On 8 July 2014 13:21, Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> wrote:
> According to section 7.1 of the UEFI spec, Runtime Services are not fully
> reentrant, and there are particular combinations of calls that need to be
> serialized.
>
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
> ---
>
> So this is v2 of the UEFI Runtime Services serialization patch: this time, I use
> a single spinlock rather than a set of mutexes, resulting in all services to be
> serialized with respect to all others. Also added handling of NMI state, as this
> results in some of the restrictions being lifted (x86, ia64 only)
>
> One question remains: with the NMI deadlock handling in place, is it really
> necessary to disable interrupts in all cases?
>
I omitted this hunk from the patch by accident:
diff --git a/arch/x86/include/asm/efi.h b/arch/x86/include/asm/efi.h
index 55059a50a01f..d8ee5bb527e5 100644
--- a/arch/x86/include/asm/efi.h
+++ b/arch/x86/include/asm/efi.h
@@ -2,6 +2,7 @@
#define _ASM_X86_EFI_H
#include <asm/i387.h>
+#include <asm/nmi.h>
/*
* We map the EFI regions needed for runtime services non-contiguously,
* with preserved alignment on virtual addresses starting from -4G down
@@ -52,6 +53,8 @@ extern unsigned long asmlinkage efi_call_phys(void *, ...);
kernel_fpu_end(); \
})
+#define efi_in_nmi() in_nmi()
+
#define efi_ioremap(addr, size, type, attr) ioremap_cache(addr, size)
#else /* !CONFIG_X86_32 */
> drivers/firmware/efi/runtime-wrappers.c | 167 +++++++++++++++++++++++++++++---
> 1 file changed, 155 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/firmware/efi/runtime-wrappers.c b/drivers/firmware/efi/runtime-wrappers.c
> index 10daa4bbb258..5ee3b16498a2 100644
> --- a/drivers/firmware/efi/runtime-wrappers.c
> +++ b/drivers/firmware/efi/runtime-wrappers.c
> @@ -14,11 +14,76 @@
> * This file is released under the GPLv2.
> */
>
> +#include <linux/bug.h>
> #include <linux/efi.h>
> -#include <linux/spinlock.h> /* spinlock_t */
> +#include <linux/mutex.h>
> +#include <linux/spinlock.h>
> #include <asm/efi.h>
>
> /*
> + * According to section 7.1 of the UEFI spec, Runtime Services are not fully
> + * reentrant, and there are particular combinations of calls that need to be
> + * serialized.
> + *
> + * Table 31. Rules for Reentry Into Runtime Services
> + * +------------------------------------+-------------------------------+
> + * | If previous call is busy in | Forbidden to call |
> + * +------------------------------------+-------------------------------+
> + * | Any | SetVirtualAddressMap() |
> + * +------------------------------------+-------------------------------+
> + * | ConvertPointer() | ConvertPointer() |
> + * +------------------------------------+-------------------------------+
> + * | SetVariable() | ResetSystem() |
> + * | UpdateCapsule() | |
> + * | SetTime() | |
> + * | SetWakeupTime() | |
> + * | GetNextHighMonotonicCount() | |
> + * +------------------------------------+-------------------------------+
> + * | GetVariable() | GetVariable() |
> + * | GetNextVariableName() | GetNextVariableName() |
> + * | SetVariable() | SetVariable() |
> + * | QueryVariableInfo() | QueryVariableInfo() |
> + * | UpdateCapsule() | UpdateCapsule() |
> + * | QueryCapsuleCapabilities() | QueryCapsuleCapabilities() |
> + * | GetNextHighMonotonicCount() | GetNextHighMonotonicCount() |
> + * +------------------------------------+-------------------------------+
> + * | GetTime() | GetTime() |
> + * | SetTime() | SetTime() |
> + * | GetWakeupTime() | GetWakeupTime() |
> + * | SetWakeupTime() | SetWakeupTime() |
> + * +------------------------------------+-------------------------------+
> + *
> + * Instead of adding locks for each of the groups, we add a single spinlock
> + * that serializes all runtime services calls with respect to all others.
> + */
> +static DEFINE_SPINLOCK(efi_runtime_lock);
> +
> +/*
> + * Some runtime services calls can be reentrant under NMI, even if the table
> + * above says they are not.
