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irqchip/gic-v3: Support pseudo-NMIs when SCR_EL3.FIQ == 0 

The GIC's internal view of the priority mask register and the assigned
interrupt priorities are based on whether GIC security is enabled and
whether firmware routes Group 0 interrupts to EL3. At the moment, we
support priority masking when ICC_PMR_EL1 and interrupt priorities are
either both modified by the GIC, or both left unchanged.

Trusted Firmware-A's default interrupt routing model allows Group 0
interrupts to be delivered to the non-secure world (SCR_EL3.FIQ == 0).
Unfortunately, this is precisely the case that the GIC driver doesn't
support: ICC_PMR_EL1 remains unchanged, but the GIC's view of interrupt
priorities is different from the software programmed values.

Support pseudo-NMIs when SCR_EL3.FIQ == 0 by using a different value to
mask regular interrupts. All the other values remain the same.

Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20200912153707.667731-3-alexandru.elisei@arm.com
This commit is contained in:
Alexandru Elisei 2020-09-12 16:37:07 +01:00 committed by Marc Zyngier
parent 4e594ad106
commit 3367805909
4 changed files with 66 additions and 14 deletions
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8
arch/arm64/include/asm/arch_gicv3.h
View File

@ -153,7 +153,7 @@ static inline bool gic_prio_masking_enabled(void)
static inline void gic_pmr_mask_irqs(void)
{
BUILD_BUG_ON(GICD_INT_DEF_PRI < (GIC_PRIO_IRQOFF |
BUILD_BUG_ON(GICD_INT_DEF_PRI < (__GIC_PRIO_IRQOFF |
GIC_PRIO_PSR_I_SET));
BUILD_BUG_ON(GICD_INT_DEF_PRI >= GIC_PRIO_IRQON);
/*
@ -162,6 +162,12 @@ static inline void gic_pmr_mask_irqs(void)
* are applied to IRQ priorities
*/
BUILD_BUG_ON((0x80 | (GICD_INT_DEF_PRI >> 1)) >= GIC_PRIO_IRQON);
/*
* Same situation as above, but now we make sure that we can mask
* regular interrupts.
*/
BUILD_BUG_ON((0x80 | (GICD_INT_DEF_PRI >> 1)) < (__GIC_PRIO_IRQOFF_NS |
GIC_PRIO_PSR_I_SET));
gic_write_pmr(GIC_PRIO_IRQOFF);
}

14
arch/arm64/include/asm/ptrace.h
View File

@ -31,9 +31,21 @@
* interrupt disabling temporarily does not rely on IRQ priorities.
*/
#define GIC_PRIO_IRQON 0xe0
#define GIC_PRIO_IRQOFF (GIC_PRIO_IRQON & ~0x80)
#define __GIC_PRIO_IRQOFF (GIC_PRIO_IRQON & ~0x80)
#define __GIC_PRIO_IRQOFF_NS 0xa0
#define GIC_PRIO_PSR_I_SET (1 << 4)
#define GIC_PRIO_IRQOFF \
({ \
extern struct static_key_false gic_nonsecure_priorities;\
u8 __prio = __GIC_PRIO_IRQOFF; \
\
if (static_branch_unlikely(&gic_nonsecure_priorities)) \
__prio = __GIC_PRIO_IRQOFF_NS; \
\
__prio; \
})
/* Additional SPSR bits not exposed in the UABI */
#define PSR_MODE_THREAD_BIT (1 << 0)
#define PSR_IL_BIT (1 << 20)

2
arch/arm64/kernel/image-vars.h
View File

@ -101,6 +101,8 @@ KVM_NVHE_ALIAS(vgic_v3_cpuif_trap);
/* Static key checked in pmr_sync(). */
#ifdef CONFIG_ARM64_PSEUDO_NMI
KVM_NVHE_ALIAS(gic_pmr_sync);
/* Static key checked in GIC_PRIO_IRQOFF. */
KVM_NVHE_ALIAS(gic_nonsecure_priorities);
#endif
/* EL2 exception handling */

