From: Juergen Gross via Virtualization <virtualization@lists.linux-foundation.org>
To: Jan Beulich <jbeulich@suse.com>, Deep Shah <sdeep@vmware.com>,
"VMware, Inc." <pv-drivers@vmware.com>
Cc: Linux Virtualization <virtualization@lists.linux-foundation.org>
Subject: Re: [PATCH] x86/paravirt: use %rip-relative addressing in hook calls
Date: Tue, 5 Oct 2021 09:43:18 +0200 [thread overview]
Message-ID: <ba01c739-cda3-cc39-af5b-225d20c20a1e@suse.com> (raw)
In-Reply-To: <b8192e8a-13ef-6ac6-6364-8ba58992cd1d@suse.com>
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On 30.09.21 14:40, Jan Beulich via Virtualization wrote:
> While using a plain (constant) address works, its use needlessly invokes
> a SIB addressing mode, making every call site one byte larger than
> necessary. Instead of using an "i" constraint with address-of operator
> and a 'c' operand modifier, simply use an ordinary "m" constraint, which
> the 64-bit compiler will translate to %rip-relative addressing. This way
> we also tell the compiler the truth about operand usage - the memory
> location gets actually read, after all.
>
> 32-bit code generation is unaffected by the change.
>
> Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Juergen
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next prev parent reply other threads:[~2021-10-05 7:43 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-30 12:40 [PATCH] x86/paravirt: use %rip-relative addressing in hook calls Jan Beulich via Virtualization
2021-10-05 7:43 ` Juergen Gross via Virtualization [this message]
2021-11-23 9:29 ` Jan Beulich via Virtualization
2021-11-23 9:52 ` Juergen Gross via Virtualization
2022-01-10 13:26 ` Juergen Gross via Virtualization
2022-01-10 19:31 ` Borislav Petkov
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