Commit d86de40d authored by Mark Rutland's avatar Mark Rutland Committed by Marc Zyngier
Browse files

arm64: cpufeature: upgrade hyp caps to final 



We finalize caps before initializing kvm hyp code, and any use of
cpus_have_const_cap() in kvm hyp code generates redundant and
potentially unsound code to read the cpu_hwcaps array.

A number of helper functions used in both hyp context and regular kernel
context use cpus_have_const_cap(), as some regular kernel code runs
before the capabilities are finalized. It's tedious and error-prone to
write separate copies of these for hyp and non-hyp code.

So that we can avoid the redundant code, let's automatically upgrade
cpus_have_const_cap() to cpus_have_final_cap() when used in hyp context.
With this change, there's never a reason to access to cpu_hwcaps array
from hyp code, and we don't need to create an NVHE alias for this.

This should have no effect on non-hyp code.

Signed-off-by: default avatarMark Rutland <mark.rutland@arm.com>
Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
Acked-by: default avatarWill Deacon <will@kernel.org>
Cc: David Brazdil <dbrazdil@google.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20201026134931.28246-4-mark.rutland@arm.com
parent dfc4e3f0

arch/arm64/include/asm/cpufeature.h

+24 −2
Original line number Diff line number Diff line
@@ -375,6 +375,23 @@ cpucap_multi_entry_cap_matches(const struct arm64_cpu_capabilities *entry, 
	return false;

}



static __always_inline bool is_vhe_hyp_code(void)

{

	/* Only defined for code run in VHE hyp context */

	return __is_defined(__KVM_VHE_HYPERVISOR__);

}



static __always_inline bool is_nvhe_hyp_code(void)

{

	/* Only defined for code run in NVHE hyp context */

	return __is_defined(__KVM_NVHE_HYPERVISOR__);

}



static __always_inline bool is_hyp_code(void)

{

	return is_vhe_hyp_code() || is_nvhe_hyp_code();

}



extern DECLARE_BITMAP(cpu_hwcaps, ARM64_NCAPS);

extern struct static_key_false cpu_hwcap_keys[ARM64_NCAPS];

extern struct static_key_false arm64_const_caps_ready;
@@ -444,8 +461,11 @@ static __always_inline bool cpus_have_final_cap(int num) 
}



/*

 * Test for a capability, possibly with a runtime check.

 * Test for a capability, possibly with a runtime check for non-hyp code.

 *

 * For hyp code, this behaves the same as cpus_have_final_cap().

 *

 * For non-hyp code:

 * Before capabilities are finalized, this behaves as cpus_have_cap().

 * After capabilities are finalized, this is patched to avoid a runtime check.

 *
@@ -453,7 +473,9 @@ static __always_inline bool cpus_have_final_cap(int num) 
 */

static __always_inline bool cpus_have_const_cap(int num)

{

	if (system_capabilities_finalized())

	if (is_hyp_code())

		return cpus_have_final_cap(num);

	else if (system_capabilities_finalized())

		return __cpus_have_const_cap(num);

	else

		return cpus_have_cap(num);

arch/arm64/include/asm/virt.h

+0 −12
Original line number Diff line number Diff line
@@ -83,18 +83,6 @@ static inline bool is_kernel_in_hyp_mode(void) 
	return read_sysreg(CurrentEL) == CurrentEL_EL2;

}



static __always_inline bool is_vhe_hyp_code(void)

{

	/* Only defined for code run in VHE hyp context */

	return __is_defined(__KVM_VHE_HYPERVISOR__);

}



static __always_inline bool is_nvhe_hyp_code(void)

{

	/* Only defined for code run in NVHE hyp context */

	return __is_defined(__KVM_NVHE_HYPERVISOR__);

}



static __always_inline bool has_vhe(void)

{

	/*

arch/arm64/kernel/image-vars.h

+0 −1
Original line number Diff line number Diff line
@@ -87,7 +87,6 @@ KVM_NVHE_ALIAS(__icache_flags); 
/* Kernel symbols needed for cpus_have_final/const_caps checks. */

KVM_NVHE_ALIAS(arm64_const_caps_ready);

KVM_NVHE_ALIAS(cpu_hwcap_keys);

KVM_NVHE_ALIAS(cpu_hwcaps);



/* Static keys which are set if a vGIC trap should be handled in hyp. */

KVM_NVHE_ALIAS(vgic_v2_cpuif_trap);

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