From: Dave Hansen <dave.hansen@intel.com>
To: Uros Bizjak <ubizjak@gmail.com>,
x86@kernel.org, linux-kernel@vger.kernel.org
Cc: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
"H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [PATCH] x86/acrn: Improve ACRN hypercalls
Date: Thu, 4 Aug 2022 11:41:36 -0700 [thread overview]
Message-ID: <91ccae0b-6135-6163-f59b-4e99624090a5@intel.com> (raw)
In-Reply-To: <20220804180358.32944-1-ubizjak@gmail.com>
On 8/4/22 11:03, Uros Bizjak wrote:
> As explained in section 6.47.5.2, "Specifying Registers for Local Variables"
> of the GCC info documentation, the correct way to specify register for
> input operands when calling Extended 'asm' is to define a local register
> variable and associate it with a specified register:
>
> register unsigned long r8 asm ("r8") = hcall_id;
IIRC, that's what the ACRN folks proposed first. But, it's more fragile
because you can't, for instance, put a printk() in that function between
the variable definition and assebly.
next prev parent reply other threads:[~2022-08-04 18:41 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-04 18:03 Uros Bizjak
2022-08-04 18:41 ` Dave Hansen [this message]
2022-08-04 18:56 ` Uros Bizjak
2022-08-04 19:03 ` Dave Hansen
2022-08-08 18:59 ` H. Peter Anvin
2022-08-04 18:52 ` Sean Christopherson
2022-08-04 19:05 ` Uros Bizjak
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