reg(struct kvm_vcpu *vcpu,
return __access_id_reg(vcpu, p, r, true);
}
static int reg_from_user(u64 *val, const void __user *uaddr, u64 id);
static int reg_to_user(void __user *uaddr, const u64 *val, u64 id);
static u64 sys_reg_to_index(const struct sys_reg_desc *reg);
/* Visibility overrides for SVE-specific control registers */
static unsigned int sve_visibility(const struct kvm_vcpu *vcpu,
const struct sys_reg_desc *rd)
@ -1418,9 +1457,9 @@ static unsigned int mte_visibility(const struct kvm_vcpu *vcpu,
* Debug handling: We do trap most, if not all debug related system
* registers. The implementation is good enough to ensure that a guest
* can use these with minimal performance degradation. The drawback is
* that we don't implement any of the external debug, none of the
* OSlock protocol. This should be revisited if we ever encounter a
* more demanding guest...
* that we don't implement any of the external debug architecture.
* This should be revisited if we ever encounter a more demanding
* guest...
*/
static const struct sys_reg_desc sys_reg_descs[] = {
{ SYS_DESC(SYS_DC_ISW), access_dcsw },
@ -1447,8 +1486,9 @@ static const struct sys_reg_desc sys_reg_descs[] = {
DBG_BCR_BVR_WCR_WVR_EL1(15),
{ SYS_DESC(SYS_MDRAR_EL1), trap_raz_wi },
{ SYS_DESC(SYS_OSLAR_EL1), trap_raz_wi },
{ SYS_DESC(SYS_OSLSR_EL1), trap_oslsr_el1 },
{ SYS_DESC(SYS_OSLAR_EL1), trap_oslar_el1 },
{ SYS_DESC(SYS_OSLSR_EL1), trap_oslsr_el1, reset_val, OSLSR_EL1,
SYS_OSLSR_OSLM_IMPLEMENTED, .set_user = set_oslsr_el1, },
{ SYS_DESC(SYS_OSDLR_EL1), trap_raz_wi },
{ SYS_DESC(SYS_DBGPRCR_EL1), trap_raz_wi },
{ SYS_DESC(SYS_DBGCLAIMSET_EL1), trap_raz_wi },
@ -1920,10 +1960,10 @@ static const struct sys_reg_desc cp14_regs[] = {
DBGBXVR(0),
/* DBGOSLAR */
{ Op1( 0), CRn( 1), CRm( 0), Op2( 4), trap_raz_wi },
{ Op1( 0), CRn( 1), CRm( 0), Op2( 4), trap_oslar_el1 },
DBGBXVR(1),
/* DBGOSLSR */
{ Op1( 0), CRn( 1), CRm( 1), Op2( 4), trap_oslsr_el1 },
{ Op1( 0), CRn( 1), CRm( 1), Op2( 4), trap_oslsr_el1, NULL, OSLSR_EL1 },
DBGBXVR(2),
DBGBXVR(3),
/* DBGOSDLR */

58
tools/testing/selftests/kvm/aarch64/debug-exceptions.c
View File

@ -23,7 +23,7 @@
#define SPSR_D (1 << 9)
#define SPSR_SS (1 << 21)
extern unsigned char sw_bp, hw_bp, bp_svc, bp_brk, hw_wp, ss_start;
extern unsigned char sw_bp, sw_bp2, hw_bp, hw_bp2, bp_svc, bp_brk, hw_wp, ss_start;
static volatile uint64_t sw_bp_addr, hw_bp_addr;
static volatile uint64_t wp_addr, wp_data_addr;
static volatile uint64_t svc_addr;
@ -47,6 +47,14 @@ static void reset_debug_state(void)
isb();
}
static void enable_os_lock(void)
{
write_sysreg(1, oslar_el1);
isb();
GUEST_ASSERT(read_sysreg(oslsr_el1) & 2);
}
static void install_wp(uint64_t addr)
{
uint32_t wcr;
@ -99,6 +107,7 @@ static void guest_code(void)
GUEST_SYNC(0);
/* Software-breakpoint */
reset_debug_state();
asm volatile("sw_bp: brk #0");
GUEST_ASSERT_EQ(sw_bp_addr, PC(sw_bp));
@ -152,6 +161,51 @@ static void guest_code(void)
GUEST_ASSERT_EQ(ss_addr[1], PC(ss_start) + 4);
GUEST_ASSERT_EQ(ss_addr[2], PC(ss_start) + 8);
GUEST_SYNC(6);
/* OS Lock does not block software-breakpoint */
reset_debug_state();
enable_os_lock();
sw_bp_addr = 0;
asm volatile("sw_bp2: brk #0");
GUEST_ASSERT_EQ(sw_bp_addr, PC(sw_bp2));
GUEST_SYNC(7);
/* OS Lock blocking hardware-breakpoint */
reset_debug_state();
enable_os_lock();
install_hw_bp(PC(hw_bp2));
hw_bp_addr = 0;
asm volatile("hw_bp2: nop");
GUEST_ASSERT_EQ(hw_bp_addr, 0);
GUEST_SYNC(8);
/* OS Lock blocking watchpoint */
reset_debug_state();
enable_os_lock();
write_data = '\0';
wp_data_addr = 0;
install_wp(PC(write_data));
write_data = 'x';
GUEST_ASSERT_EQ(write_data, 'x');
GUEST_ASSERT_EQ(wp_data_addr, 0);
GUEST_SYNC(9);
/* OS Lock blocking single-step */
reset_debug_state();
enable_os_lock();
ss_addr[0] = 0;
install_ss();
ss_idx = 0;
asm volatile("mrs x0, esr_el1\n\t"
"add x0, x0, #1\n\t"
"msr daifset, #8\n\t"
: : : "x0");
GUEST_ASSERT_EQ(ss_addr[0], 0);
GUEST_DONE();
}
@ -223,7 +277,7 @@ int main(int argc, char *argv[])
vm_install_sync_handler(vm, VECTOR_SYNC_CURRENT,
ESR_EC_SVC64, guest_svc_handler);
for (stage = 0; stage < 7; stage++) {
for (stage = 0; stage < 11; stage++) {
vcpu_run(vm, VCPU_ID);
switch (get_ucall(vm, VCPU_ID, &uc)) {

1
tools/testing/selftests/kvm/aarch64/get-reg-list.c
View File

@ -760,6 +760,7 @@ static __u64 base_regs[] = {
ARM64_SYS_REG(2, 0, 0, 15, 5),
ARM64_SYS_REG(2, 0, 0, 15, 6),
ARM64_SYS_REG(2, 0, 0, 15, 7),
ARM64_SYS_REG(2, 0, 1, 1, 4), /* OSLSR_EL1 */
ARM64_SYS_REG(2, 4, 0, 7, 0), /* DBGVCR32_EL2 */
ARM64_SYS_REG(3, 0, 0, 0, 5), /* MPIDR_EL1 */
ARM64_SYS_REG(3, 0, 0, 1, 0), /* ID_PFR0_EL1 */