From mboxrd@z Thu Jan 1 00:00:00 1970 From: arnd@arndb.de (Arnd Bergmann) Date: Thu, 1 Dec 2011 15:42:19 +0000 Subject: [Android-virt] [Embeddedxen-devel] [Xen-devel] [ANNOUNCE] Xen port to Cortex-A15 / ARMv7 with virt extensions In-Reply-To: <20111201151043.GG27394@arm.com> References: <1322735197.31810.191.camel@zakaz.uk.xensource.com> <20111201151043.GG27394@arm.com> Message-ID: <201112011542.19377.arnd@arndb.de> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Thursday 01 December 2011, Catalin Marinas wrote: > Given the way register banking is done on AArch64, issuing an HVC on a > 32-bit guest OS doesn't require translation on a 64-bit hypervisor. We > have a similar implementation at the SVC level (for 32-bit user apps on > a 64-bit kernel), the only modification was where a 32-bit SVC takes a > 64-bit parameter in two separate 32-bit registers, so packing needs to > be done in a syscall wrapper. How do you deal with signed integer arguments passed into SVC or HVC from a caller? If I understand the architecture correctly, the upper halves of the argument register end up zero-padded, while the callee expects sign-extension. Arnd