Re: [PATCH] mips/kvm: Fix ABI for compatibility with 64-bit guests.

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On 05/06/2013 04:11 PM, Sanjay Lal wrote:

On May 6, 2013, at 3:39 PM, David Daney wrote:


/* for KVM_GET_REGS and KVM_SET_REGS */
+/*
+ * If Config[AT] is zero (32-bit CPU), the register contents are
+ * stored in the lower 32-bits of the struct kvm_regs fields and sign
+ * extended to 64-bits.
+ */
struct kvm_regs {
-	__u32 gprs[32];
-	__u32 hi;
-	__u32 lo;
-	__u32 pc;
+	/* out (KVM_GET_REGS) / in (KVM_SET_REGS) */
+	__u64 gpr[32];
+	__u64 hi, lo;
+	__u64 pc;
+};

-	__u32 cp0reg[N_MIPS_COPROC_REGS][N_MIPS_COPROC_SEL];

Hi David, I'll try out the diff with QEMU and confirm that it works as expected. Could you just leave the GPR field in kvm_regs as "gprs". Its a minor change but avoids diffs that just replace "gprs" with "gpr".


Well, there were two changes with respect to 'gprs' vs. 'gpr'.

The change you show above only results in a small handful of diff lines.

My argument for the change is that it will be part of a public ABI, and should be short and concise, so I changed it to 'gpr'.

I also changed the field with the same name in struct kvm_vcpu_arch to match, which causes the changes in asm-offsets.c and quite a few other places as well. One could argue that this one was gratuitous, but I thought it would be nice for them to match. Since it is an internal implementation detail, it is not that important, so I could revert this part if there are strong objections.

David Daney



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