> + *
> + * Table 32. Functions that may be called after Machine Check ,INIT and NMI
> + * +----------------------------+------------------------------------------+
> + * | Function | Called after Machine Check, INIT and NMI |
> + * +----------------------------+------------------------------------------+
> + * | GetTime() | Yes, even if previously busy. |
> + * | GetVariable() | Yes, even if previously busy |
> + * | GetNextVariableName() | Yes, even if previously busy |
> + * | QueryVariableInfo() | Yes, even if previously busy |
> + * | SetVariable() | Yes, even if previously busy |
> + * | UpdateCapsule() | Yes, even if previously busy |
> + * | QueryCapsuleCapabilities() | Yes, even if previously busy |
> + * | ResetSystem() | Yes, even if previously busy |
> + * +----------------------------+------------------------------------------+
> + *
> + * In order to prevent deadlocks under NMI, the wrappers for these functions
> + * only grab the efi_runtime_lock or rtc_lock spinlocks if !efi_in_nmi().
> + */
> +#ifndef efi_in_nmi
> +#define efi_in_nmi() (0)
> +#endif
> +
> +/*
> * As per commit ef68c8f87ed1 ("x86: Serialize EFI time accesses on rtc_lock"),
> * the EFI specification requires that callers of the time related runtime
> * functions serialize with other CMOS accesses in the kernel, as the EFI time
> @@ -31,9 +96,15 @@ static efi_status_t virt_efi_get_time(efi_time_t *tm, efi_time_cap_t *tc)
> unsigned long flags;
> efi_status_t status;
>
> - spin_lock_irqsave(&rtc_lock, flags);
> + if (!efi_in_nmi()) {
> + spin_lock_irqsave(&rtc_lock, flags);
> + spin_lock(&efi_runtime_lock);
> + }
> status = efi_call_virt(get_time, tm, tc);
> - spin_unlock_irqrestore(&rtc_lock, flags);
> + if (!efi_in_nmi()) {
> + spin_unlock(&efi_runtime_lock);
> + spin_unlock_irqrestore(&rtc_lock, flags);
> + }
> return status;
> }
>
> @@ -42,8 +113,11 @@ static efi_status_t virt_efi_set_time(efi_time_t *tm)
> unsigned long flags;
> efi_status_t status;
>
> + BUG_ON(efi_in_nmi());
> spin_lock_irqsave(&rtc_lock, flags);
> + spin_lock(&efi_runtime_lock);
> status = efi_call_virt(set_time, tm);
> + spin_unlock(&efi_runtime_lock);
> spin_unlock_irqrestore(&rtc_lock, flags);
> return status;
> }
> @@ -55,8 +129,11 @@ static efi_status_t virt_efi_get_wakeup_time(efi_bool_t *enabled,
> unsigned long flags;
> efi_status_t status;
>
> + BUG_ON(efi_in_nmi());
> spin_lock_irqsave(&rtc_lock, flags);
> + spin_lock(&efi_runtime_lock);
> status = efi_call_virt(get_wakeup_time, enabled, pending, tm);
> + spin_unlock(&efi_runtime_lock);
> spin_unlock_irqrestore(&rtc_lock, flags);
> return status;
> }
> @@ -66,8 +143,11 @@ static efi_status_t virt_efi_set_wakeup_time(efi_bool_t enabled, efi_time_t *tm)
> unsigned long flags;
> efi_status_t status;
>
> + BUG_ON(efi_in_nmi());
> spin_lock_irqsave(&rtc_lock, flags);
> + spin_lock(&efi_runtime_lock);
> status = efi_call_virt(set_wakeup_time, enabled, tm);
> + spin_unlock(&efi_runtime_lock);
> spin_unlock_irqrestore(&rtc_lock, flags);
> return status;
> }
> @@ -78,14 +158,31 @@ static efi_status_t virt_efi_get_variable(efi_char16_t *name,
> unsigned long *data_size,
> void *data)
> {
> - return efi_call_virt(get_variable, name, vendor, attr, data_size, data);
> + unsigned long flags;
> + efi_status_t status;
> +
> + if (!efi_in_nmi())
> + spin_lock_irqsave(&efi_runtime_lock, flags);
> + status = efi_call_virt(get_variable, name, vendor, attr, data_size,
> + data);
> + if (!efi_in_nmi())
> + spin_unlock_irqrestore(&efi_runtime_lock, flags);
> + return status;
> }
>
> static efi_status_t virt_efi_get_next_variable(unsigned long *name_size,
> efi_char16_t *name,
> efi_guid_t *vendor)
> {
> - return efi_call_virt(get_next_variable, name_size, name, vendor);
> + unsigned long flags;
> + efi_status_t status;
> +
> + if (!efi_in_nmi())