56
drivers/irqchip/irq-gic-v3.c
View File

@ -75,16 +75,14 @@ static DEFINE_STATIC_KEY_TRUE(supports_deactivate_key);
*
* If SCR_EL3.FIQ == 1, the values writen to/read from PMR and RPR at non-secure
* EL1 are subject to a similar operation thus matching the priorities presented
* from the (re)distributor when security is enabled.
* from the (re)distributor when security is enabled. When SCR_EL3.FIQ == 0,
* these values are unchanched by the GIC.
*
* see GICv3/GICv4 Architecture Specification (IHI0069D):
* - section 4.8.1 Non-secure accesses to register fields for Secure interrupt
* priorities.
* - Figure 4-7 Secure read of the priority field for a Non-secure Group 1
* interrupt.
*
* For now, we only support pseudo-NMIs if we have non-secure view of
* priorities.
*/
static DEFINE_STATIC_KEY_FALSE(supports_pseudo_nmis);
@ -97,6 +95,9 @@ static DEFINE_STATIC_KEY_FALSE(supports_pseudo_nmis);
DEFINE_STATIC_KEY_FALSE(gic_pmr_sync);
EXPORT_SYMBOL(gic_pmr_sync);
DEFINE_STATIC_KEY_FALSE(gic_nonsecure_priorities);
EXPORT_SYMBOL(gic_nonsecure_priorities);
/* ppi_nmi_refs[n] == number of cpus having ppi[n + 16] set as NMI */
static refcount_t *ppi_nmi_refs;
@ -932,14 +933,20 @@ static void gic_cpu_sys_reg_init(void)
/* Set priority mask register */
if (!gic_prio_masking_enabled()) {
write_gicreg(DEFAULT_PMR_VALUE, ICC_PMR_EL1);
} else {
} else if (gic_supports_nmi()) {
/*
* Mismatch configuration with boot CPU, the system is likely
* to die as interrupt masking will not work properly on all
* CPUs
*
* The boot CPU calls this function before enabling NMI support,
* and as a result we'll never see this warning in the boot path
* for that CPU.
*/
WARN_ON(gic_supports_nmi() && group0 &&
!gic_dist_security_disabled());
if (static_branch_unlikely(&gic_nonsecure_priorities))
WARN_ON(!group0 || gic_dist_security_disabled());
else
WARN_ON(group0 && !gic_dist_security_disabled());
}
/*
@ -1544,11 +1551,6 @@ static void gic_enable_nmi_support(void)
if (!gic_prio_masking_enabled())
return;
if (gic_has_group0() && !gic_dist_security_disabled()) {
pr_warn("SCR_EL3.FIQ is cleared, cannot enable use of pseudo-NMIs\n");
return;
}
ppi_nmi_refs = kcalloc(gic_data.ppi_nr, sizeof(*ppi_nmi_refs), GFP_KERNEL);
if (!ppi_nmi_refs)
return;
@ -1567,6 +1569,36 @@ static void gic_enable_nmi_support(void)
pr_info("Pseudo-NMIs enabled using %s ICC_PMR_EL1 synchronisation\n",
static_branch_unlikely(&gic_pmr_sync) ? "forced" : "relaxed");
/*
* How priority values are used by the GIC depends on two things:
* the security state of the GIC (controlled by the GICD_CTRL.DS bit)
* and if Group 0 interrupts can be delivered to Linux in the non-secure
* world as FIQs (controlled by the SCR_EL3.FIQ bit). These affect the
* the ICC_PMR_EL1 register and the priority that software assigns to
* interrupts:
*
* GICD_CTRL.DS | SCR_EL3.FIQ | ICC_PMR_EL1 | Group 1 priority
* -----------------------------------------------------------
* 1 | - | unchanged | unchanged
* -----------------------------------------------------------
* 0 | 1 | non-secure | non-secure
* -----------------------------------------------------------
* 0 | 0 | unchanged | non-secure
*
* where non-secure means that the value is right-shifted by one and the
* MSB bit set, to make it fit in the non-secure priority range.
*
* In the first two cases, where ICC_PMR_EL1 and the interrupt priority
* are both either modified or unchanged, we can use the same set of
* priorities.
*
* In the last case, where only the interrupt priorities are modified to
* be in the non-secure range, we use a different PMR value to mask IRQs
* and the rest of the values that we use remain unchanged.
*/
if (gic_has_group0() && !gic_dist_security_disabled())
static_branch_enable(&gic_nonsecure_priorities);
static_branch_enable(&supports_pseudo_nmis);
if (static_branch_likely(&supports_deactivate_key))