[PATCH] arm64: kvm: avoid unnecessary absolute addressing via literals

[PATCH] arm64: kvm: avoid unnecessary absolute addressing via literals

[Ard Biesheuvel]

There are a few cases in the nVHE code where we take the absolute
address of a symbol via a literal pool entry, and subsequently translate
it to another address space (PA, kimg VA, kernel linear VA, etc).
Originally, this literal was needed because we relied on a different
translation for absolute references, but this is no longer the case, so
we can simply use relative addressing instead. This removes a couple of
RELA entries pointing into the .text segment.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 arch/arm64/kvm/hyp/nvhe/host.S | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/kvm/hyp/nvhe/host.S b/arch/arm64/kvm/hyp/nvhe/host.S
index 3d613e721a75..366551594417 100644
--- a/arch/arm64/kvm/hyp/nvhe/host.S
+++ b/arch/arm64/kvm/hyp/nvhe/host.S
@@ -80,7 +80,7 @@ SYM_FUNC_START(__hyp_do_panic)
 	mov	lr, #(PSR_F_BIT | PSR_I_BIT | PSR_A_BIT | PSR_D_BIT |\
 		      PSR_MODE_EL1h)
 	msr	spsr_el2, lr
-	ldr	lr, =nvhe_hyp_panic_handler
+	adr_l	lr, nvhe_hyp_panic_handler
 	hyp_kimg_va lr, x6
 	msr	elr_el2, lr
 
@@ -125,13 +125,11 @@ alternative_else_nop_endif
 	add	sp, sp, #16
 	/*
 	 * Compute the idmap address of __kvm_handle_stub_hvc and
-	 * jump there. Since we use kimage_voffset, do not use the
-	 * HYP VA for __kvm_handle_stub_hvc, but the kernel VA instead
-	 * (by loading it from the constant pool).
+	 * jump there.
 	 *
 	 * Preserve x0-x4, which may contain stub parameters.
 	 */
-	ldr	x5, =__kvm_handle_stub_hvc
+	adr_l	x5, __kvm_handle_stub_hvc
 	hyp_pa	x5, x6
 	br	x5
 SYM_FUNC_END(__host_hvc)
-- 
2.30.2

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[PATCH] arm64: kvm: avoid unnecessary absolute addressing via literals

[Ard Biesheuvel]

There are a few cases in the nVHE code where we take the absolute
address of a symbol via a literal pool entry, and subsequently translate
it to another address space (PA, kimg VA, kernel linear VA, etc).
Originally, this literal was needed because we relied on a different
translation for absolute references, but this is no longer the case, so
we can simply use relative addressing instead. This removes a couple of
RELA entries pointing into the .text segment.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 arch/arm64/kvm/hyp/nvhe/host.S | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/kvm/hyp/nvhe/host.S b/arch/arm64/kvm/hyp/nvhe/host.S
index 3d613e721a75..366551594417 100644
--- a/arch/arm64/kvm/hyp/nvhe/host.S
+++ b/arch/arm64/kvm/hyp/nvhe/host.S
@@ -80,7 +80,7 @@ SYM_FUNC_START(__hyp_do_panic)
 	mov	lr, #(PSR_F_BIT | PSR_I_BIT | PSR_A_BIT | PSR_D_BIT |\
 		      PSR_MODE_EL1h)
 	msr	spsr_el2, lr
-	ldr	lr, =nvhe_hyp_panic_handler
+	adr_l	lr, nvhe_hyp_panic_handler
 	hyp_kimg_va lr, x6
 	msr	elr_el2, lr
 
@@ -125,13 +125,11 @@ alternative_else_nop_endif
 	add	sp, sp, #16
 	/*
 	 * Compute the idmap address of __kvm_handle_stub_hvc and
-	 * jump there. Since we use kimage_voffset, do not use the
-	 * HYP VA for __kvm_handle_stub_hvc, but the kernel VA instead
-	 * (by loading it from the constant pool).
+	 * jump there.
 	 *
 	 * Preserve x0-x4, which may contain stub parameters.
 	 */
-	ldr	x5, =__kvm_handle_stub_hvc
+	adr_l	x5, __kvm_handle_stub_hvc
 	hyp_pa	x5, x6
 	br	x5
 SYM_FUNC_END(__host_hvc)
-- 
2.30.2


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Re: [PATCH] arm64: kvm: avoid unnecessary absolute addressing via literals

[Marc Zyngier]

On Thu, 28 Apr 2022 16:03:50 +0200, Ard Biesheuvel wrote:
> There are a few cases in the nVHE code where we take the absolute
> address of a symbol via a literal pool entry, and subsequently translate
> it to another address space (PA, kimg VA, kernel linear VA, etc).
> Originally, this literal was needed because we relied on a different
> translation for absolute references, but this is no longer the case, so
> we can simply use relative addressing instead. This removes a couple of
> RELA entries pointing into the .text segment.

Applied to next, thanks!

[1/1] arm64: kvm: avoid unnecessary absolute addressing via literals
      commit: 7ee74cc7ad7ef526e4383a3a3294b7039622eb37

Cheers,

	M.
-- 
Without deviation from the norm, progress is not possible.


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Re: [PATCH] arm64: kvm: avoid unnecessary absolute addressing via literals

[Marc Zyngier]

On Thu, 28 Apr 2022 16:03:50 +0200, Ard Biesheuvel wrote:
> There are a few cases in the nVHE code where we take the absolute
> address of a symbol via a literal pool entry, and subsequently translate
> it to another address space (PA, kimg VA, kernel linear VA, etc).
> Originally, this literal was needed because we relied on a different
> translation for absolute references, but this is no longer the case, so
> we can simply use relative addressing instead. This removes a couple of
> RELA entries pointing into the .text segment.

Applied to next, thanks!

[1/1] arm64: kvm: avoid unnecessary absolute addressing via literals
      commit: 7ee74cc7ad7ef526e4383a3a3294b7039622eb37

Cheers,

	M.
-- 
Without deviation from the norm, progress is not possible.



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