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KVM: arm64: Define our own swab32() to avoid a uapi static inline

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KVM uses swab32() when mediating GIC MMIO accesses if the GICV is badly
aligned, and the host and guest differ in endianness.

arm64 doesn't provide a __arch_swab32(), so __fswab32() is always backed
by the macro implementation that the compiler reduces to a single
instruction. But the static-inline causes problems for KVM if the compiler
chooses not to inline this function, it may not be located in the
__hyp_text where __vgic_v2_perform_cpuif_access() needs it.

Create our own __kvm_swab32() macro that calls ___constant_swab32()
directly. This way we know it will always be inlined.

Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20200220165839.256881-3-james.morse@arm.com
This commit is contained in:
James Morse 2020-02-20 16:58:38 +00:00 committed by Marc Zyngier
parent 5c37f1ae1c
commit 8c2d146ee7
2 changed files with 9 additions and 2 deletions
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7
arch/arm64/include/asm/kvm_hyp.h
View File

@ -47,6 +47,13 @@
#define read_sysreg_el2(r) read_sysreg_elx(r, _EL2, _EL1)
#define write_sysreg_el2(v,r) write_sysreg_elx(v, r, _EL2, _EL1)
/*
* Without an __arch_swab32(), we fall back to ___constant_swab32(), but the
* static inline can allow the compiler to out-of-line this. KVM always wants
* the macro version as its always inlined.
*/
#define __kvm_swab32(x) ___constant_swab32(x)
int __vgic_v2_perform_cpuif_access(struct kvm_vcpu *vcpu);
void __vgic_v3_save_state(struct kvm_vcpu *vcpu);

4
arch/arm64/kvm/hyp/vgic-v2-cpuif-proxy.c
View File

@ -69,14 +69,14 @@ int __hyp_text __vgic_v2_perform_cpuif_access(struct kvm_vcpu *vcpu)
u32 data = vcpu_get_reg(vcpu, rd);
if (__is_be(vcpu)) {
/* guest pre-swabbed data, undo this for writel() */
data = swab32(data);
data = __kvm_swab32(data);
}
writel_relaxed(data, addr);
} else {
u32 data = readl_relaxed(addr);
if (__is_be(vcpu)) {
/* guest expects swabbed data */
data = swab32(data);
data = __kvm_swab32(data);
}
vcpu_set_reg(vcpu, rd, data);
}