> + spin_lock_irqsave(&efi_runtime_lock, flags);
> + status = efi_call_virt(get_next_variable, name_size, name, vendor);
> + if (!efi_in_nmi())
> + spin_unlock_irqrestore(&efi_runtime_lock, flags);
> + return status;
> }
>
> static efi_status_t virt_efi_set_variable(efi_char16_t *name,
> @@ -94,7 +191,16 @@ static efi_status_t virt_efi_set_variable(efi_char16_t *name,
> unsigned long data_size,
> void *data)
> {
> - return efi_call_virt(set_variable, name, vendor, attr, data_size, data);
> + unsigned long flags;
> + efi_status_t status;
> +
> + if (!efi_in_nmi())
> + spin_lock_irqsave(&efi_runtime_lock, flags);
> + status = efi_call_virt(set_variable, name, vendor, attr, data_size,
> + data);
> + if (!efi_in_nmi())
> + spin_unlock_irqrestore(&efi_runtime_lock, flags);
> + return status;
> }
>
> static efi_status_t virt_efi_query_variable_info(u32 attr,
> @@ -102,16 +208,31 @@ static efi_status_t virt_efi_query_variable_info(u32 attr,
> u64 *remaining_space,
> u64 *max_variable_size)
> {
> + unsigned long flags;
> + efi_status_t status;
> +
> if (efi.runtime_version < EFI_2_00_SYSTEM_TABLE_REVISION)
> return EFI_UNSUPPORTED;
>
> - return efi_call_virt(query_variable_info, attr, storage_space,
> - remaining_space, max_variable_size);
> + if (!efi_in_nmi())
> + spin_lock_irqsave(&efi_runtime_lock, flags);
> + status = efi_call_virt(query_variable_info, attr, storage_space,
> + remaining_space, max_variable_size);
> + if (!efi_in_nmi())
> + spin_unlock_irqrestore(&efi_runtime_lock, flags);
> + return status;
> }
>
> static efi_status_t virt_efi_get_next_high_mono_count(u32 *count)
> {
> - return efi_call_virt(get_next_high_mono_count, count);
> + unsigned long flags;
> + efi_status_t status;
> +
> + BUG_ON(efi_in_nmi());
> + spin_lock_irqsave(&efi_runtime_lock, flags);
> + status = efi_call_virt(get_next_high_mono_count, count);
> + spin_unlock_irqrestore(&efi_runtime_lock, flags);
> + return status;
> }
>
> static void virt_efi_reset_system(int reset_type,
> @@ -119,17 +240,31 @@ static void virt_efi_reset_system(int reset_type,
> unsigned long data_size,
> efi_char16_t *data)
> {
> + unsigned long flags;
> +
> + if (!efi_in_nmi())
> + spin_lock_irqsave(&efi_runtime_lock, flags);
> __efi_call_virt(reset_system, reset_type, status, data_size, data);
> + if (!efi_in_nmi())
> + spin_unlock_irqrestore(&efi_runtime_lock, flags);
> }
>
> static efi_status_t virt_efi_update_capsule(efi_capsule_header_t **capsules,
> unsigned long count,
> unsigned long sg_list)
> {
> + unsigned long flags;
> + efi_status_t status;
> +
> if (efi.runtime_version < EFI_2_00_SYSTEM_TABLE_REVISION)
> return EFI_UNSUPPORTED;
>
> - return efi_call_virt(update_capsule, capsules, count, sg_list);
> + if (!efi_in_nmi())
> + spin_lock_irqsave(&efi_runtime_lock, flags);
> + status = efi_call_virt(update_capsule, capsules, count, sg_list);
> + if (!efi_in_nmi())
> + spin_unlock_irqrestore(&efi_runtime_lock, flags);
> + return status;
> }
>
> static efi_status_t virt_efi_query_capsule_caps(efi_capsule_header_t **capsules,
> @@ -137,11 +272,19 @@ static efi_status_t virt_efi_query_capsule_caps(efi_capsule_header_t **capsules,
> u64 *max_size,
> int *reset_type)
> {
> + unsigned long flags;
> + efi_status_t status;
> +
> if (efi.runtime_version < EFI_2_00_SYSTEM_TABLE_REVISION)
> return EFI_UNSUPPORTED;
>
> - return efi_call_virt(query_capsule_caps, capsules, count, max_size,
> - reset_type);
> + if (!efi_in_nmi())
> + spin_lock_irqsave(&efi_runtime_lock, flags);
> + status = efi_call_virt(query_capsule_caps, capsules, count, max_size,
> + reset_type);
> + if (!efi_in_nmi())
> + spin_unlock_irqrestore(&efi_runtime_lock, flags);
> + return status;
> }
>
> void efi_native_runtime_setup(void)
> --
> 1.8.3.2
>
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