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Commit cedbb8b7 authored by Marc Zyngier's avatar Marc Zyngier
Browse files

arm64: KVM: VHE: Patch out kern_hyp_va 



The kern_hyp_va macro is pretty meaninless with VHE, as there is
only one mapping - the kernel one.

In order to keep the code readable and efficient, use runtime
patching to replace the 'and' instruction used to compute the VA
with a 'nop'.

Reviewed-by: default avatarChristoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: default avatarMarc Zyngier <marc.zyngier@arm.com>
parent b81125c7

arch/arm64/include/asm/kvm_mmu.h

+11 −1
Original line number Diff line number Diff line
@@ -23,13 +23,16 @@ 
#include <asm/cpufeature.h>



/*

 * As we only have the TTBR0_EL2 register, we cannot express

 * As ARMv8.0 only has the TTBR0_EL2 register, we cannot express

 * "negative" addresses. This makes it impossible to directly share

 * mappings with the kernel.

 *

 * Instead, give the HYP mode its own VA region at a fixed offset from

 * the kernel by just masking the top bits (which are all ones for a

 * kernel address).

 *

 * ARMv8.1 (using VHE) does have a TTBR1_EL2, and doesn't use these

 * macros (the entire kernel runs at EL2).

 */

#define HYP_PAGE_OFFSET_SHIFT	VA_BITS

#define HYP_PAGE_OFFSET_MASK	((UL(1) << HYP_PAGE_OFFSET_SHIFT) - 1)
@@ -56,12 +59,19 @@ 


#ifdef __ASSEMBLY__



#include <asm/alternative.h>

#include <asm/cpufeature.h>



/*

 * Convert a kernel VA into a HYP VA.

 * reg: VA to be converted.

 */

.macro kern_hyp_va	reg

alternative_if_not ARM64_HAS_VIRT_HOST_EXTN	

	and	\reg, \reg, #HYP_PAGE_OFFSET_MASK

alternative_else

	nop

alternative_endif

.endm



#else

arch/arm64/kvm/hyp/hyp.h

+22 −3
Original line number Diff line number Diff line
@@ -25,9 +25,28 @@ 


#define __hyp_text __section(.hyp.text) notrace



#define kern_hyp_va(v) (typeof(v))((unsigned long)(v) & HYP_PAGE_OFFSET_MASK)

#define hyp_kern_va(v) (typeof(v))((unsigned long)(v) - HYP_PAGE_OFFSET \

						      + PAGE_OFFSET)

static inline unsigned long __kern_hyp_va(unsigned long v)

{

	asm volatile(ALTERNATIVE("and %0, %0, %1",

				 "nop",

				 ARM64_HAS_VIRT_HOST_EXTN)

		     : "+r" (v) : "i" (HYP_PAGE_OFFSET_MASK));

	return v;

}



#define kern_hyp_va(v) (typeof(v))(__kern_hyp_va((unsigned long)(v)))



static inline unsigned long __hyp_kern_va(unsigned long v)

{

	u64 offset = PAGE_OFFSET - HYP_PAGE_OFFSET;

	asm volatile(ALTERNATIVE("add %0, %0, %1",

				 "nop",

				 ARM64_HAS_VIRT_HOST_EXTN)

		     : "+r" (v) : "r" (offset));

	return v;

}



#define hyp_kern_va(v) (typeof(v))(__hyp_kern_va((unsigned long)(v)))



/**

 * hyp_alternate_select - Generates patchable code sequences that are