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From: "Daniel P. Smith" <dpsmith@apertussolutions.com>
To: Andrew Cooper <andrew.cooper3@citrix.com>,
	Xen-devel <xen-devel@lists.xenproject.org>
Cc: Jan Beulich <jbeulich@suse.com>, Daniel De Graaf <dgdegra@tycho.nsa.gov>
Subject: Re: [PATCH 1/5] x86/altcall: allow compound types to be passed
Date: Fri, 5 Nov 2021 10:09:05 -0400	[thread overview]
Message-ID: <7353d569-5baf-1ecb-3fcd-31a3b4f5874a@apertussolutions.com> (raw)
In-Reply-To: <20211105135555.24261-2-andrew.cooper3@citrix.com>


On 11/5/21 9:55 AM, Andrew Cooper wrote:
> From: Jan Beulich <jbeulich@suse.com>
> 
> Replace the conditional operator in ALT_CALL_ARG(), which was intended
> to limit usable types to scalar ones, by a size check. Some restriction
> here is necessary to make sure we don't violate the ABI's calling
> conventions, but limiting to scalar types was both too restrictive
> (disallowing e.g. guest handles) and too permissive (allowing e.g.
> __int128_t).
> 
> Note that there was some anomaly with that conditional operator anyway:
> Something - I don't recall what - made it impossible to omit the middle
> operand.
> 
> Code-generation-wise this has the effect of removing certain zero- or
> sign-extending in some altcall invocations. This ought to be fine as the
> ABI doesn't require sub-sizeof(int) values to be extended, except when
> passed through an ellipsis. No functions subject to altcall patching has
> a variable number of arguments, though.
> 
> Requested-by: Andrew Cooper <andrew.cooper3@citrix.com>
> Signed-off-by: Jan Beulich <jbeulich@suse.com>
> Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>
> 

Reviewed-by: Daniel P. Smith <dpsmith@apertussolutions.com>


  reply	other threads:[~2021-11-05 14:11 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-11-05 13:55 [PATCH 0/5] XSM: cleanups Andrew Cooper
2021-11-05 13:55 ` [PATCH 1/5] x86/altcall: allow compound types to be passed Andrew Cooper
2021-11-05 14:09   ` Daniel P. Smith [this message]
2021-11-05 13:55 ` [PATCH 2/5] xen/xsm: Complete altcall conversion of xsm interface Andrew Cooper
2021-11-05 14:00   ` Jan Beulich
2021-11-05 14:11   ` Daniel P. Smith
2021-11-08  9:11   ` Jan Beulich
2021-11-17 22:22     ` Andrew Cooper
2021-11-05 13:55 ` [PATCH 3/5] xen/xsm: Drop xsm_hvm_control() hook Andrew Cooper
2021-11-05 14:20   ` Daniel P. Smith
2021-11-05 13:55 ` [PATCH 4/5] xen/xsm: Improve fallback handling in xsm_fixup_ops() Andrew Cooper
2021-11-05 14:22   ` Daniel P. Smith
2021-11-08  9:04   ` Jan Beulich
2021-11-17 22:37     ` Andrew Cooper
2021-11-18 11:59       ` Jan Beulich
2021-11-05 13:55 ` [PATCH 5/5] xen/xsm: Address hypercall ABI problems Andrew Cooper
2021-11-08  9:50   ` Jan Beulich
2021-11-17 23:14     ` Andrew Cooper
2021-11-17 23:20       ` Andrew Cooper
2021-11-18 13:01         ` Jan Beulich
2021-11-18 12:59       ` Jan Beulich

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