[Top] [All Lists]

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

To: Sanjay Lal <>
Subject: Re: [PATCH] mips/kvm: Fix ABI for compatibility with 64-bit guests.
From: David Daney <>
Date: Mon, 06 May 2013 16:28:07 -0700
Cc:,,,, David Daney <>
Dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed;; s=20120113; h=x-received:message-id:date:from:user-agent:mime-version:to:cc :subject:references:in-reply-to:content-type :content-transfer-encoding; bh=RDp6cgaximA/YJP/RYDF15AuYJGIGCuLAvNlze/WXeE=; b=tsJn8NyJfpGigeNuKVrzzPH2/uUEIbKtP+8Tydvp/9VOW0C0eAvPuregHgTb4FHDwG 0lSBqwDbFIFnH22MfpcBAGgkYadq9wVNwtX4ObdyW6zzDwTjGBTreFV6sERNiafgPPuC oG1jKlxlEO5/7dY5xpN5eYeLZWXH1IoOHYNpgYuLxvKr9iSikXdtCCQ6L8spqFptTlNs iU3dAqMKZyAlGItxw6vvjLyCm/2k2gIO4F+yOTZJb+LF6yXExkb1bRGiVXKK6baNctEA LvCtPt40l59k1LoKk2NfRNSOhmanGNQinalzNAvjuwIVunoMSrNc0vnBPGbF5b2TttmX Xang==
In-reply-to: <>
List-archive: <>
List-help: <>
List-id: linux-mips <>
List-owner: <>
List-post: <>
List-software: Ecartis version 1.0.0
List-subscribe: <>
List-unsubscribe: <>
Original-recipient: rfc822;
References: <> <>
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130311 Thunderbird/17.0.4
On 05/06/2013 04:11 PM, Sanjay Lal wrote:

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

+ * 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

<Prev in Thread] Current Thread [Next in Thread>