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[78.146.248.75]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-493e0f4e3afsm88611485e9.7.2026.07.07.12.49.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 07 Jul 2026 12:49:23 -0700 (PDT) X-Outflank-Mailman: Message body and most headers restored to incoming version X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" Authentication-Results: eu.smtp.expurgate.cloud; dkim=pass header.s=google header.d=citrix.com header.i="@citrix.com" header.h="Content-Transfer-Encoding:Content-Type:MIME-Version:Message-Id:Date:Subject:Cc:To:From" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=citrix.com; s=google; t=1783453764; x=1784058564; darn=lists.xenproject.org; h=content-transfer-encoding:content-type:mime-version:message-id:date :subject:cc:to:from:from:to:cc:subject:date:message-id:reply-to :content-type; bh=GNAZh+YVrrF3CVOLHqSmEARVfm8tjKj1UJEXvh4756w=; b=lMZ0bh4CQjWdQGnVZBvGlweWtHArQMUzGAlFcZ+srslrUELPG2prPF9lrYKcOZzuxT A8JxrNxw0PXxL+/LXLrXp3cD8NAHWjuU3NUkzA8oNUZH0S4sCI8JpX7ZXQ3732gdk32r u2q+ju8X5u208HIxpc2TnLmwfmzQUrDnwGIPk= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1783453764; x=1784058564; h=content-transfer-encoding:content-type:mime-version:message-id:date :subject:cc:to:from:x-gm-gg:x-gm-message-state:from:to:cc:subject :date:message-id:reply-to:content-type; bh=GNAZh+YVrrF3CVOLHqSmEARVfm8tjKj1UJEXvh4756w=; b=MOBPU8bq2KhuhcPI/MuyW5ToTC/qP75k/vq/TPQsMaV9ezcQLdeDb4sBYGeWrL8cSw MeRGdPZAwoqpavb5oqOJITYOFzNmhRCOM8mv3Kd7dGDVfL2irERs0YBqbt5JUL+ZA8K4 tChS0XD3bpEsPlWabcucjyrRYW8Wxyfqswf9Wksq9O1Cxh0Si+Rwlw5wMQM6t/2xbCdr h2qSbXhIfzvb2K8Lz6LszeMoRrwialnGPHQnOL5rkEchMJK+NuSzgjWfQufNra+j8W97 Z1j56LED+wMRnIjMcoyDkK5Zeh93HgdBJr7jbIiQFGlPhXRMXqQzJb4pETMcCJj69rvh Jbjw== X-Gm-Message-State: AOJu0YwXIUWks+7nnkASpSWN9ZUG+DsG8j3nqP4XIMSDhiVtKHxww3pn VFGSGNex4Sgq/geqmi0hEQaAEFXqN28eNnviKvJKdWzHy8hgF9JRxR0Z85Hn3xy7cvnwyv20vhO hZaC6faQ= X-Gm-Gg: AfdE7cmvWvnEfVrv5DaPHTwCxMa8sgH/YGkK0nrd2Nsh7MPeD/Z3oLQfAyMNEVp8vln qA+FkB2arUJI4lOCbUtNptWxmFyZ3ClGea/QNfEsrYSnOQwWTH5aFI1purALR6ydhREFdGWyNVC Ebka7SvavJP9pBOx9HCMkoqbrtdL32Pt1Gs7mnszfczt5Ms34sQJ1ffkvlF/UEAxwKKKONAX0Ih QJ9YRdl48rNYiqmZJQI0wJakT+WMLRPjmOnZTxnHb4ZxClRbbiN7vXqj6csJgh26Q0qPx1nB60U mM+DmQHMzgzj5UgkaZX5U0QUXw3v6SQBopZb/SkD5ms248w0Xnr3K/nJTwWRYfqSJKxfWfZ8mcW 7DAHFahqD65Li/gduhLGhcHIPu98xMBVPPTkp75VhjkfRi9eLDXu8oAJ5HVqWgh5Ti4K+po4IfF 15+Untuz7NnA/hdFh+Uz+njcT3m9zU7hapu1xmOw4yLqIP2zxeJTMNRtrW3iqbINk= X-Received: by 2002:a05:600c:6990:b0:492:3fb5:3a17 with SMTP id 5b1f17b1804b1-493e17dda4dmr42962095e9.2.1783453763929; Tue, 07 Jul 2026 12:49:23 -0700 (PDT) From: Andrew Cooper To: Xen-devel Cc: Andrew Cooper , Jan Beulich , =?UTF-8?q?Roger=20Pau=20Monn=C3=A9?= , Teddy Astie Subject: [PATCH v3] x86/emul: Adjust handling of CR8_LEGACY Date: Tue, 7 Jul 2026 20:49:21 +0100 Message-Id: <20260707194921.1425926-1-andrew.cooper3@citrix.com> X-Mailer: git-send-email 2.39.5 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-purgate-ID: tlsNG-ebf023/1783453764-ADD341CC-F93BA89E/0/0 X-purgate-type: clean X-purgate-size: 1470 X-ZohoMail-DKIM: pass (identity @citrix.com) X-ZM-MESSAGEID: 1783453790898158500 The APM description of the AltMovCR8 feature bit is: "LOCK MOV CR0 means MOV CR8" Adjust the decode logic to behave like this. Signed-off-by: Andrew Cooper Reviewed-by: Jan Beulich Reviewed-by: Teddy Astie --- CC: Jan Beulich CC: Roger Pau Monn=C3=A9 CC: Teddy Astie v3: * Change yet again. A contact with information on the matter confirmed th= at it is a special case for Reg =3D 0, and not a general modifier to all Reg values. --- xen/arch/x86/x86_emulate/decode.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/xen/arch/x86/x86_emulate/decode.c b/xen/arch/x86/x86_emulate/d= ecode.c index 2c13356c4d17..57f6baffb066 100644 --- a/xen/arch/x86/x86_emulate/decode.c +++ b/xen/arch/x86/x86_emulate/decode.c @@ -780,12 +780,12 @@ decode_twobyte(struct x86_emulate_state *s, break; =20 case 0x20: case 0x22: /* mov to/from cr */ - if ( s->lock_prefix && vcpu_has_cr8_legacy() ) + if ( s->lock_prefix && vcpu_has_cr8_legacy() && s->modrm_reg =3D= =3D 0 ) { - s->modrm_reg +=3D 8; + s->modrm_reg =3D 8; s->lock_prefix =3D false; } - /* fall through */ + fallthrough; case 0x21: case 0x23: /* mov to/from dr */ ASSERT(s->ea.type =3D=3D OP_REG); /* Early operand adjustment ensu= res this. */ generate_exception_if(s->lock_prefix, X86_EXC_UD); --=20 2.39.5