From: Richard Henderson Date: Sat, 12 Apr 2025 16:43:15 +0000 (-0700) Subject: docs: Document removal of 64-bit on 32-bit emulation X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=f3ca7ca22271ac7c1b997092d72ad36517618fb5;p=people%2Faperard%2Fqemu-dm.git docs: Document removal of 64-bit on 32-bit emulation With acce728cbc6c we disallowed configuring 64-bit guests on 32-bit hosts, but forgot to document that in removed-features. Signed-off-by: Richard Henderson Reviewed-by: Michael Tokarev Reviewed-by: Daniel P. Berrangé Reviewed-by: Alex Bennée Signed-off-by: Michael Tokarev --- diff --git a/docs/about/removed-features.rst b/docs/about/removed-features.rst index 2527a91795..790a5e481c 100644 --- a/docs/about/removed-features.rst +++ b/docs/about/removed-features.rst @@ -858,6 +858,15 @@ QEMU. Since all recent x86 hardware from the past >10 years is capable of the 64-bit x86 extensions, a corresponding 64-bit OS should be used instead. +32-bit hosts for 64-bit guests (removed in 10.0) +'''''''''''''''''''''''''''''''''''''''''''''''' + +In general, 32-bit hosts cannot support the memory space or atomicity +requirements of 64-bit guests. Prior to 10.0, QEMU attempted to +work around the atomicity issues in system mode by running all vCPUs +in a single thread context; in user mode atomicity was simply broken. +From 10.0, QEMU has disabled configuration of 64-bit guests on 32-bit hosts. + Guest Emulator ISAs -------------------