Re: [PATCH v4 13/34] KVM: arm64: Enable access to sanitized CPU features at EL2

On Fri, Mar 12, 2021 at 06:34:09AM +0000, Quentin Perret wrote:

On Thursday 11 Mar 2021 at 19:36:39 (+0000), Will Deacon wrote:

quoted

On Wed, Mar 10, 2021 at 05:57:30PM +0000, Quentin Perret wrote:

quoted

diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 4f2f1e3145de..84be93df52fa 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c

@@ -21,6 +21,7 @@
 #include <asm/debug-monitors.h>
 #include <asm/esr.h>
 #include <asm/kvm_arm.h>
+#include <asm/kvm_cpufeature.h>
 #include <asm/kvm_emulate.h>
 #include <asm/kvm_hyp.h>
 #include <asm/kvm_mmu.h>

@@ -2775,3 +2776,23 @@ void kvm_sys_reg_table_init(void)
 	/* Clear all higher bits. */
 	cache_levels &= (1 << (i*3))-1;
 }
+
+#undef KVM_HYP_CPU_FTR_REG
+#define KVM_HYP_CPU_FTR_REG(id, name) \
+	{ .sys_id = id, .dst = (struct arm64_ftr_reg *)&kvm_nvhe_sym(name) },
+struct __ftr_reg_copy_entry {
+	u32			sys_id;
+	struct arm64_ftr_reg	*dst;
+} hyp_ftr_regs[] __initdata = {
+	#include <asm/kvm_cpufeature.h>
+};

This looks a bit elaborate to me. Why can't you just spell things out here
like:

#define KVM_HYP_CPU_FTR_REG(id, name) \
	{ .sys_id = id, .dst = (struct arm64_ftr_reg *)&kvm_nvhe_sym(name) }

struct __ftr_reg_copy_entry {
	u32			sys_id;
	struct arm64_ftr_reg	*dst;
} hyp_ftr_regs[] __initdata = {
	KVM_HYP_CPU_FTR_REG(SYS_CTR_EL0, arm64_ftr_reg_ctrel0),
	...
};

and then have the header file be a normal, guarded header which just
declares these things? The id parameter to the macro isn't used there.

I just tried to reduce the boilerplate as much as possible -- in the
current form you only need to add additional features to the header
it'll 'just work'.

I don't really think it's worth it -- people are used to having to add
declarations for things, so keeping it simple should be fine.

Will

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