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KVM: arm64: Avoid repetitive stack access on host EL1 to EL2 exception

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Registers x0/x1 get repeateadly pushed and poped during a host
HVC call. Instead, leave the registers on the stack, trading
a store instruction on the fast path for an add on the slow path.

Reviewed-by: Alexandru Elisei <alexandru.elisei@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
This commit is contained in:
Marc Zyngier
2020-10-24 10:56:55 +01:00
parent 29052f1b92
commit 83fa381f66
1 changed files with 3 additions and 3 deletions
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6
arch/arm64/kvm/hyp/nvhe/host.S
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@@ -13,8 +13,6 @@
.text
SYM_FUNC_START(__host_exit)
stp x0, x1, [sp, #-16]!
get_host_ctxt x0, x1
/* Store the host regs x2 and x3 */
@@ -99,13 +97,15 @@ SYM_FUNC_END(__hyp_do_panic)
mrs x0, esr_el2
lsr x0, x0, #ESR_ELx_EC_SHIFT
cmp x0, #ESR_ELx_EC_HVC64
ldp x0, x1, [sp], #16
b.ne __host_exit
ldp x0, x1, [sp] // Don't fixup the stack yet
/* Check for a stub HVC call */
cmp x0, #HVC_STUB_HCALL_NR
b.hs __host_exit
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